Symmetrical magnetic head and magnetic media for use with such head

Abstract

An apparatus, in accordance with one aspect of the present invention, includes a magnetic head having an array of transducers, the transducers comprising data elements, at least two first servo readers positioned toward a first end of the array and at least two second servo readers positioned toward a second end of the array. The array is symmetrical about a centerpoint of the array, such that a distance between a center of an innermost one of the first servo readers and a center of the data element closest thereto is the same as a distance between a center of an innermost one of the second servo readers and a center of the data element closest thereto, and such that a distance between a center of an outermost one of the first servo readers and the center of the data element closest thereto is the same as a distance between a center of an outermost one of the second servo readers and the center of the data element closest thereto.

Description

SYMMETRICAL MAGNETIC HEAD AND MAGNETIC MEDIA FOR USE WITH SUCH HEAD BACKGROUND

[0001] The present invention relates to data storage systems, and more particularly, thisinvention relates to a new magnetic head design and corresponding magnetic recording tape media.

[0002] In magnetic storage systems, magnetic transducers, also referred to as “elements,”read data from and write data onto magnetic recording media. Data is written on the magneticrecording media by moving a magnetic recording transducer to a position over the media wherethe data is to be stored. The magnetic recording transducer then generates a magnetic field,which encodes the data into the magnetic media. Data is read from the media by similarlypositioning the magnetic read transducer and then sensing the magnetic field of the magneticmedia. Read and write operations may be independently synchronized with the movement of the media to ensure that the data can be read from and written to the desired location on the media.

[0003] An important and continuing goal in the data storage industry is that of increasingthe density of data stored on a medium. For tape storage systems, that goal has led toincreasing the track and linear bit density on recording tape, and decreasing the thickness ofthe magnetic tape medium. However, the development of small footprint, higherperformance tape drive systems has created various challenges ranging from the design oftape head assemblies for use in such systems to dealing with tape dimensional instability.

[0004] Storing data on recording tape media is a low-cost approach to storing large scaledata. However, the cost of developing the media for a given format is expensive. Increasing theusage of recording area on magnetic media lowers the overall cost of data storage, and istherefore a desirable goal. SUMMARY

[0005] An apparatus, in accordance with one aspect of the present invention, includes amagnetic head having an array of transducers, the transducers comprising data elements, at least two first servo readers positioned toward a first end of the array and at least two second servo readers positioned toward a second end of the array. The array is symmetrical about a centerpoint of the array, such that a distance between a center of an innermost one of the firstservo readers and a center of the data element closest thereto is the same as a distancebetween a center of an innermost one of the second servo readers and a center of the dataelement closest thereto, and such that a distance between a center of an outermost one of the first servo readers and the center of the data element closest thereto is the same as a distance between a center of an outermost one of the second servo readers and the center of the data element closest thereto.

[0006] An apparatus, in accordance with one approach, includes a drive mechanism forpassing a magnetic tape over the magnetic head, and a controller electrically coupled to themagnetic head.

[0007] An apparatus, in accordance with another general embodiment, includes amagnetic head having an array of transducers and a second array of transducers aligned along a longitudinal axis of the array, wherein a first end of the second array is positioned adjacent the array. The array comprises data elements, at least two first servo readers positioned toward a first end of the array and at least two second servo readers positioned toward a second end of the array. The second array includes second data elements and at least two third servo readers positioned toward a second end of the second array. The array is symmetrical about a centerpoint thereof, such that a distance between a center of an innermost one of the first servo readers and a center of the data element closest thereto is the same as a distance between a center of an innermost one of the second servo readers and a center of the data element closest thereto, and such that a distance between a center of anoutermost one of the first servo readers and the center of the data element closest thereto isthe same as a distance between a center of an outermost one of the second servo readers and the center of the data element closest thereto. A distance between the center of the innermost second servo reader and a center of the data element of the second array closest thereto is the same as the distance between the center of the outermost first servo reader and the center of the data element closest thereto. A distance between a center of the outermost second servo reader and a center of the data element of the second array closest thereto is the same as the distance between the center of the innermost second servo reader and the center of the data element closest thereto.

[0008] Any of these approaches may be implemented in a magnetic data storage systemsuch as a tape drive system, which may include a magnetic head, a drive mechanism for passing a magnetic medium (e.g., recording tape) over the magnetic head, and a controller electrically coupled to the magnetic head.

[0009] A product, in accordance with one aspect of the present invention, includes amagnetic tape having a plurality of servo bands extending along a longitudinal axis of the magnetic tape. A width WSB.Tape of each of the servo bands satisfies the following equation:^ W^^.^^^^~^^.^^^^^ , to an accuracy of 10%, where: WEP.Tapeis an average pitch of elements on the head used to read and write data and is given as.where: ^^is the number of elements used to write each data band, ^^^is the number of databands specified by a format of the magnetic tape, WEdge is a width of an edge band of the magnetic tape where no data and no servo pattern is written as specified by the format, and WTape is a width of the magnetic tape.

[0010] Other aspects of the present invention will become apparent from the followingdetailed description, which, when taken in conjunction with the drawings, illustrate by way of example the principles of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 is a diagram of a computing environment, in accordance with one aspectof the present invention.

[0012] FIG. 2A is a schematic diagram of a simplified tape drive system, in accordance withone aspect.

[0013] FIG. 2B is a schematic diagram of a tape cartridge, in accordance with one aspect.

[0014] FIG. 2C illustrates a side view of a flat-lapped, bi-directional, two-module magnetictape head, in accordance with one aspect.

[0015] FIG. 2D is a tape bearing surface view taken from Line 2D of FIG. 2C.

[0016] FIG. 2E is a detailed view taken from Circle 2E of FIG. 2D.

[0017] FIG. 2F is a detailed view of a partial tape bearing surface of a pair of modules.

[0018] FIG. 3 is a partial tape bearing surface view of a magnetic head having a write-read-write configuration, in accordance with one aspect.

[0019] FIG. 4 is a partial tape bearing surface view of a magnetic head having a read-write-read configuration, in accordance with one aspect.

[0020] FIG. 5 is a side view of a magnetic tape head with three modules where themodules all generally lie along about parallel planes, in accordance with one aspect.

[0021] FIG. 6 is a side view of a magnetic tape head with three modules in a tangent(angled) configuration, in accordance with one aspect.

[0022] FIG. 7 is a side view of a magnetic tape head with three modules in an overwrapconfiguration.

[0023] FIGS. 8A-8C are schematics depicting the principles of tape tenting.

[0024] FIG. 9 is a representational diagram of files and indexes stored on a magnetic tape, inaccordance with one aspect.

[0025] FIG. 10 is a partial representative view of a magnetic tape formatted according to theLTO 10 format.

[0026] FIG. 11 is representational view of regions on a magnetic tape, according to aconventional format.

[0027] FIG. 12 is a representational view of data band and sub-data band composition, inaccordance with an exemplary approach.

[0028] FIG. 13 is a schematic of the servo bands and a single sub data band for forward andreverse writing and reading, in accordance with an exemplary approach.

[0029] FIG. 14 is a schematic of the servo bands and a two sub data bands for one servoreader per servo band for the case where ^^ = 3 and ^^^ = 2, in accordance with anexemplary approach.

[0030] FIG. 15 is a schematic of a single band head with dual servo readers per servo band,in accordance with an exemplary approach.

[0031] FIG. 16A is a schematic of servo bands and a single sub data band for forwardwriting and reading utilizing servo readers ^^^and ^^^, in accordance with an exemplary approach.

[0032] FIG. 16B is a schematic of servo bands and a single sub data band for reverse writingand reading utilizing servo readers ^^^and ^^^, in accordance with an exemplary approach.

[0033] FIG. 17 is a schematic of a 1-band head with ^^ elements utilizing a Dual ServoOption for a 3-module head alignment with Left Writer (LW), Right Writer (RW) and Center Reader (CR) modules, in accordance with an exemplary approach.

[0034] FIG. 18 is a schematic of a 2-band head with ^^ elements in each of two groups oftransducers, and utilizing a Dual Servo Option for a 3-module head alignment with LW, RW and CR modules, in accordance with an exemplary approach.

[0035] FIG. 19 is a schematic of a 1-band head with ^^ elements utilizing a Dual ServoOption for a 2-module head alignment, in accordance with an exemplary approach.

[0036] FIG. 20A is a schematic for a 1-band head with ^^ elements utilizing Dual ServoOption for a 3-module head alignment with LW, RW and CR modules, in accordance with one approach in which writer pole P2 is the trailing edge.

[0037] FIG. 20B is a schematic for a 1-band head with ^^ elements utilizing Dual ServoOption for a 3-module head alignment with LW, RW and CR modules, in accordance with one approach in which writer pole P1 is the trailing edge.

[0038] FIG. 21 is a schematic of a tilted head concept for tape dimensional stability (TDS)compensation, in accordance with an exemplary approach.

[0039] FIG. 22 is a schematic of a head chip with a dual-band head design with two servoreaders per band taken in the reference frame of the tape, in accordance with an exemplary approach.

[0040] FIG. 23 is a schematic of the alignment on a module of a dual-band head withtwo servo readers per band for use in a tape drive with, as shown in part (a), 1-band of ^^channels, and as shown in part (b), 2-bands of ^^^^ channels.

[0041] FIG. 24 is a schematic of the alignment on a module of a dual-band head withtwo servo readers per band for use in a tape drive with 1-band of ^^channels using only Group 1 data elements aligned at operation at far ends of operation.

[0042] FIG. 25 is a schematic of the alignment on a module of a dual-band head withtwo servo readers per band for use in a tape drive with 2-band of ^^^^channels (^^per Group), with the data elements aligned at operation at far ends of operation. DETAILED DESCRIPTION

[0043] The following description is made for the purpose of illustrating the generalprinciples of the present invention and is not meant to limit the inventive concepts claimedherein. Further, particular features described herein can be used in combination with otherdescribed features in each of the various possible combinations and permutations.

[0044] Unless otherwise specifically defined herein, all terms are to be given theirbroadest possible interpretation including meanings implied from the specification as well asmeanings understood by those skilled in the art and / or as defined in dictionaries, treatises,etc.

[0045] It must also be noted that, as used in the specification and the appended claims,the singular forms "a," "an" and "the" include plural referents unless otherwise specified.

[0046] The following description discloses several preferred aspects of magnetic-media-based data storage systems, as well as operation and / or component parts thereof. Variousapproaches include an apparatus symmetrical transducer (element) layout, with two servoreaders positioned one each side of an array of data elements. Magnetic tape media for use with such apparatus is also described.

[0047] An apparatus, in accordance with one aspect of the present invention, includes amagnetic head having an array of transducers, the transducers comprising data elements such as read elements or write elements, at least two first servo readers positioned toward a first end of the array and at least two second servo readers positioned toward a second end of the array. The servo readers are preferably generally aligned with the data elements along the longitudinal axis of the array, and are positioned relative to the data elements to enable positioning of the data elements within a data band of a magnetic tape based on readback signals from at least some of the servo readers reading the servo bands that flank the data band. The array is symmetrical about a centerpoint of the array, such that a distance between a center of an innermost one of the first servo readers and a center of the data element closest thereto is the same as a distance between a center of an innermost one of the second servo readers and a center of the data element closest thereto, and such that a distance between a center of an outermost one of the first servo readers and the center of the data element closest thereto is the same as a distance between a center of an outermost one of the second servo readers and the center of the data element closest thereto. The symmetrical nature of the array and multiple servo readers on each side of the data elements enables use of narrower servo bands, which in turn allows more space on tape for data tracks, thereby increasing storage capacity per unit length of tape. Moreover, the symmetry enables use of the same design for both leading and trailing modules in a given magnetic head. In addition, a narrower servo band enable use of greater angles of the marks (e.g., magnetic bars) in the servo bands.

[0048] In one approach, which may be combined with other approaches describedherein, only two of the first servo readers and only two of the second servo readers are present in the array. The dual servo per servo band option provides two benefits: (1) itenables a higher angle of the servo band marks because the maximum time to cross a servoband is cut in half; and (2) it enables higher capacity because the required value for ^^^(described below) may be approximately half the value required for the single servo option.

[0049] In one approach, which may be combined with other approaches describedherein, a number of the data elements, ^^, in the array is 32, the data elements having an average pitch WEP.Head of the data elements is in a range of 86 to 97 microns. A center to center distance WSE.Short.Headbetween the data element closest to the first end of the array andthe first servo reader closest to the data elements is in a range of (WEP.Head / 2) + 3 to (WEP.Head / 2) + 10 microns. A center to center distance WSE.Long.Headbetween the data element closest to the first end of the array and the first servo reader farthest from the data elements is in a range of WEP.Head + 3 to WEP.Head + 10 microns. A center to center distance between the data element closest to the second end of the array and the second servo reader closest to the data element is about equal to WSE.Short.Head. A center to center distance between the data element closest to the second end of the array and the second servo reader farthest from thedata element is about equal to WSE.Long.Head. These dimensions have been found to maximizecapacity on the tape with minimal guard bands.

[0050] In one approach, which may be combined with other approaches describedherein, the data elements are write elements, wherein the magnetic head includes a second array aligned with the array in an intended direction of tape travel thereacross, the second array comprising read elements, at least two third servo readers positioned toward a first end of the second array and at least two fourth servo readers positioned toward a second end of the second array, wherein the second array is symmetrical about a centerpoint thereof, e.g., as if the array were folded over on the centerline such that the second end of the array overlies the first end of the array. This feature enables read-while-write, which is important for data integrity.

[0051] In one approach, which may be combined with other approaches describedherein, a longitudinal axis of the array is nominally tilted by greater than 0 degrees fromnormal relative to an intended direction of tape travel thereacross. The tilt provides a predefined “effective” element pitch, and enables compensation for tape lateral expansion and contraction by adjusting the tilt, which in turn increases or decreases the effective element pitch, enabling compensation for changes in tape and / or head dimensions due to moisture, thermal expansion and contraction, etc.

[0052] In one approach, which may be combined with other approaches describedherein, a second array of transducers is aligned along a longitudinal axis of the array. A firstend of the second array is positioned adjacent the array. The second array of transducers comprises second data elements and at least two third servo readers positioned toward a second end of the second array. The number of the second data elements is equal to thenumber of the data elements, A distance between the center of the innermost second servoreader and a center of the second data element of the second array closest thereto is the sameas the distance between the center of the outermost first servo reader and the center of the data element closest thereto. A distance between a center of the outermost second servoreader and a center of the second data element of the second array closest thereto is the same as the distance between the center of the innermost second servo reader and the center of thedata element closest thereto. An apparatus with such configuration, and as further describedherein, increases the capacity written on tape and also greatly increases the rate at which datacan be written or read, by operating on two data bands.

[0053] In a preferred approach, a combined array consisting of the array and the secondarray is symmetrical about a centerpoint of the combined array. Such symmetry provides similar benefits as noted above for approach having the symmetrical array.

[0054] In one approach, which may be combined with other approaches describedherein, an average pitch WEP.Head of the data elements satisfies one or more of the followingequations:^^^ − ^ ∙ ^^^^ ^^^^^^.^^^^~^^ ∙ ^^^ ∙ ^^^ (^^)with an accuracy of 10% (e.g., within a range of ± 10% of the value given by inserting theappropriate variables into the equation), where: WTapeis a total width of a magnetic tape specified by a format for which the apparatus is designed, WEdge is a width of an edge band of the magnetic tape specified by the format, NEis a total number of data elements in the array, NDBis a number of data bands on the magnetic tape specified by the format, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This pitch enables writing of more data tracks to the tape, increasing data storage capacity.

[0055] In one approach, which may be combined with other approaches describedherein, an average pitch WEP.Head of the data elements satisfies the following equation: ^^^.^^^^with an accuracy of 2% (e.g., within a range of ± 2% of the value given by inserting theappropriate variables into the equation), where:WTape is a total width of a magnetic tape specified by a format for which the apparatus is designed, WEdge is a width of an edge band of the magnetic tape specified by the format, WS is a width of a servo band of the magnetic tape specified by the format,WSBG is a width of a servo band guard of the magnetic tape specified by the format (e.g.,preferably WSBGis in a range of greater than 0 to 5 microns, more preferably less than about 4 microns, more preferably less than about 3.1 microns),WTP.Nom is a predefined nominal data track pitch that is preferably in a range of greater than 0to 650 nanometers,NE is a total number of data elements in the array for performing data operations on one databand, NDBis a number of data bands on the magnetic tape specified by the format, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This pitch enables writing of more data tracks to the tape, increasing data storage capacity.

[0056] In one approach, which may be combined with other approaches describedherein, the distance WSE.Short.Headbetween the center of the innermost first servo reader and the center of the data element closest thereto satisfies the following equation: ^^^ ^ ^^.^^^^ ^ ^^^^^.^^^^^.^^^^~ + + ^ ^^^^ (^^)with an accuracy of 2%, where: WEP.Head is an average pitch of the data elements of the array,WS is the width of the servo readers in the array,WSBGis a width of a servo band guard specified by a format for which the apparatus is designed, where WSBG is preferably in a range of greater than 0 to 5 microns, more preferably less than about 4 microns, more preferably less than about 3.1 microns, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This distance enables use of the dual servo per servo band option described elsewhere herein, which in turn enables use of narrower servo bands and higher storage per unit length of tape.

[0057] In one approach, which may be combined with other approaches describedherein, the distance WSE.Short.Headbetween the center of the innermost first servo reader and the center of the data element closest thereto satisfies the following equation:with an accuracy of 2%, where: WEP.Head is an average pitch of the data elements of the array,WS is the width of the servo readers in the array,WSBGis a width of a servo band guard specified by a format for which the apparatus is designed,WTP.Nom is a predefined nominal data track pitch that is preferably in a range of greater than 0to 650 nanometers, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This distance enables use of the dual servo per servo band option described elsewhere herein, which in turn enables use of narrower servo bands and higher storage per unit length of tape.

[0058] In one approach, which may be combined with other approaches describedherein, the distancebetween the center of the outermost first servo reader and the center of the data element closest thereto satisfies the following equation:with an accuracy of 2%, where: WEP.Headis an average pitch of the data elements of the array,WS is a width of the servo readers in the array (e.g., an average width of the servo readers, adesign width of each servo reader, etc.), WSBG is a width of a servo band guard specified by a format for which the apparatus is designed, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This distance enables use of the dual servo per servo band option described elsewhere herein, which in turn enables use of narrower servo bands and higher storage per unit length of tape.

[0059] In one approach, which may be combined with other approaches describedherein, the distancebetween the center of the outermost first servo reader and the center of the data element closest thereto satisfies the following equation:with an accuracy of 2%, where: WEP.Head is an average pitch of the data elements of the array,WS is a width of the servo readers in the array, WTP.Nomis a predefined nominal data track pitch that is preferably in a range of greater than 0 to 650 nanometers, WSBG is a width of a servo band guard specified by a format for which the apparatus is designed, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This distance enables use of the dual servo per servo band option described elsewhere herein, which in turn enables use of narrower servo bands and higher storage per unit length of tape.

[0060] In one approach, which may be combined with other approaches describedherein, a distance WServoSpan.Head between the center of the innermost one of the first servo readers and the center of the outermost one of the second servo readers satisfies the following equation:with an accuracy of 2%, where: NEis a total number of data elements in the array, WEP.Headis an average pitch of the data elements of the array,WS is a width of the servo readers in the array,WSBGis a width of a servo band guard specified by a format for which the apparatus isdesigned (e.g., in a range as set forth elsewhere herein), and^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This distance enables use of the dual servo per servo band option described elsewhere herein, which in turn enables use of narrower servo bands and higher storage per unit length of tape.

[0061] In one approach, which may be combined with other approaches describedherein, a distance WServoSpan.Head between the center of the innermost one of the first servo readers and the center of the outermost one of the second servo readers, e.g., as shown inFigures 15, 17, 18 and 19 labeled as ^^^^^, satisfies the following equation:with an accuracy of 2%, where: NE is a total number of data elements in the array, WEP.Headis an average pitch of the data elements of the array,WS is a width of the servo readers in the array,WTP.Nom is a predefined nominal data track pitch that is in a range of greater than 0 to 650nanometers,WSBG is a width of a servo band guard specified by the format wherein WSBG is in a range ofgreater than 0 to 5 microns, more preferably less than about 4 microns, more preferably less than about 3.1 microns, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head. This distance enables use of the dual servo per servo band option described elsewhere herein, which in turn enables use of narrower servo bands and higher storage per unit length of tape.

[0062] An apparatus, in accordance with one approach, includes a drive mechanism forpassing a magnetic tape over the magnetic head, and a controller electrically coupled to the magnetic head. Preferably, the controller is configured to not overwrite any portions of the servo bands with data tracks during writing.

[0063] An apparatus, in accordance with another general embodiment, includes amagnetic head having an array of transducers and a second array of transducers aligned along a longitudinal axis of the array, wherein a first end of the second array is positionedadjacent the array. The array comprises data elements, at least two first servo readerspositioned toward a first end of the array and at least two second servo readers positionedtoward a second end of the array. The second array includes second data elements and atleast two third servo readers positioned toward a second end of the second array. The array is symmetrical about a centerpoint thereof, such that a distance between a center of an innermost one of the first servo readers and a center of the data element closest thereto is the same as a distance between a center of an innermost one of the second servo readers and a center of the data element closest thereto, and such that a distance between a center of an outermost one of the first servo readers and the center of the data element closest thereto is the same as a distance between a center of an outermost one of the second servo readers and the center of the data element closest thereto. A distance between the center of the innermost second servo reader and a center of the data element of the second array closest thereto is the same as the distance between the center of the outermost first servo reader and the center ofthe data element closest thereto. A distance between a center of the outermost second servoreader and a center of the data element of the second array closest thereto is the same as the distance between the center of the innermost second servo reader and the center of the dataelement closest thereto. The symmetrical nature of the array and multiple servo readers oneach side of the data elements enables use of narrower servo bands, which in turn allows more space on tape for data tracks, thereby increasing storage capacity per unit length oftape. Moreover, the symmetry enables use of the same design for both leading and trailingmodules in a given magnetic head. In addition, a narrower servo band enable use of greater angles of the marks (e.g., magnetic bars) in the servo bands. Moreover, by spanning two data bands, an apparatus with such configuration, and as further described herein, increases the capacity written on tape and also greatly increases the rate at which data can be written or read, by operating on two data bands.

[0064] In a preferred approach, which may be combined with other approaches describedherein, only two of the first servo readers and only two of the second servo readers are present in the array. The dual servo per servo band option provides two benefits: (1) it enables a higher angle of the servo band marks because the maximum time to cross a servo band is cut in half; and (2) it enables higher capacity because the required value for ^^^(described below) may be approximately half the value required for the single servo option.

[0065] In one approach, which may be combined with other approaches describedherein, the data elements are write elements. The magnetic head includes a third arrayaligned with the array in an intended direction of tape travel thereacross and a fourth arrayaligned with the second array in the intended direction of tape travel. The third arrayincludes read elements, at least two fourth servo readers positioned toward a first end of thethird array and at least two fifth servo readers positioned toward a second end of the thirdarray. The third array is symmetrical about a centerpoint thereof. In addition, the combinedarray consisting of the third and fourth arrays may be symmetrical about the centerpoint ofthe combined array. This approach enables read-while-write, which is important for dataverification and integrity.

[0066] In one approach, which may be combined with other approaches describedherein, a longitudinal axis of the array is nominally tilted by greater than 0 degrees fromnormal relative to an intended direction of tape travel thereacross. The tilt provides a predefined “effective” element pitch, and enables compensation for tape lateral expansion and contraction by adjusting the tilt, which in turn increases or decreases the effectiveelement pitch, enabling compensation for changes in tape and / or head dimensions due tomoisture, thermal expansion and contraction, etc.

[0067] In one approach, which may be combined with other approaches describedherein, a combined array consisting of the array and the second array is symmetrical about acenterpoint of the combined array. Such symmetry provides similar benefits as noted above for approach having the symmetrical array.

[0068] A product, in accordance with one aspect of the present invention, includes amagnetic tape having a plurality of servo bands extending along a longitudinal axis of the magnetic tape. A width WSB.Tapeof each of the servo bands satisfies the following equation:to an accuracy of 10%, where: WEP.Tape is an average pitch of elements on the head used to read and write data and is given as.where: ^^is the number of elements used to write each data band, ^^^is the number of databands specified by a format of the magnetic tape, WEdgeis a width of an edge band of the magnetic tape where no data and no servo pattern is written as specified by the format, and WTape is a width of the magnetic tape. This product may be used with the new and novel apparatus designs noted above.

[0069] In one approach, which may be combined with other approaches describedherein, a pitch WServoSpan.Tape of adjacent pairs of the servo bands satisfies the following equation:to an accuracy of 1%, where: NEis a total number of data elements for concurrent writing per data band as specified by a format of the magnetic tape, WEP.Tape is an average pitch of data tracks specified by a format of the magnetic tape, and WSBG is a width of a servo band guard specified by the format, where WSBG is in a range of greater than 0 to 5 microns, more preferably less than about 4 microns, more preferably less than about 3.1 microns. This servo band pitch allows for writing more data tracks on tape relative to extant products.

[0070] In one approach, which may be combined with other approaches describedherein, a pitch WServoSpan.Tapeof adjacent pairs of the servo bands satisfies the following equation:with an accuracy of 1%, where: WEP.Tape is an average pitch of elements on the head used to read and write data and is given as:WSE.Short.Tapeis a design pitch, specified by a format of the magnetic tape, between a data element closest to a first end of an array and a servo reader of the array located closest to the data element, and is given by:WSE.Long.Tape is a design pitch, specified by a format of the magnetic tape, between the data element closest to the first end of the array and a second servo reader of the array located closest to the first end, and is given by: ^^^.^^^^^.^^^^~^^^.^^^^where: NEis a total number of data elements for concurrent writing specified by a format of the magnetic tape, and NDBis a total number of data bands on the tape specified by a format of the magnetic tape, and WTape is the width of the tape and specified by a format of the magnetic tape, and WEdge is the edge guard band of the tape and specified by a format of the magnetic tape as the region on the tape where no data or servo pattern is written. This servoband pitch allows for writing more data tracks on tape relative to extant products.

[0071] Various aspects of the present disclosure are described by narrative text,flowcharts, block diagrams of computer systems and / or block diagrams of the machine logic included in computer program product (CPP) embodiments. With respect to any flowcharts, depending upon the technology involved, the operations can be performed in a differentorder than what is shown in a given flowchart. For example, again depending upon the technology involved, two operations shown in successive flowchart blocks may be performed in reverse order, as a single integrated step, concurrently, or in a manner at least partially overlapping in time.

[0072] A computer program product embodiment ("CPP embodiment" or “CPP”) is aterm used in the present disclosure to describe any set of one, or more, storage media (also called "mediums") collectively included in a set of one, or more, storage devices that collectively include machine readable code corresponding to instructions and / or data for performing computer operations specified in a given CPP claim. A "storage device" is any tangible device that can retain and store instructions for use by a computer processor. Without limitation, the computer readable storage medium may be an electronic storage medium, a magnetic storage medium, an optical storage medium, an electromagnetic storagemedium, a semiconductor storage medium, a mechanical storage medium, or any suitablecombination of the foregoing. Some known types of storage devices that include these mediums include: diskette, hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or Flash memory), static random access memory (SRAM), compact disc read-only memory (CD-ROM), digital versatile disk (DVD), memory stick, floppy disk, mechanically encoded device (such as punch cards or pits / lands formed in a major surface of a disc) or any suitable combination of the foregoing. A computer readable storage medium, as that term is used in the present disclosure, is not to be construed as storage in the form of transitory signals per se, such as radio waves or other freely propagating electromagnetic waves, electromagnetic waves propagating through a waveguide, light pulses passing through a fiber optic cable, electrical signals communicated through a wire, and / or other transmission media. As will be understood by those of skill in the art, data is typically moved at some occasional points in time during normal operations of a storage device, such as during access, de-fragmentation or garbage collection, but this does not render the storage device as transitory because the data is not transitory while it is stored.

[0073] Computing environment 100 contains an example of an environment for theexecution of at least some of the computer code involved in performing the inventive methods, such as code in block 200 for operating on a magnetic tape. In addition to block 200, computing environment 100 includes, for example, computer 101, wide area network (WAN) 102, end user device (EUD) 103, remote server 104, public cloud 105, and private cloud 106. In this embodiment, computer 101 includes processor set 110 (includingprocessing circuitry 120 and cache 121), communication fabric 111, volatile memory 112, persistent storage 113 (including operating system 122 and block 200, as identified above), peripheral device set 114 (including user interface (UI) device set 123, storage 124, and Internet of Things (IoT) sensor set 125), and network module 115. Remote server 104 includes remote database 130. Public cloud 105 includes gateway 140, cloud orchestrationmodule 141, host physical machine set 142, virtual machine set 143, and container set 144.

[0074] COMPUTER 101 may take the form of a desktop computer, laptop computer,tablet computer, smart phone, smart watch or other wearable computer, mainframe computer, quantum computer or any other form of computer or mobile device now known orto be developed in the future that is capable of running a program, accessing a network orquerying a database, such as remote database 130. As is well understood in the art of computer technology, and depending upon the technology, performance of a computer- implemented method may be distributed among multiple computers and / or between multiple locations. On the other hand, in this presentation of computing environment 100, detailed discussion is focused on a single computer, specifically computer 101, to keep the presentation as simple as possible. Computer 101 may be located in a cloud, even though itis not shown in a cloud in FIG. 1. On the other hand, computer 101 is not required to be in acloud except to any extent as may be affirmatively indicated.

[0075] PROCESSOR SET 110 includes one, or more, computer processors of any typenow known or to be developed in the future. Processing circuitry 120 may be distributed over multiple packages, for example, multiple, coordinated integrated circuit chips. Processing circuitry 120 may implement multiple processor threads and / or multiple processor cores. Cache 121 is memory that is located in the processor chip package(s) and istypically used for data or code that should be available for rapid access by the threads orcores running on processor set 110. Cache memories are typically organized into multiple levels depending upon relative proximity to the processing circuitry. Alternatively, some, or all, of the cache for the processor set may be located “off chip.” In some computing environments, processor set 110 may be designed for working with qubits and performing quantum computing.

[0076] Computer readable program instructions are typically loaded onto computer 101to cause a series of operational steps to be performed by processor set 110 of computer 101 and thereby effect a computer-implemented method, such that the instructions thus executed will instantiate the methods specified in flowcharts and / or narrative descriptions of computer-implemented methods included in this document (collectively referred to as “theinventive methods”). These computer readable program instructions are stored in various types of computer readable storage media, such as cache 121 and the other storage mediadiscussed below. The program instructions, and associated data, are accessed by processorset 110 to control and direct performance of the inventive methods. In computing environment 100, at least some of the instructions for performing the inventive methods may be stored in block 200 in persistent storage 113.

[0077] COMMUNICATION FABRIC 111 is the signal conduction path that allows thevarious components of computer 101 to communicate with each other. Typically, this fabric is made of switches and electrically conductive paths, such as the switches and electrically conductive paths that make up buses, bridges, physical input / output ports and the like. Other types of signal communication paths may be used, such as fiber optic communication paths and / or wireless communication paths.

[0078] VOLATILE MEMORY 112 is any type of volatile memory now known or to bedeveloped in the future. Examples include dynamic type random access memory (RAM) or static type RAM. Typically, volatile memory 112 is characterized by random access, but this is not required unless affirmatively indicated. In computer 101, the volatile memory 112 is located in a single package and is internal to computer 101, but, alternatively or additionally, the volatile memory may be distributed over multiple packages and / or located externally with respect to computer 101.

[0079] PERSISTENT STORAGE 113 is any form of non-volatile storage for computersthat is now known or to be developed in the future. The non-volatility of this storage means that the stored data is maintained regardless of whether power is being supplied to computer 101 and / or directly to persistent storage 113. Persistent storage 113 may be a read only memory (ROM), but typically at least a portion of the persistent storage allows writing of data, deletion of data and re-writing of data. Some familiar forms of persistent storage include magnetic disks and solid state storage devices. Operating system 122 may take several forms, such as various known proprietary operating systems or open source Portable Operating System Interface-type operating systems that employ a kernel. The code included in block 200 typically includes at least some of the computer code involved in performing the inventive methods.

[0080] PERIPHERAL DEVICE SET 114 includes the set of peripheral devices ofcomputer 101. Data communication connections between the peripheral devices and the other components of computer 101 may be implemented in various ways, such as Bluetooth connections, Near-Field Communication (NFC) connections, connections made by cables(such as universal serial bus (USB) type cables), insertion-type connections (for example, secure digital (SD) card), connections made through local area communication networks and even connections made through wide area networks such as the internet. In various embodiments, UI device set 123 may include components such as a display screen, speaker, microphone, wearable devices (such as goggles and smart watches), keyboard, mouse, printer, touchpad, game controllers, and haptic devices. Storage 124 is external storage, such as an external hard drive, or insertable storage, such as an SD card. Storage 124 may be persistent and / or volatile. In some embodiments, storage 124 may take the form of aquantum computing storage device for storing data in the form of qubits. In embodimentswhere computer 101 is required to have a large amount of storage (for example, where computer 101 locally stores and manages a large database) then this storage may be provided by peripheral storage devices designed for storing very large amounts of data, such as a storage area network (SAN) that is shared by multiple, geographically distributed computers. IoT sensor set 125 is made up of sensors that can be used in Internet of Things applications. For example, one sensor may be a thermometer and another sensor may be a motion detector.

[0081] NETWORK MODULE 115 is the collection of computer software, hardware,and firmware that allows computer 101 to communicate with other computers through WAN 102. Network module 115 may include hardware, such as modems or Wi-Fi signal transceivers, software for packetizing and / or de-packetizing data for communication network transmission, and / or web browser software for communicating data over the internet. In some embodiments, network control functions and network forwarding functions of network module 115 are performed on the same physical hardware device. In other embodiments (for example, embodiments that utilize software-defined networking (SDN)), the control functions and the forwarding functions of network module 115 are performed on physically separate devices, such that the control functions manage several different network hardware devices. Computer readable program instructions for performing the inventive methods can typically be downloaded to computer 101 from an external computer or external storage device through a network adapter card or network interface included in network module 115.

[0082] WAN 102 is any wide area network (for example, the internet) capable ofcommunicating computer data over non-local distances by any technology for communicating computer data, now known or to be developed in the future. In some embodiments, the WAN 102 may be replaced and / or supplemented by local area networks (LANs) designed to communicate data between devices located in a local area, such as a Wi-Fi network. The WAN and / or LANs typically include computer hardware such as copper transmission cables, optical transmission fibers, wireless transmission, routers, firewalls, switches, gateway computers and edge servers.

[0083] END USER DEVICE (EUD) 103 is any computer system that is used andcontrolled by an end user (for example, a customer of an enterprise that operates computer 101), and may take any of the forms discussed above in connection with computer 101. EUD 103 typically receives helpful and useful data from the operations of computer 101. For example, in a hypothetical case where computer 101 is designed to provide a recommendation to an end user, this recommendation would typically be communicated from network module 115 of computer 101 through WAN 102 to EUD 103. In this way, EUD 103 can display, or otherwise present, the recommendation to an end user. In some embodiments, EUD 103 may be a client device, such as thin client, heavy client, mainframe computer, desktop computer and so on.

[0084] REMOTE SERVER 104 is any computer system that serves at least some dataand / or functionality to computer 101. Remote server 104 may be controlled and used by the same entity that operates computer 101. Remote server 104 represents the machine(s) that collect and store helpful and useful data for use by other computers, such as computer 101. For example, in a hypothetical case where computer 101 is designed and programmed to provide a recommendation based on historical data, then this historical data may be provided to computer 101 from remote database 130 of remote server 104.

[0085] PUBLIC CLOUD 105 is any computer system available for use by multipleentities that provides on-demand availability of computer system resources and / or other computer capabilities, especially data storage (cloud storage) and computing power, withoutdirect active management by the user. Cloud computing typically leverages sharing ofresources to achieve coherence and economies of scale. The direct and active management of the computing resources of public cloud 105 is performed by the computer hardware and / or software of cloud orchestration module 141. The computing resources provided by public cloud 105 are typically implemented by virtual computing environments that run onvarious computers making up the computers of host physical machine set 142, which is theuniverse of physical computers in and / or available to public cloud 105. The virtual computing environments (VCEs) typically take the form of virtual machines from virtual machine set 143 and / or containers from container set 144. It is understood that these VCEs may be stored as images and may be transferred among and between the various physical machine hosts, either as images or after instantiation of the VCE. Cloud orchestrationmodule 141 manages the transfer and storage of images, deploys new instantiations of VCEs and manages active instantiations of VCE deployments. Gateway 140 is the collection of computer software, hardware, and firmware that allows public cloud 105 to communicate through WAN 102.

[0086] Some further explanation of virtualized computing environments (VCEs) willnow be provided. VCEs can be stored as “images.” A new active instance of the VCE can be instantiated from the image. Two familiar types of VCEs are virtual machines and containers. A container is a VCE that uses operating-system-level virtualization. This refers to an operating system feature in which the kernel allows the existence of multiple isolated user-space instances, called containers. These isolated user-space instances typically behave as real computers from the point of view of programs running in them. A computer program running on an ordinary operating system can utilize all resources of that computer, such as connected devices, files and folders, network shares, CPU power, and quantifiable hardware capabilities. However, programs running inside a container can only use the contents of the container and devices assigned to the container, a feature which is known as containerization.

[0087] PRIVATE CLOUD 106 is similar to public cloud 105, except that the computingresources are only available for use by a single enterprise. While private cloud 106 is depicted as being in communication with WAN 102, in other embodiments a private cloud may be disconnected from the internet entirely and only accessible through a local / private network. A hybrid cloud is a composition of multiple clouds of different types (for example,private, community or public cloud types), often respectively implemented by differentvendors. Each of the multiple clouds remains a separate and discrete entity, but the larger hybrid cloud architecture is bound together by standardized or proprietary technology that enables orchestration, management, and / or data / application portability between the multiple constituent clouds. In this embodiment, public cloud 105 and private cloud 106 are both part of a larger hybrid cloud.

[0088] In some aspects, a system according to various approaches may include aprocessor and logic integrated with and / or executable by the processor, the logic being configured to perform one or more of the process steps recited herein. The processor may be of any configuration as described herein, such as a discrete processor or a processing circuit that includes many components such as processing hardware, memory, I / O interfaces, etc. By integrated with, what is meant is that the processor has logic embedded therewith as hardware logic, such as an application specific integrated circuit (ASIC), a FPGA, etc. Byexecutable by the processor, what is meant is that the logic is hardware logic; software logic such as firmware, part of an operating system, part of an application program; etc., or somecombination of hardware and software logic that is accessible by the processor andconfigured to cause the processor to perform some functionality upon execution by the processor. Software logic may be stored on local and / or remote memory of any memory type, as known in the art. Any processor known in the art may be used, such as a software processor module and / or a hardware processor such as an ASIC, a FPGA, a central processing unit (CPU), an integrated circuit (IC), a graphics processing unit (GPU), etc.

[0089] FIG. 2A illustrates a simplified tape drive 201 of a tape-based data storagesystem, which may be employed in the context of the present invention. While one specificimplementation of a tape drive is shown in FIG.2A, it should be noted that the embodiments described herein may be implemented in the context of any type of tape drive system.

[0090] As shown, a tape supply cartridge 203 and a take-up reel 205 are provided tosupport a tape 207. One or more of the reels may form part of a removable cartridge and arenot necessarily part of the tape drive 201. The tape drive, such as that illustrated in FIG. 2A,may further include drive motor(s) to drive the tape supply cartridge 203 and the take-up reel205 to move the tape 207 over a tape head 211 of any type. Such head may include an arrayof read elements (also referred to as readers, reader elements, and read transducers), writeelements (also known in the art as writers, writer elements, and write transducers), or both.

[0091] Guides 213 guide the tape 207 across the tape head 211. Such tape head 211 is inturn coupled to a controller 215 via a cable 217. The controller 215, may be or include aprocessor and / or any logic for controlling any subsystem of the drive 201. For example, thecontroller 215 typically controls head functions such as servo following, data writing, datareading, etc. The controller 215 may include at least one servo channel and at least one datachannel, each of which include data flow processing logic configured to process and / or storeinformation to be written to and / or read from the tape 207. The controller 215 may operateunder logic known in the art, as well as any logic disclosed herein, and thus may be considered as a processor for any of the descriptions of tape drives included herein, invarious approaches. The controller 215 may be coupled to a memory 219 of any known type,which may store instructions executable by the controller 215. Moreover, the controller 215 may be configured and / or programmable to perform or control some or all of themethodologies presented herein. Thus, the controller 215 may be considered to beconfigured to perform various operations by way of logic programmed into one or morechips, modules, and / or blocks; software, firmware, and / or other instructions being availableto one or more processors; etc., and combinations thereof.

[0092] The cable 217 may include read / write circuits to transmit data to the tape head211 to be recorded on the tape 207 and to receive data read by the tape head 211 from thetape 207. An actuator 221 controls position of the tape head 211 relative to the tape 207.

[0093] An interface 223 may also be provided for communication between the tape drive201 and a host (internal or external) to send and receive the data and for controlling theoperation of the tape drive 201 and communicating the status of the tape drive 201 to thehost, all as will be understood by those of skill in the art.

[0094] FIG. 2B illustrates an exemplary tape cartridge 231, according to one aspect ofthe present invention. Such tape cartridge 231 may be used with a system such as that shownin FIG. 2A. As shown, the tape cartridge 231 includes a housing 233, a tape 207 in thehousing 233, and a nonvolatile memory 237 coupled to the housing 233. In someapproaches, the nonvolatile memory 237 may be embedded inside the housing 233, as shownin FIG. 2B. In more approaches, the nonvolatile memory 237 may be attached to the insideor outside of the housing 233 without modification of the housing 233. For example, thenonvolatile memory may be embedded in a self-adhesive label 235. In one preferredapproach, the nonvolatile memory 237 may be a Flash memory device, read-only memory(ROM) device, etc., embedded into or coupled to the inside or outside of the tape cartridge231. The nonvolatile memory is accessible by the tape drive and the tape operating software(the driver software), and / or another device.

[0095] By way of example, FIG. 2C illustrates a side view of a flat-lapped, bi-directional, two-module magnetic tape head 211 which may be implemented in the contextof the present invention. As shown, the head includes a pair of bases 202, each equippedwith a module 204, and fixed at a small angle α with respect to each other. The bases may be “U-beams” that are adhesively coupled together. Each module 204 includes a substrate 204A and a closure 204B with a thin film portion, commonly referred to as a “gap” in which theread elements and / or write elements 206 are formed. In use, a tape 208 is moved over themodules 204 along a media (tape) bearing surface 209 in the manner shown for reading andwriting data on the tape 208 using the read elements and write elements. The wrap angle θ ofthe tape 208 at edges going onto and exiting the flat media support surfaces 209 are usuallybetween about 0.1 degree and about 3 degrees.

[0096] The substrates 204A are typically constructed of a wear resistant material, such asa ceramic. The closures 204B may be made of the same or similar ceramic as the substrates 204A.

[0097] Cables 217 are provided for enabling communication between the controller andthe elements 206 of each of the modules 204. Pads on a cable 217 are typically wire bondedto pads on the associated module 204.

[0098] The read elements and write elements may be arranged in a piggyback or mergedconfiguration. An illustrative piggybacked configuration comprises a (magneticallyinductive) write element on top of (or below) a (magnetically shielded) read element (e.g., amagnetoresistive reader, etc.), wherein the poles of the write element and the shields of theread element are generally separated. An illustrative merged configuration comprises onereader shield in the same physical layer as one writer pole (hence, "merged"). The readelements and write elements may also be arranged in an interleaved configuration.Alternatively, each array of channels may be read elements or write elements only. Any ofthese arrays may contain one or more servo readers for reading servo data on the medium.

[0099] FIG. 2D illustrates the tape bearing surface 209 of one of the modules 204 takenfrom Line 2D of FIG. 2C. A representative tape 208 is shown in dashed lines. The module204 is preferably long enough to be able to support the tape as the head steps between data bands.

[0100] In this example, the tape 208 includes 4 to 32 data bands, e.g., with 16 data bandsand 17 servo tracks 210, as shown in FIG. 2D on a one-half inch wide tape 208. The databands are defined between servo tracks 210. Each data band may include a number of datatracks, for example 1024 data tracks (not shown). During read / write operations, the readelements and / or write elements 206 are positioned to specific track positions within one ofthe data bands. Outer readers, sometimes called servo readers, read the servo tracks 210. Theservo signals are in turn used in a conventional manner to keep the read elements and / orwrite elements 206 aligned with a particular set of tracks during the read / write operations.

[0101] FIG. 2E depicts a plurality of read elements and / or write elements 206 formed ina gap 218 on the module 204 in Circle 2E of FIG. 2D. As shown in FIG. 2E, the array ofread elements and write elements 206 includes, for example, 16 write elements 214, 16 readelements 216 and two servo readers 212, though the number of elements may vary.Illustrative approaches include 8, 16, 32, 40, and 64 active read elements and / or writeelements 206 per array, and alternatively interleaved designs having odd numbers of readelements or write elements such as 17, 25, 33, etc. An illustrative approach includes 32 readelements per array and / or 32 write elements per array, where the actual number of elementelements could be greater, e.g., 33, 34, etc. Multiple simultaneously-operated elements allowthe tape to travel at a modest velocity while maintaining a high data transfer rate. Lower velocities are desirable to reduce mechanical difficulties from speed-induced tracking.

[0102] While the read elements and write elements may be arranged in a piggybackconfiguration as shown in FIG. 2E, the read elements 216 and write elements 214 may alsobe arranged in an interleaved configuration. Alternatively, each array of read elements and / orwrite elements 206 may be read elements or write elements only, and the arrays may containone or more servo readers 212. As noted by considering FIGS. 2C and 2D-2E together, eachmodule 204 may include a complementary set of read elements and / or write elements 206for such things as bi-directional reading and writing, read-while-write capability, backward compatibility, etc.

[0103] FIG. 2F shows a partial tape bearing surface view of complementary modules ofa magnetic tape head 211, according to one approach. In this approach, each module has aplurality of read / write (R / W) pairs in a piggyback configuration formed on a commonsubstrate 204A and an optional electrically insulative insulating layer 236. The writeelements 214 and the read elements 216 are aligned parallel to an intended direction of travelof a tape medium thereacross to form an R / W pair, exemplified by R / W pairs 222. Note thatthe intended direction of tape travel is sometimes referred to herein as the direction of tape travel, and such terms may be used interchangeably. Such direction of tape travel may be inferred from the design of the system, e.g., by examining the guides; observing the actual direction of tape travel relative to the reference point; etc. Moreover, in a system operable for bi-direction reading and / or writing, the direction of tape travel in both directions is typically parallel and thus both directions may be considered equivalent to each other.

[0104] Several R / W pairs 222 may be present, such as 8, 16, 32 pairs, etc. The R / W pairs222 as shown are linearly aligned in a direction generally perpendicular to a direction of tapetravel thereacross. However, the pairs may also be aligned diagonally, etc. Servo readers 212 are positioned on the outside of the array of R / W pairs, the function of which is well known.

[0105] Generally, the magnetic tape medium moves in either a forward or reversedirection as indicated by arrow 220. The magnetic tape medium and head assembly 211 operate in a transducing relationship in the manner well-known in the art. The head assembly211 includes two thin-film modules 224 and 226 of generally identical construction.

[0106] Modules 224 and 226 are joined together with a space present between closures204B thereof (partially shown) to form a single physical unit to provide read-while-writecapability by activating the write element of the leading module and read element of thetrailing module aligned with the write element of the leading module parallel to the directionof tape travel relative thereto. When a module 224, 226 of a magnetic tape head 211 isconstructed, layers are formed in the gap 218 created above an electrically conductivesubstrate 204A (partially shown), e.g., of AlTiC, in generally the following order for theR / W pairs 222: an insulating layer 236, a first shield 232 typically of an iron alloy such asNiFe (e.g., ~80 / 20 at% NiFe, also known as permalloy), cobalt zirconium tantalum (CZT) orAl-Fe-Si (Sendust), a sensor 234 for sensing a data track on a magnetic medium, a secondshield 238 typically of a nickel-iron alloy (e.g., permalloy), first and second writer poles 228,230, and a coil (not shown). The sensor may be of any known type, including those based onmagnetoresistive (MR), GMR, AMR, tunneling magnetoresistance (TMR), etc.

[0107] The first and second writer poles 228, 230 may be fabricated from high magneticmoment materials such as CoFe. Note that these materials are provided by way of example only, and other materials may be used. Additional layers such as insulation between the shields and / or pole tips and an insulation layer surrounding the sensor may be present. Illustrative materials for the insulation include alumina and other oxides, insulative polymers, etc.

[0108] The configuration of the tape head 211, according to one approach, includesmultiple modules, preferably three or more. In a write-read-write (W-R-W) head, outermodules for writing flank one or more inner modules for reading. Referring to FIG.3,depicting a W-R-W configuration, the outer modules 252, 256 each include one or morearrays of write elements 260. The inner module 254 of FIG. 3 includes one or more arrays ofread elements 258 in a similar configuration. Variations of a multi-module head include a R-W-R head (FIG. 4), a R-R-W head, a W-W-R head, etc. In yet other variations, one or moreof the modules may have read / write pairs of elements. Moreover, more than three modulesmay be present. In further approaches, two outer modules may flank two or more innermodules, e.g., in a W-R-R-W, a R-W-W-R arrangement, etc. For simplicity, a W-R-W head is used primarily herein to exemplify approaches of the present invention. One skilled in the art apprised with the teachings herein will appreciate how permutations of the present invention would apply to configurations other than a W-R-W configuration.

[0109] FIG. 5 illustrates a magnetic head 211 according to one aspect of the presentinvention that includes first, second and third modules 302, 304, 306 each having a tape bearing surface 308, 310, 312 respectively, which may be flat, contoured, etc. Note that while the term “tape bearing surface” appears to imply that the surface facing the tape 315 isin physical contact with the tape bearing surface, this is not necessarily the case. Rather, onlya portion of the tape may be in contact with the tape bearing surface, constantly orintermittently, with other portions of the tape riding (or “flying”) above the tape bearingsurface on a layer of air, sometimes referred to as an “air bearing”. The first module 302 will be referred to as the “leading” module as it is the first module encountered by the tape in athree module design for tape moving in the indicated direction. The third module 306 will bereferred to as the “trailing” module. The trailing module follows the middle module and is the last module seen by the tape in a three module design. The leading and trailing modules 302, 306 are referred to collectively as outer modules. Also note that the outer modules 302, 306 will alternate as leading modules, depending on the direction of travel of the tape 315.

[0110] In one approach, the tape bearing surfaces 308, 310, 312 of the first, second andthird modules 302, 304, 306 lie on about parallel planes (which is meant to include parallel and nearly parallel planes, e.g., between parallel and tangential as in FIG.6), and the tape bearing surface 310 of the second module 304 is above the tape bearing surfaces 308, 312 of the first and third modules 302, 306. As described below, this has the effect of creating the desired wrap angle α2 of the tape relative to the tape bearing surface 310 of the second module 304.

[0111] Where the tape bearing surfaces 308, 310, 312 lie along parallel or nearly parallelyet offset planes, intuitively, the tape should peel off of the tape bearing surface 308 of theleading module 302. However, the vacuum created by a skiving edge 318 of the leadingmodule 302 has been found by experimentation to be sufficient to keep the tape adhered tothe tape bearing surface 308 of the leading module 302. A trailing edge 320 of the leadingmodule 302 (the end from which the tape leaves the leading module 302) is the approximate reference point which defines the wrap angle α2 over the tape bearing surface 310 of the second module 304. The tape stays in close proximity to the tape bearing surface until closeto the trailing edge 320 of the leading module 302. Accordingly, elements 322 may belocated near the trailing edges of the outer modules 302, 306. These approaches are particularly adapted for write-read-write applications.

[0112] A benefit of this and other approaches described herein is that, because the outermodules 302, 306 are fixed at a determined offset from the second module 304, the inner wrap angle α2 is fixed when the modules 302, 304, 306 are coupled together or are otherwise fixed into a head. The inner wrap angle α2is approximately tan-1(δ / W) where δ is the height difference between the planes of the tape bearing surfaces 308, 310 and W is the width between the opposing ends of the tape bearing surfaces 308, 310. An illustrative inner wrapangle α2 is in a range of about 0.3° to about 1.1°, though can be any angle required by the design.

[0113] Beneficially, the inner wrap angle α2 on the side of the module 304 receiving thetape (leading edge) will be larger than the inner wrap angle α3 on the trailing edge, as thetape 315 rides above the trailing module 306. This difference is generally beneficial as a smaller α3tends to oppose what has heretofore been a steeper exiting effective wrap angle.

[0114] Note that the tape bearing surfaces 308, 312 of the outer modules 302, 306 arepositioned to achieve a negative wrap angle at the trailing edge 320 of the leading module302. This is generally beneficial in helping to reduce friction due to contact with the trailing edge 320, provided that proper consideration is given to the location of the crowbar regionthat forms in the tape where it peels off the head. This negative wrap angle also reducesflutter and scrubbing damage to the elements on the leading module 302. Further, at the trailing module 306, the tape 315 flies over the tape bearing surface 312 so there is virtuallyno wear on the elements when tape is moving in this direction. Particularly, the tape 315entrains air and so will not significantly ride on the tape bearing surface 312 of the third module 306 (some contact may occur). This is permissible, because the leading module 302 is writing while the trailing module 306 is idle.

[0115] Writing and reading functions are performed by different modules at any giventime. In one approach, the second module 304 includes a plurality of data and optional servo readers 331 and no write elements. The first and third modules 302, 306 include a plurality of write elements 322 and no data read elements, with the exception that the outer modules 302, 306 may include optional servo readers. The servo readers may be used to position the head during reading and / or writing operations. The servo reader(s) on each module are typically located towards the end of the array of read elements or write elements.

[0116] By having only read elements or side by side write elements and servo readers inthe gap between the substrate and closure, the gap length can be substantially reduced. Typical heads have piggybacked read elements and write elements, where the write element is formed above each read element. A typical gap is 20-35 microns. However, irregularities on the tape may tend to droop into the gap and create gap erosion. Thus, the smaller the gap the better. The smaller gap enabled herein exhibits fewer wear related problems.

[0117] In some approaches, the second module 304 has a closure, while the first andthird modules 302, 306 do not have a closure. Where there is no closure, preferably a hard coating is added to the module. One preferred coating is diamond-like carbon (DLC).

[0118] In the approach shown in FIG. 5, the first, second, and third modules 302, 304,306 each have a closure 332, 334, 336, which extends the tape bearing surface of the associated module, thereby effectively positioning the read / write elements away from theedge of the tape bearing surface. The closure 332 on the second module 304 can be aceramic closure of a type typically found on tape heads. The closures 334, 336 of the firstand third modules 302, 306, however, may be shorter than the closure 332 of the secondmodule 304 as measured parallel to a direction of tape travel over the respective module.This enables positioning the modules closer together. One way to produce shorter closures334, 336 is to lap the standard ceramic closures of the second module 304 an additional amount. Another way is to plate or deposit thin film closures above the elements during thin film processing. For example, a thin film closure of a hard material such as Sendust or nickel-iron alloy (e.g., 45 / 55) can be formed on the module.

[0119] With reduced-thickness ceramic or thin film closures 334, 336 or no closures onthe outer modules 302, 306, the write-to-read gap spacing can be reduced to less than about1 mm, e.g., about 0.75 mm, or 50% less than commonly-used linear tape open (LTO) tapehead spacing. The open space between the modules 302, 304, 306 can still be set toapproximately 0.5 to 0.6 mm, which in some approaches is ideal for stabilizing tape motionover the second module 304.

[0120] Depending on tape tension and stiffness, it may be desirable to angle the tapebearing surfaces of the outer modules relative to the tape bearing surface of the secondmodule. FIG. 6 illustrates an approach where the modules 302, 304, 306 are in a tangent ornearly tangent (angled) configuration. Particularly, the tape bearing surfaces of the outer modules 302, 306 are about parallel to the tape at the desired wrap angle α2 of the second module 304. In other words, the planes of the tape bearing surfaces 308, 312 of the outer modules 302, 306 are oriented at about the desired wrap angle α2of the tape 315 relative to the second module 304. The tape will also pop off of the trailing module 306 in this approach, thereby reducing wear on the elements in the trailing module 306. These approaches are particularly useful for write-read-write applications. Additional aspects ofthese approaches are similar to those given above.

[0121] Typically, the tape wrap angles may be set about midway between the approachesshown in FIGS. 5 and 6.

[0122] FIG. 7 illustrates an approach where the modules 302, 304, 306 are in anoverwrap configuration. Particularly, the tape bearing surfaces 308, 312 of the outer modules 302, 306 are angled slightly more than the tape 315 when set at the desired wrap angle α2relative to the second module 304. In this approach, the tape does not pop off of the trailing module, allowing it to be used for writing or reading. Accordingly, the leading and middle modules can both perform reading and / or writing functions while the trailing module canread any just-written data. Thus, these approaches are preferred for write-read-write, read-write-read, and write-write-read applications. In the latter approaches, closures should be wider than the tape canopies for ensuring read capability. The wider closures may require awider gap-to-gap separation. Therefore, a preferred approach has a write-read-writeconfiguration, which may use shortened closures that thus allow closer gap-to-gap separation.

[0123] Additional aspects of the approaches shown in FIGS. 6 and 7 are similar to thosegiven above.

[0124] A 32 channel version of a multi-module tape head 211 may use cables 350having leads on the same or smaller pitch as current 16 channel piggyback LTO modules, or alternatively the connections on the module may be organ-keyboarded for a 50% reductionin cable span. Over-under, writing pair unshielded cables may be used for the writeelements, which may have integrated servo readers.

[0125] The outer wrap angles α1 may be set in the drive, such as by guides of any typeknown in the art, such as adjustable rollers, slides, etc. or alternatively by outriggers, which are integral to the head. For example, rollers having an offset axis may be used to set the wrap angles. The offset axis creates an orbital arc of rotation, allowing precise alignment of the wrap angle α1.

[0126] To assemble any of the approaches described above, conventional u-beamassembly can be used. Accordingly, the mass of the resultant head may be maintained oreven reduced relative to heads of previous generations. In other approaches, the modules may be constructed as a unitary body. Those skilled in the art, armed with the present teachings, will appreciate that other known methods of manufacturing such heads may be adapted for use in constructing such heads. Moreover, unless otherwise specified, processesand materials of types known in the art may be adapted for use in various approaches inconformance with the teachings herein, as would become apparent to one skilled in the art upon reading the present disclosure.

[0127] As a tape is run over a module, it is preferred that the tape passes sufficientlyclose to magnetic elements on the module such that reading and / or writing is efficiently performed, e.g., with a low error rate. According to some approaches, tape tenting may be used to ensure the tape passes sufficiently close to the portion of the module having themagnetic transducers. To better understand this process, FIGS.8A-8C illustrate the principles of tape tenting. FIG.8A shows a module 800 having an upper tape bearing surface 802 extending between opposite edges 804, 806. A stationary tape 808 is shown wrapping around the edges 804, 806. As shown, the bending stiffness of the tape 808 lifts the tape off of the tape bearing surface 802. Tape tension tends to flatten the tape profile, as shown in FIG.8A. Where tape tension is minimal, the curvature of the tape is more parabolic than shown.

[0128] FIG. 8B depicts the tape 808 in motion. The leading edge, i.e., the first edge thetape encounters when moving, may serve to skive air from the tape, thereby creating a subambient air pressure between the tape 808 and the tape bearing surface 802. In FIG.8B, the leading edge is the left edge and the right edge is the trailing edge when the tape is moving left to right. As a result, atmospheric pressure above the tape urges the tape toward the tape bearing surface 802, thereby creating tape tenting proximate each of the edges. The tape bending stiffness resists the effect of the atmospheric pressure, thereby causing the tape tenting proximate both the leading and trailing edges. Modeling predicts that the two tents are very similar in shape.

[0129] FIG. 8C depicts how the subambient pressure urges the tape 808 toward the tapebearing surface 802 even when a trailing guide 810 is positioned above the plane of the tape bearing surface.

[0130] It follows that tape tenting may be used to direct the path of a tape as it passesover a module. As previously mentioned, tape tenting may be used to ensure the tape passes sufficiently close to the portion of the module having the magnetic transducers, preferably such that reading and / or writing is efficiently performed, e.g., with a low error rate.

[0131] Magnetic tapes (also referred to as tapes, magnetic recording tapes, tape media,and the like) may be stored in tape cartridges that are, in turn, stored at storage slots or thelike inside a data storage library. The tape cartridges may be stored in the library such that they are accessible for physical retrieval. In addition to magnetic tapes and tape cartridges, data storage libraries may include data storage drives that store data to, and / or retrieve data from, the magnetic tapes. Moreover, tape libraries and the components included therein may implement a file system which enables access to tape and data stored on the tape.

[0132] File systems may be used to control how data is stored in, and retrieved from,memory. Thus, a file system may include the processes and data structures that an operating system uses to keep track of files in memory, e.g., the way the files are organized inmemory. Linear Tape File System (LTFS) is an exemplary format of a file system that maybe implemented in a given library in order to enable access to compliant tapes. It should beappreciated that various approaches herein can be implemented with a wide range of filesystem formats, including for example IBM® Spectrum® Archive Library Edition (LTFSLE) (IBM and all IBM–based trademarks and logos are trademarks or registered trademarksof International Business Machines Corporation and / or its affiliates). However, to provide acontext, and solely to assist the reader, some of the approaches below may be described withreference to LTFS, which is a type of file system format. This has been done by way ofexample only, and should not be deemed limiting on the invention defined in the claims.

[0133] A tape cartridge may be “loaded” by inserting the cartridge into the tape drive,and the tape cartridge may be “unloaded” by removing the tape cartridge from the tape drive. Once loaded in a tape drive, the tape in the cartridge may be “threaded” through the drive by physically pulling the tape (the magnetic recording portion) from the tape cartridge, and passing it above a magnetic head of a tape drive. Furthermore, the tape may be attached on atake-up reel (e.g., see 205 of FIG. 2A above) to move the tape over the magnetic head.

[0134] Once threaded in the tape drive, the tape in the cartridge may be “mounted” byreading metadata on a tape and bringing the tape into a state where the LTFS is able to usethe tape as a constituent component of a file system. Moreover, in order to “unmount” a tape, metadata is preferably first written on the tape (e.g., as an index), after which the tape may be removed from the state where the LTFS is allowed to use the tape as a constituent component of a file system. Finally, to “unthread” the tape, the tape is unattached from the take-up reel and is physically placed back into the inside of a tape cartridge again. The cartridge may remain loaded in the tape drive even after the tape has been unthreaded, e.g., waiting for another read and / or write request. However, in other instances, the tape cartridge may be unloaded from the tape drive upon the tape being unthreaded, e.g., as described above.

[0135] Magnetic tape is a sequential access medium. Thus, new data is written to thetape by appending the data at the end of previously written data. It follows that when data is recorded in a tape having only one partition, metadata (e.g., allocation information) is continuously appended to an end of the previously written data as it frequently updates and is accordingly rewritten to tape. As a result, the rearmost information is read when a tape is first mounted in order to access the most recent copy of the metadata corresponding to the tape. However, this introduces a considerable amount of delay in the process of mounting a given tape.

[0136] To overcome this delay caused by single partition tape mediums, the LTFSformat includes a tape that is divided into two partitions, which include an index partitionand a data partition. The index partition may be configured to record metadata (metainformation), e.g., such as file allocation information (Index), while the data partition may beconfigured to record the body of the data, e.g., the data itself.

[0137] Looking to FIG. 9, a magnetic tape 900 having an index partition 902 and a datapartition 904 is illustrated, according to one approach. As shown, data files and indexes arestored on the tape. The LTFS format allows for index information to be recorded in the indexpartition 902 at the beginning of tape 906, as would be appreciated by one skilled in the artupon reading the present description.

[0138] As index information is updated, it preferably overwrites the previous version ofthe index information, thereby allowing the currently updated index information to beaccessible at the beginning of tape in the index partition. According to the specific exampleillustrated in FIG. 9, a most recent version of metadata Index 3 is recorded in the indexpartition 902 at the beginning of the tape 906. Conversely, all three versions of metadataIndex 1, Index 2, Index 3 as well as data File A, File B, File C, File D are recorded in thedata partition 904 of the tape. Although Index 1 and Index 2 are old (e.g., outdated) indexes,because information is written to tape by appending it to the end of the previously writtendata as described above, these old indexes Index 1, Index 2 remain stored on the tape 900 inthe data partition 904 without being overwritten.

[0139] The metadata may be updated in the index partition 902 and / or the data partition904 the same or differently depending on the desired approach. According to someapproaches, the metadata of the index and / or data partitions 902, 904 may be updated inresponse to the tape being unmounted, e.g., such that the index may be read quickly from theindex partition when that tape is mounted again. The metadata is preferably also written inthe data partition 904 so the tape may be mounted using the metadata recorded in the datapartition 904, e.g., as a backup option.

[0140] According to one example, which is no way intended to limit the invention, LTFSLE may be used to provide the functionality of writing an index in the data partition when auser explicitly instructs the system to do so, or at a time designated by a predetermined period which may be set by the user, e.g., such that data loss in the event of sudden power stoppage can be mitigated.

[0141] As mentioned above, magnetic tape is generally compliant with some predefinedtape format, such as LTO 9, LTO 10, etc. A format may specify servo track spacing, guardband location, number of tracks, and so on. Magnetic heads and their corresponding drivesare designed to comply with a particular format (or formats e.g., via reverse compatibility).Format specifications are generally available in the literature, and therefore readily availableto interested parties. Various approaches described herein may correspond to extant formats, modified versions of extant formats created according to the teachings herein, and / orcreation of a new format that could be, in relevant part, specified by one skilled in the artafter being apprised of the present disclosure and the teachings herein.

[0142] In some aspects described herein, a format may refer to a drive format, whichmay generally refer to a configuration of how the tape drive performs data operations, e.g., specifying such things as how much servo band guard to leave when writing, how much data track width to overwrite when performing shingled writing, what the nominal tilt angle of the transducer array is, etc.

[0143] Servo bands compliant with the desired tape and / or drive format are written onthe magnetic tape at the factory to ensure precise positioning of the servo tracks within theservo bands under ideal conditions to ensure consistency of the servo pattern, proper andconsistent spacing, and to minimize the detrimental effects of tape lateral expansion andcontraction. Moreover, servo tracks are not written by customer tape drives due to a varietyof reasons, such as the inherent variability between writer element spacing from module tomodule and drive to drive, the inability to ensure optimal conditions that avoid tape lateralexpansion or contraction, and so on, as would be apparent to unskilled in the art. Indeed,customer-level tape drives do not typically have built-in capabilities to write servo tracks,e.g., they do not have servo writers. It bears mention that some tape drives are able to write High Definition (HD) servo tracks that supplement the prewritten data band. The present disclosure is directed to servo bands prewritten on magnetic tapes according to a particular format.

[0144] It follows that the servo tracks prewritten on a magnetic tape are used throughoutthe life of the magnetic tape. Conventional wisdom has been to protect the servo tracks from overwrite to ensure their integrity, as damage to the servo tracks may render data on the tape unreadable. Accordingly, as shown in FIG.10, which is a partial representative view of a magnetic tape 1000 factory-formatted according to the LTO 10 format having two factory- written servo bands 1002, 1004 (three other servo bands not shown) flanking a data band area 1006. Unwritable guard bands 1008, 1010 are specified as being positioned between the data band area 1006 and each servo band 1002, 1004 adjacent thereto. The guard bands1008, 1010 are areas on the tape which are not written to, as specified by the format, to protect the servo bands 1002, 1004 from accidental overwrite.

[0145] Extant tape drives for large scale data storage use read / write heads with multiplereader elements and writer elements, and servo readers used to determine the position on thetape for reading and writing. The magnetic tape is segmented into ^^^data bands, DB, eachhaving a width ^^^; ^^^+1 servo bands, SB, of width ^^^; and two edge bands, EB ofwidth, ^^^^^; The data is written in the DBs by the ^^ writer elements and read back withthe ^^ reader elements. Extant drives use a 1-band head where the reader and writerelements write to only 1 DB at a time. For such a design, the ^^ reader or writer elementsare located sequentially, 1 to ^^on the read / write module separated by a fixed element pitch, ^^^. Extant heads locate one servo within a servo band separated from the nearestelement by ^^^. A writer element of width ^^ writes a wrap of data, then steps over by afixed track pitch, ^^^, overwriting a portion of the previous wrap leaving a shingled datatrack of width ^^^. To avoid overwriting data, the final track has a width ^^ rather thanthe desired width of ^^^. Accordingly, to first order, each writer element can fit ^^^^ =tracks, all but the final of width ^^^within a data sub band without overwritingthe data written in the adjacent tracks. The larger the element pitch, the higher the capacity.The width of the SB and the location of the servo readers is chosen to enable the dataelements to span the DB. Optimizing the capacity includes adjusting all parameters to satisfythe requirements, noting that all of the parameters are interconnected. With a single servoreader within each SB, the width of the SB is essentially ^^^ = ^^^ + ^^ − ^^^, where^^is the servo reader width.

[0146] One form of servo pattern is timing based. A chevron pattern is written in the SBvia magnetic bars written at angles relative to a line normal to the longitudinal axis of themagnetic tape. Simplifying the pattern to a V shape, on one edge of the SB, the time to crossthe two lines in the V near the apex is shorter for a given tape velocity. Moving to the wideend of the V, the time is relatively longer at the same tape velocity. Higher angle Vs enablebetter control, but the time to cross the two lines should be kept below a threshold. Forinstance, higher angles generally require narrower SBs. One method to reduce the width ofthe servo band, in accordance with one aspect of the present invention, is to place two servoreaders per SB (dual servo option) and each servo reader is used to write and read half thedata sub band. Thus the servo band may be reduced to about half the width needed for asingle servo reader option.

[0147] A dual servo design in accordance with one approach includes the followingtransducers: a group of two first servo readers (SG1a, SG1b), a group of ^^ data (reader orwriter) elements (EG), and a group of two second servo readers (SG2a, SG2b). SG1a andSG2a span their respective SBs, and during writing will be used to read from or write to halfthe sub DB. SG1b and SG2b also span their respective SBs, and during reading or writing, will read from or write to the second half of the DB. The dual servo option in one approachhas a servo band width W^^^SB of approximately: ^^^ =^+ ^^ − ^^^ (ignoring buffers).The dual servo option may serve two purposes: (1) enable a higher angle of the servo bandmarks since the maximum time to cross a servo band is cut in half; (2) enable highercapacity since the value for ^^^ may be approximately half the value used for the singleservo option.

[0148] The designs described in the previous three paragraphs are of a single band head,in which a single array of elements are flanked by a group of servos (1 or 2 per group) insurrounding SBs. A design in accordance with another aspect of the present invention is a 2-band head comprised of: servo group 1, element group 1, servo group 2, element group 2,servo group 3. Element groups 1 and 2 are configured to simultaneously write data in twoadjacent DBs. As with the single servo option, the dual servo option can be described as: SG1a, SG1b, EG1, SG2a, SG2b, EG2, SG3a, SG3b. An apparatus with such configuration,and as further described herein, optimizes the capacity written on tape and also greatlyincreases the rate at which data can be written or read, by operating on two data bands.

[0149] According to various aspects of the present invention described below, there isdescribed an apparatus having a magnetic head design which utilizes two servos per servoband and optimizes the capacity written to the tape. The design is fully symmetric, so thatalignment of reader and writer modules is versatile.

[0150] Particularly preferred approaches have the same number of data elements perarray as data channels, are fully symmetric, and optimize the capacity available on the tape. This is far superior to previous attempts which had an asymmetric transducer array, which limited versatility of its module. Moreover, designs utilizing an extra element per data band (e.g., 33 elements in the array, but only 32 active channels per data operation) were even less efficient in terms of data capacity on tape.

[0151] Other aspects of the present invention may include dual servo designs which arenot symmetric. For example, a dual servo design may be constructed to use media from asingle servo design so that ^^^is unchanged and the distance between one servo reader and the nearest data element is the same as the legacy design. In this case, adding a second servoreader results in an asymmetric design. Furthermore since ^^^ is unchanged, the capacityremains unchanged. Such a design has been patented and built. Furthermore, the designwhich was built and targeted for a product utilizes an extra element per data band making the design even less efficient for capacity.

[0152] Extant tape media used for data storage has several major regions: two edgeguard bands along opposite edges of the tape having a width ^^^^^; ^^^ data bands (one ormore); and ^^^ = ^^^ + ^ servo bands. No information resides in the edge guard bands.Data resides in the data bands and is written by writer elements and read by reader elements.The servo bands contain pre-written information about the location of the servo readerwithin the servo band. The servo readers read the information in the servo band and use it todetermine the location of the reader and writer elements within the data band. The tape headsinclude reader, writer, and servo elements. Writer elements (writers) write data to the media,reader elements (readers) read the written data, all within the data bands. Servo elements(servo readers) are positioned within the servo bands, and the servo bands are located oneither side of a data band. A servo band has a width, ^^^, and a data band has a width,^^^. Excluding any buffers, the width of tape, ^^^^^, is approximately the sum of theabove-mentioned regions:

[0154] The data band width is given by:

[0155] ^^^ = ^^ ∙ ^^^ 2

[0156] The data tracks are written with writer elements each having a width ^^ andread by reader elements of width ^^. The final tracks are spaced by a track pitch distance,^^^ which is less than ^^, via shingled writing of known type. A magnetic tape head hasarrays of ^^ elements (e.g., 16, 32, 64, 128 readers or 16, 32, 64, 128 writers) and a numberof read / write channels, ^^^. ^^ is equal to ^^^. On a tape head module, the data elementsare separated by a distance, ^^^or element pitch. Accordingly, for a single write pass of thetape, ^^ tracks of width ^^ are written and are separated by the element pitch distance,^^^. On the next pass, the location of the writer elements is stepped over by ^^^ andanother row of data is written of width ^^. The previously written track is partially written over, leaving data from the previous path with a width of ^^^(shingling). Ideally (excluding buffers and physical fluctuations), then each writer element can write ^^^^trackswithin the region spanning the element pitch minus the writer element width:

[0157] (^^^^ − ^) ∙ ^^^ = ^^^ − ^^ 3a

[0158] or ^^^^ = (^^^ − ^^ + ^^^) / ^^^ 3b

[0159] In the simplest case, only one servo reader is placed toward either end of themodule, flanking the array of ^^ elements. The servos would then need to move across theservo band a distance equal to this motion. Ideally, (excluding buffers and physical fluctuations), when the servo reader moves across the width of the servo band (^^^), thereader elements move across the element pitch, being placed half a track pitch (^^^) fromeither end of the element pitch. Thus,

[0160] ^^^ − ^^ = ^^^ − ^^^, 4a

[0161] or ^^^ = ^^^ + ^^ − ^^^. 4b

[0162] This is the densest packing of the data.

[0163] The servo readers are separated from the nearest element (S1-to-E1 and S2-to-^^^) by ^^^. In an ideal case, ^^^ is selected in order to place the edge of the servo at thetop of the servo band and the reader element centered one half a track pitch (^^^) from thetop of the data band:

[0165] The head span from one servo to the next, then, is given by:

[0167] The servo band-to-servo band spacing is then ^^^^^^^^^. Combining equations1, 2 and 4b yields:

[0169] Again, in the absence of buffers, the media and head are designed with theparameters: ^^^^^, ^^^^^, ^^^, ^^^^^^^^^, and ^^^. The heads are designed with theparameters: ^^, ^^^and ^^^. ^^, ^^and ^^^and can be modified to achieve the desired capacity using the base design.

[0170] A design which increases the capacity further by increasing the area available fordata is the dual servo option, in accordance with an aspect of the present invention.

[0171] The dual servo option utilizes two servo readers in each servo band, with spacingdefined byrepresenting the distance from the given servo reader tothe nearest element. For the dual servo option, the arrangement is: S1a, S1b, EG1, S2a, S2b,EG2, S3a and S3b representing three groups of a pair of servo readers (S1a+S1b, S2a+S2b,S3a+S3b) and two groups of data elements (element group 1 and element group 2, EG1, EG2)within each SB. In this example, S1a and S1b are each positioned a distance ^^^.^^^^and^^^.^^^^^from the first element in EG1, EG1.1. S2a is a distance ^^^.^^^^^from the lastelement in EG1, ^^^. ^^ and a distance ^^^.^^^^ from the first element in EG2, EG2.1. S2bis a distance ^^^.^^^^ from the last element in EG1, ^^^. ^^ and a distance ^^^.^^^^^ fromthe first element in EG2, EG2.1. S3a and S3b are respectively distances ^^^.^^^^^and^^^.^^^^ from the last element in EG2. Servo readers ^^^ are used to position writerelements to write data in one half of each DB in which EG1 and EG2 align and servo readers^^^ span the second half of the servo band, enabling writing in the other half of each DB. Thedesign is completely symmetric. The design can be used for either a 2-module, a 3-module, a4-module head design, etc. A 2-module design has two modules, each with a “piggy-backed”design where both reader and writer elements are deposited on each module. Data written bywriter elements from one module can be read with either reader elements in the same oropposite module. A 3-module design in one approach has two “outer” writer modules and acentral reader module (WRW configuration). One outer writer module writes in one directionof tape movement and the other outer writer module writes in the opposite direction of tapemovement. A 3-module design in another approach has two outer reader modules and a centralwriter module. The writer module writes in both directions, but one reader module reads inone direction of tape movement and the other reader module reads in the opposite direction oftape movement.

[0172] Any of the foregoing dual servo reader options may be extended to a triple servooption having three servo readers on each side of the data elements in an array. Thus, therespective servo readers may be used to read and write from approximately one third of the DB.

[0173] Writer elements are made by depositing metals onto a wafer in layers. A ring writerelement in some approaches has two poles at the tape bearing surface separated by a gap. Intape recording, the writing is done by the trailing edge, or the pole on the side of tape motion.Defining P1 and P2 as the poles deposited first and second in the wafer processing, depending on the orientation of the modules, either P1 or P2 will act as the trailing edge. It is possible that preferred writing is achieved by choosing either P1 or P2 as the trailing edge. Changingthe trailing edge may include rotating a module by 180 degrees. Because the present design isfully symmetric, the writer modules can be rotated 180 degrees and used for either P1 or P2 trailing without changing the drive code, saving time and money if the orientation needs to be changed. More details of exemplary designs according to various aspects of the presentinvention are given below.

[0174] FIG. 11 is a representation of regions on a magnetic tape, according to aconventional format. Two edge guard bands, each of width ^^^^^, are show, one on eitherend of the tape. No magnetic information is written in these regions. This is a four data bandtape format (^^^=4), labeled DB1 to DB4, each of width ^^^, and five servo bands, labeledSB1 to SB5, and each of width ^^^. The servo readers are designed to span the servo bandwhile writing data within each data band. A buffer is located at either end of a data band(data band guard) of width ^^^^ and on either end of the servo band (servo band guard) ofwidth ^^^^. The width of tape is given by Equation 9.

[0176] The addition in Equation 9 to Equation 1 are the servo and data band guards,which act as buffers between the servo bands and the data bands respectively to avoidoverwriting these regions.

[0177] Note that in viewing Figure 11, the parameter ^^^^ is not strictly needed, insome approaches, as it can be accounted for by modifying ^^^^ and ^^^^^. The benefit of^^^^is if one chooses to define media with ^^^^for the media and then add a drive protection of ^^^^, then the media and the head can account for the buffers differently. However, in various approaches, it is not necessary to include ^^^^:

[0178] {^^^^^, ^^^^^^ and ^^^^^ = ^} with ^^^^^ = ^^^^^ + ^^^^^, ^^^^^^ =^^^^^^ − ^^^^^. gives equivalent results to {^^^^^, ^^^^^, ^^^^^^ ≠ ^}.Often in the figures and text, ^^^^ is either set to 0 or simply ignored. To include it, simplyuse the math given above and redefine the parameters.

[0179] In the description of writing, data is written top-to-bottom of a data band forforward or even wraps and bottom-to-top for reverse or odd wraps. “Forward” and “even”are used interchangeably herein to describe forward wraps, as are “reverse” and “odd”wraps.

[0180] Method to Write Data

[0181] Determination of writing process focuses on the sub data bands.

[0182] FIG. 12 is a representation of a Data Band (DB) and Sub Data Bands, SDB. Thedata band is surrounded by two data band guards (DBGs), each of width ^^^^. The databand guards act as buffers between the data band and the surrounding servo bands. For atape head with ^^ reader and ^^ writer elements and a drive with ^^^ read / write channels,where ^^ = ^^^, the number of sub data bands is ^^. On the reader and writer modules,the elements (readers or writers) are all separated by an element pitch of width, ^^^. The width of the data band, ^^^, is given by the number of elements times the element pitch:

[0183] ^^^ = ^^ ∙ ^^^. 10

[0184] Each SDB has an outer buffer on either end with the width, ^^^^^^^ / ^. The datais written from the top of the SDB to the center on forward wraps and from the bottom of the SDB to the center on reverse wraps. An inner buffer of width, ^^^^^^, separates the last forward track from the last reverse track.

[0185] A total of ^^^^ wraps (or tracks) may be written. One half of the data tracks willbe even (forward) wraps and half will be in the odd (reverse) wraps. In this document, evenand forward are interchangeable as are odd and reverse. forward and reverse, simply indicatedirections of tape motion. These terms are also interchangeable in practice. For the first evenwrap, the writer element top edge abuts the lower edge of the top outer buffer. The data isshingled to a track pitch width, ^^^. The width of the even wrap data region within the SDBis ^^^ ∙ ^^^^ / ^. Thus, the writer element moves a distance, ^^^, given by:

[0187] An inner buffer of width ^^^^^^ is located between the even and odd wrapsregion to ensure that the data is not overwritten by the last even or odd written track. Thebottom of the final shingled track for the even wraps abuts the top of the inner buffer. For thefirst odd wrap, the bottom of the writer element abuts the top of the outer buffer at thebottom of the SDB. For the final odd wrap, the top of the writer element will be positioned ator slightly below the bottom of the inner buffer. This is to ensure that no data is overwritten.The width of the final odd wrap will then be the width of the writer element as it is notshingled. The data sub band width is the element pitch, which may be calculated usingEquation 12a:

[0191] ^^^^^ is a real number. Physically, the number of wraps an integer, ^^^^.Because the number of even and odd wraps is the same, ^^^^ is an even integer:

[0192] and ^^^^ = ^ ∙ ^^^^^(^^^^^ / ^), 12c12d

[0194] ^^^^^(^) is the mathematical function which rounds down to the nearest integer.

[0195] Because the buffers are much smaller than ^^^ and ^^, ^^^^ is primarily givenby ^^^ − ^^, so the wider the writer element, the lower the capacity.

[0197] The next step is to determine the width of the servo bands. Two preferred optionsfor servo-related configurations will be discussed below. The simplest is a single servo ineach servo band (single servo option). The second is using two separate servos, one to writethe even wraps and a second to write the odd wraps (dual servo option).

[0198] Single Servo Option for ^^ = ^^^.

[0199] FIG. 13 is a schematic of two servo bands surrounding one sub data band in thecase where ^^ = ^^^ = ^. The concept can be expanded to any case where ^^ = ^^^ +^. FIG. 13 demonstrates how the servo-to-nearest element distance (^^^ in FIG. 13) or theservo band width, ^^^, in FIG. 13 is sufficient for any ^^. For ^^ > ^, the length of thedata band region is ^^^, given by Equation 10. Shown are the top and bottom servo bandswith the servo band guards (labeled Servo Band Guard), the data band guards, the data bandguards (labeled Data Band Guard), between the servo bands and the data band. Only a singleSDB is shown, since this is pictorially easier than showing all SDBs on a tape havingmultiple SDBs.

[0200] Using a single servo reader when the number of channels is equal to the numberof elements, ^^^ = ^^, the width of the servo band and the distance between the servoreader and the nearest element, ^^^.^^^^^^, (simply ^^^in FIG.13), can be explainedusing FIG. 13. The subscript “SE” indicates servo-to-element, and "^^^^^^" indicates ^^is an even number. Because the center of the reader element istop ofthe SDB for the first even read wrap and from the bottom of the SDB for the first odd readwrap, the reader element moves a distance:

[0201] ^^^.^ = ^^^ − ^^^ − ^^^^^^^^ . 13a

[0202] The servo reader moves the same distance. The top edge of the servo reader abutsthe top of the SB for the first even read wrap and the bottom edge of the servo reader abutsthe bottom edge of the SB for the first odd wrap so the center of the servo reader is^^fromthe top and bottom edge of the SB for the first even and odd wraps respectively. ^^ is theservo reader width. Thus, the width of the servo band is:

[0204] The distance between the center of the top servo reader and the center of the firstreader element can be determined as depicted in FIG. 13 for the first even read with thedistance ^^^.^^^^^^labeled as ^^^.^^^^^:

[0206] Combining 13b with 14a yields:

[0207] ^^^^^^^^^^^^^^^^.^^^^^^ = ^^^ + ^^^+ ^^^^ + ^^^^. 14b

[0208] By symmetry, the distance from the lower servo reader to the last reader elementis also given by Equation 14b. Note that the actual width of the data band is given by Equation 8 for ^^elements, but for explanation purposes a single SDB is sufficient and easier to show pictorially.

[0209] Equation 9 gives ^^^^^ as a function of unknowns ^^^ and ^^^; Equations 10and 13b respectively give ^^^ and ^^^ as a function of ^^^. Combining Equations 9, 10and 13b allows one to solve for ^^^, as follows:

[0213] Error in 15b is ~300 nm.

[0214] ^^^ can be determined using Equation 13b using the value for ^^^ fromEquation 15a.

[0215] The servo reader-to-servo reader span, ^^^^^^^^^^.^^^^, is given by:

[0219] Single Servo Option for ^^ = ^^^ + ^.

[0220] Another option, in accordance with one aspect of the present invention, is to use asingle servo reader per servo band when the number of elements is one more than thenumber of channels, ^^ = ^^^ + ^. FIG. 14 shows a schematic of two servo bandssurrounding two sub data bands in the case where ^^ = ^ and ^^^ = ^. The concept canbe expanded to any case where ^^ = ^^^ + ^. The data band width is now given byEquation 17.

[0221] ^^^ = ^^^ ∙ ^^^ = (^^ − ^) ∙ ^^^. 17

[0222] A total of ^^^^ wraps (or ^^^^) may be written. Half will be in the even wrapswritten in forward (Fwd.) direction and half will be in the odd wraps for the reverse (rev.)direction. In the forward wraps, the last element is not used, data is written in the top half ofthe data sub bands and the servo reader uses the bottom half of the servo band. Thus, theposition of the writer element in the last even wrap defines the lowest location of the servoreader in the servo band. In the reverse (rev.) wraps, the first element is not used, data iswritten in the bottom half of the data sub bands and the servo reader uses the top half of theservo band. Thus, the position of the writer element in the last odd wrap defines the highestlocation of the servo reader in the servo band. The distance the servo readers move, ^^^,then, is given by:

[0223] ^^^^ = ^^^−^^. 18a

[0224] The writer elements move the same distance given as:

[0226] Combining Equations 16a and 16b gives ^^^.

[0228] FIG. 14 shows the concept for the wraps and Equations 12a-d still determine^^^^. Combining Equation 12b (with ^^^^ = ^^^^^) yields:

[0229] 18d

[0230] Equation 9 gives ^^^^^with unknowns ^^^, and ^^^. Equations 17 and 18drespectively give ^^^, and ^^^in terms of the unknown ^^^. Combining Equations 1, 17 and 18d yield a solution for ^^^:

[0232] The distance between the center of the top servo reader and the center of the firstwriter element, ^^^.^^^^^, can be determined as shown in FIG. 14 for the forward wraps:half the servo reader width plus the servo band guard, plus outer buffer / 2 plus the distancethe writer element move in forward wraps (Equation 11. ^^^∙ ^^^), plus,half the writer Width:

[0234] Taking Equation 20a and replacing ^^^^ with ^^^^^ from Equation 12b yields:

[0236] Note that, for ^^ = ^^^ + ^, (i.e. odd ^^), the distance of the servo reader tothe nearest element is approximately half the element pitch plus half the servo reader width((^^^ + ^^) / ^) while the even ^^ case the distance is approximately one element pitchplus half the servo reader width (^^^

[0237] The servo reader-to-servo reader span, ^^^^^^^^^^.^^^, is given by:

[0240] Thus, ^^^^^^^^^^.^^^~^^ · ^^^ + ^^. 21c

[0241] Thus, for the two options of even and the odd ^^, both the data band width andthe servo reader-to-servo reader span values (16c & 21c) are essentially the same.

[0242] Dual Servo Option for ^^ = ^^^.

[0243] FIG. 15 shows a schematic of a single band head with dual servo readers perservo band. The elements, E.1 to ^. ^^ can be either a group of ^^ reader elements, R.1 to^. ^^, or writer elements, W.1 to ^. ^^. The servo readers work in pairs: {S1a and S2a}for forward or {S1b and S2b} for reverse reading and / or writing.

[0244] FIGS. 16A and 16B, respectively, are schematics of two servo bands surroundinga single Sub Data Band, SDB, for (16A) forward and (16B) reverse writing and reading. Theactual length of the data band region is ^^^, given by Equation 8. As will be shown later,the distance from one of each servo reader pair to the nearest element is ^^^.^^^^^ (alsoreferred to herein as WSE.Short.Head) while the second servo reader in the pair has a distance(same as WSE.Long.Head) with the subscript “SE” referring to servo reader-to-element and the subscripts “Short” and “Long” for relative distance. The concept can beexpanded include any number of SDBs. FIGS. 16A and 16B demonstrate how to determinethe distances from a servo reader to the nearest element and the servo band width. FIGS. 11-12 and Equations 1 and 10 may be used for determining servo reader-to-servo reader spansand element pitch for ^^^>1, and the length of the data band region is ^^^, given byEquation 10. Shown in FIGS. 16A and 16B are a top servo band (toward top of page) and abottom servo band with the servo band guard (labeled “Servo Band Guard”), the data bandguards (labeled “Data Band Guard”), and the data band guards between the servo bands andthe data band.

[0245] The positioning of the servo readers will now be described. Focusing on FIG.16A for the forward wraps, ^^^ spans the top servo band and ^^^ spans the bottom servoband. The distance between the center of the top servo reader and the center of the firstreader element may be determined as follows: the highest location of the servo reader isduring first forward read wrap. The top edge of the top servo reader abuts the lower edge ofthe top servo band and the reader elements are located half a track pitch below the top outerbuffer. Thus, the distance from the top servo reader, ^^^, to the first reader element, (e.g., ^^in FIG. 15), is ^^^.^^^^^, and is given as:

[0247] This is the same Equation as used for the Single Servo option, but ^^^ isdifferent as shown below. Here is where the difference occurs. For the first forward wrap,the top edge of the servo reader used in the lower servo band abuts the lower edge of the topservo band guard in that servo band (e.g., the top edge of the bottom servo band in FIG.16A). The separation from the last reader element, ^^^, to the lower servo reader, ^^^, islabeled ^^^.^^^^.

[0249] The primary dimension determining the distance between the servo reader andthe closest reader element is ^^^ for ^^^.^^^^^ and ^^^ for ^^^.^^^^. Because each pairof servo readers only spans half the data band for the even wraps, ^^^~^^^ / ^, as will beshown below.

[0250] The odd wraps also use a pair of servo readers, and by symmetry, they have thesame dimensions as the even wraps, except they are reversed, with ^^^.^^^^ (with ^^^.^^^^)being in the top servo band and ^^^.^^^^^ being in the bottom servo band. Thus, the order ofelements from top to bottom is: ^^^^^, ^^^^^^, ^^ elements, ^^^^^^, ^^^^^, or in FIG. 15:^ , ^^ elements, ^^^, ^^^. The servo reader Span, or distance from the topreader to the bottom servo reader is then:

[0252] The reverse wraps, shown in FIG. 16B, are similarly analyzed with the sameresults.

[0253] The next step is to determine the length of the servo band. Observing FIG. 16A,^ the top of the servo band is a distance^above the center of ^^^positioned for the firstforward read wrap. For the first forward write wrap, the writer elements are positioned so thetop edge of the writer element abuts the lower edge of the top outer buffer region (width^^^^^^^ / ^ ). For the first forward wrap, the distance between the center of the writerelement and reader element is ^^^^^^^^^^:

[0255] The writer element writes ^^^^ wraps, stepping a distance ^^^ per wrap (seeFIGS. 12 and 16A). The distance moved, ^^^, is then:

[0257] The lower edge of the servo reader abuts the top of the lower servo band guard,^ which is^ below the center of the servo reader. The servo band width, ^^^, is given by thesum of the terms described above.

[0259] Combining Equations 25, 26 and 27a gives:

[0261] Substituting Equation 10b into 27b (using ^^^^ for ^^^^^ from 12b) yields ^^^in terms of ^^^:

[0265] Or to within the width of ^^:

[0266] ^^^^^^~^. 27e

[0267] The final dimension to calculate is ^^^, which is solved using Equation 9 for^^^^^, which contains the dimensions ^^^(Equation 8) and ^^^(Equation 20c):

[0268] ^^^ =

[0269] The optimum choice of element pitch, ^^^, is determined using the tape inputvalues of tape width ^^^^^, edge guard band width ^^^^^, number of data bands ^^^, andthe head / drive parameter of the number of elements ^^ and the servo band guard ^^^^ anddata band guard ^^^^ and the outer and inner buffers ^^^^^^^ and ^^^^^^ chosen fordrive operation. To first order, ^^^is:

[0271] ^^^ can be further approximated with a loss of ~1% in accuracy as:

[0273] Which, to first order, is the used portion of tape (^^^^^ − ^ ∙ ^^^^^) divided bythe total number of sub data bands (^^ ∙ ^^^).

[0274] Head Assembly / Alignment, 1-Band Head and Dual Servo Option

[0275] A 1-band head is one in which the elements span a single band, surrounded byservo bands. FIG. 15 is a schematic for a 1-band head with ^^ elements utilizing the DualServo Option. FIGS. 16A and 16B describe the operation of forward and reverse writing / reading for a 1-band head. In practice, reader and writer elements should be aligned in theintended direction of tape travel thereacross to enable operation in read-while-write andread-only modes.

[0276] FIG. 17 shows the alignment and assembly schematic for a 3-module headalignment with Left Writer (LW), Right Writer (RW) and Center Reader (CR) modules. Tomatch FIG. 17 alignment with FIGS. 16A and 16B, the arrays shown in FIG. 17 are rotated90 degrees clockwise. LW refers to media traveling from left to right in FIG.16A forforward motion; thus LW will be writing, and the Center Reader, CR, will be reading evenwraps. RW refers to media traveling from right to left in FIG. 16B, so LW will be writingand the Center Reader, CR, will be reading odd wraps. For forward wraps, servo readers,^^^and ^^^will be used by both the CR and the LW, so ^^^and ^^^are “hashed out” inFIG. 17 for the LW. For reverse wraps, servo readers, ^^^ and ^^^ will be used by both theCR and the RW, so ^^^and ^^^are “hashed out” in FIG.17 for the RW.

[0277] Head Assembly / Alignment, 2-Band Head and Dual Servo Option

[0278] A 2-band head is one in which the elements span two bands. Particularly, half thedata elements are used in one band and the other half are used in an adjacent band, with threegroups of servo readers in three servo bands in a preferred approach. For a 2-band head, themedia should have an even number of data bands with data being written to, or read from,two adjacent data bands simultaneously. The arrangement during read or write is, in oneapproach: SB, DB, SB, DB, SB.

[0279] Preferably, data elements operate simultaneously to write and / or read data in bothdata bands simultaneously. Conventional encoding and decoding techniques may be appliedto the groups of data elements in both data bands, in a manner that would become apparent to one skilled in the art after reading the present disclosure. For example, in one approach,the two groups of elements above the two data bands operate together as one larger array.Thus, for example, if there are 32 writers in each group for a total of 64 writers across both data bands, a single stream of data may be deserialized for concurrent writing using writers in both groups, i.e., data from the single stream is written concurrently into both data bands,preferably along with error correction encoding of known type. In another approach, each group of writers operates independently, e.g., for concurrently writing two streams of data to the two data bands, for concurrently writing alternating chunks from the data stream that areheld in a buffer associated with each group so as to maintain constant writing, etc.

[0280] FIG. 8 is a schematic for a 2-band head with ^^ elements in each Group (A andB) utilizing Dual Servo Option for a 3-module head alignment with a Left Writer (LW), aRight Writer (RW), and a Center Reader (CR) module, in accordance with one approach. Tomatch FIG. 8 alignment with FIGS. 13 and 14, the arrays shown are rotated 90 degreesclockwise. LW refers to media traveling from left to right in FIGS. 13 and 14; thus LW willbe writing and the Center Reader, CR, will be reading even wraps (forward or Fwd.). RWrefers to media traveling from right to left in FIGS. 13 and 14; thus RW will be writing andthe Center Reader, CR, will be reading odd wraps (reverse or rev.). S servo readers, ^^^, willbe used for even (forward) wraps and T servo readers, ^^^, for odd (reverse) wraps (or viceversa).

[0281] As described earlier, a 3-module head is not the only functional design for alinear tape product. One could also build a 2-module head which has both reader elementsand writer elements on each module.

[0282] FIG. 19 shows a schematic of a 2-module, 1-band head with ^^ elementsutilizing Dual Servo Option for a 2-module head alignment with a Left Head (LH) and a Right Head (RH), both with ^^Readers and ^^Writers.

[0283] For the 2-module head, the servo readers may be placed in the line of the readerelements in the design, and accordingly may be built in the same process on the wafer.While it is possible to make multiple process steps in the wafer build, to place the reader elements and servo readers in different layers, it is substantially more expensive. The writerelements are preferably placed on the outside of the head since the reader elements from thesame module will read while the writer elements are writing. In forward motion, thedirection of tape movement is from bottom of the LH from the writer side to the reader side.For reverse writing, the direction of tape movement is from the top of the RH from the writerside to the reader side. For read-while-write, reading from the same module as writing hasthe advantage for alignment, especially in the case of the rotated head where alignment willbe better. It is equally possible to reverse the ordering (i.e., rotate both modules around 180degrees) and reverse the ordering of the module read / write. Another possibility is to writeusing one module and read using the second module.

[0284] Because of the cost of a wafer and servo writer for the media, a general design isoften reused for several generations. The head design of element pitch and servo readerlocations remain fixed and only parameters such as reader element and writer element widthsand track pitch are changed to achieve higher capacity. The media servo pattern locations and widths remain unchanged, only modifying the media properties such as magnetic layers,surface roughness, substrate thickness and length for enabling higher capacity.

[0285] The change in the optimum element pitch is not affected by the writer elementwidth. ^^^^^^^^.^^^^^^

[0286] ^^.^^^^^^^^= ^^^= ^^^ =0 30

[0287] The dependence on optimized ^^^ and a change in ^^^ is given by:

[0289] For ^^ = ^^ and ^^^ changing from 500 to 200 nm, the change in the optimum^^^is only 4.7 nm. By using a design calculated for a fixed ^^^of say 350 nm to optimize for track pitches ranging from 500 to 200 nm, the head will function for the full range with minor or no reduction in the capacity (^^^^) for a ^^^other than 350 nm.

[0290] The change in ^^^.^^^^ and ^^^.^^^^^ with changes in ^^^ are given here:

[0292] A change in ^^^ by ±150 nm will change the optimum ^^^.^^^^ and ^^^.^^^^^by ±75 nm, which is minimal with buffers of 1 mm or more. By using a design calculated fora fixed ^^^ of ^^^.^^^ = ^^^ ^^, the head will function for the full range with minor orno reduction in the capacity (^^^^) for ^^^ other than 350 nm. Because the design isspecific to a given media format, the locations and sizes of the servo patterns remainunchanged resulting in only minor or no reduction in the capacity achieved compared to the optimum.

[0293] Head Design

[0294] Reader and writer tape modules as described herein may be fabricated usingknown techniques. In exemplary fabrication processes, material is deposited onto a ceramic substrate. The deposition is built vertically. For a ringed writer, the first pole deposited is termed P1 and the latter deposited pole is P2. From the tape bearing surface, TBS, one seesthe outline of P1, a gap of non-magnetic material, and P2.

[0295] Moreover, the values used for the variables in any of the Equations listed hereinmay be any number desired by the designer, so long as the final numbers all work together inan operable apparatus or tape product, as would be apparent to one skilled in the art after reading the present disclosure. Typically, some of the values are selected to provide a desired function or are prespecified. Such values selected or prespecified may include tape width, data element width, servo reader width, number of data bands on tape, etc.

[0296] FIGS. 20A and 20B are schematics for a 1-band head with ^^ elements utilizingDual Servo Option for a 3-module head alignment with a Left Writer (LW) and Right Writer (RW) and Center Reader (CR) modules, in accordance with various approaches. The LW and RW respectively write while media moves from left-to-right and right-to-left. In FIG. 20A, writer pole P2 is the trailing edge. In FIG.20B, writer pole P1 is the trailing edge. Because of processing constraints, the geometry of P1 and P2 are often different. The trailing pole material dominates the quality of the written magnetic bit transition. Because of differences in processing, either P1 or P2 trailing may be preferable. With the symmetric design described in this disclosure, one can use either P1 or P2 trailing without modifyingthe drive code. Because of the long time and large cost in building wafers and developingdrive code, the versatility in enabling either P1 or P2 trailing designs with the same wafer is highly beneficial in time, effort, and cost.

[0297] Apparatus

[0298] An apparatus, in accordance with one approach, includes a magnetic head havingan array of transducers, the transducers comprising data elements such as read elements or write elements, at least two first servo readers positioned toward a first end of the array and at least two second servo readers positioned toward a second end of the array. The dataelements and servo readers may be of any type mentioned herein and may be constructed viaknown techniques. The servo readers are preferably generally aligned with the data elements along the longitudinal axis of the array, the servo readers being positioned relative to the data elements to enable positioning of the data elements within a data band of a magnetic tape based on readback signals from at least some of the servo readers reading the servo bands that flank the data band. The array of transducers is symmetrical about a centerpoint thereof, such that a distance between a center of an innermost one of the first servo readers and a center of the data element closest thereto is the same as a distance between a center of an innermost one of the second servo readers and a center of the data element closest thereto, and such that a distance between a center of an outermost one of the first servo readers and the center of the data element closest thereto is the same as a distance between a center of an outermost one of the second servo readers and the center of the data element closest thereto.

[0299] In a preferred aspect, only two of the first servo readers and only two of thesecond servo readers are present in the array. For example, FIG.20A depicts such an approach, where S1a and S1b are the first servo readers in each array, while S2a and S2b arethe second servo readers in each array. See also FIGS. 15-17 and 19-20B.

[0300] The various dimensions of the respective components of the apparatus, and theirrelative positioning, may be as listed or suggested elsewhere herein. In one exemplary approach, an average pitch WEP.Head of the data elements is in a range of 86 to 97 microns, a center to center distance WSE.Shortbetween the data element closest to the first end of the array and the first servo reader closest to the data elements is in a range of (WEP / 2) + 3 to (WEP / 2) + 10 microns, a center to center distance WSE.Long between the data element closest to the first end of the array and the first servo reader farthest from the data elements is in a range of WEP+ 3 to WEP+ 10 microns, a center to center distance between the data elementclosest to the second end of the array and the second servo reader closest to the data elementis about equal to WSE.Short, and a center to center distance between the data element closest to the second end of the array and the second servo reader farthest from the data element isabout equal to WSE.Long.

[0301] In one approach, the data elements are writer elements, and the magnetic headincludes a second array aligned with the array in an intended direction of tape travelthereacross, the second array comprising read elements e.g., in a read-while-writearrangement. At least two third servo readers positioned toward a first end of the second array and at least two fourth servo readers positioned toward a second end of the secondarray. The second array is also symmetrical about a centerpoint thereof, e.g., as if the arraywere folded over on the centerline such that the second end of the array overlies the first end of the array. This feature enables read-while-write, which is important for data verification.

[0302] As described in more detail below, a longitudinal axis of the array may benominally tilted by greater than 0 degrees, e.g., greater than 1 degree, greater than 2 degrees, preferably greater than 5 degrees, etc. from normal relative to an intended direction of tape travel thereacross. The maximum nominal tilt may be about 15 degrees. Thus, the actual nominal tilt may be any value in the range of greater than 0 and about 15 degrees. The range of tilt may be from 0 to about 20 degrees, ± some value from the nominal tilt (e.g., <5 degrees, <3 degrees, etc.). The tilt provides a predefined “effective” element pitch, and enables compensation for tape lateral expansion and contraction by adjusting the tilt, which in turn increases or decreases the effective element pitch. For example, reducing the tiltincreases the effective pitch.

[0303] In one approach for performing data operations on two data bands, a second arrayof transducers is aligned along a longitudinal axis of the array. See, e.g., FIG. 18. A first endof the second array is positioned adjacent the array. The second array of transducers comprises second data elements and at least two third servo readers positioned toward a second end of the second array. The distance between the center of the innermost second servo reader and a center of the data element of the second array closest thereto is the same as the distance between the center of the outermost first servo reader and the center of the data element closest thereto, as shown in FIG.18. The distance between a center of the outermost second servo reader and a center of the data element of the second array closest thereto is the same as the distance between the center of the innermost second servo readerand the center of the data element closest thereto, as also shown in FIG. 18. The combinedarray consisting of the array and the second array is ideally symmetrical about a centerpoint of the combined array.

[0304] As mentioned above, the various dimensions of the respective components of theapparatus according to the many approaches described herein, and their relative positioning,may be as listed or suggested anywhere herein. Accordingly, dimensions such as the averagepitch WEP.Head of the data elements; the distance WSE.Short.Head between the center of the innermost first servo reader and the center of the data element closest thereto; the distance WSE.Long.Headbetween the center of the outermost first servo reader and the center of the data element closest thereto; the distance WServoSpan.Head between the center of the innermost one of the first servo readers and the center of the outermost one of the second servo readers; and so on may satisfy any of the corresponding equations presented herein.

[0305] Tilted Head for Tape Dimensional Stability Compensation.

[0306] In writing data to tape with a multi-element read / write head, the spacing betweenelements can increase or decrease due to changes in spacing on the head and / or in the media.Expansion or contraction of the head and / or media width due to thermal changes, humiditychanges, and / or other stresses can occur. One mechanism for correcting for these changes isto tilt the head at an angle relative to the track direction. For example, if the media moves in the x direction and the track pitch is in the y direction, rotating the head by an angle q relative to the y axis will shorten the track pitch in the frame of the tape, and thus, theeffective track pitch as presented to tape is shortened. The apparatus can be built with anominal value of ^^, and active tilting of the array to change q can be performed to changethe effective transducer pitch as presented to tape. The analysis given so far can be generalized to include the head tilt concept by analyzing the dimensions in the reference ofthe media. For example, assume the media dimensions, ^^^^^^, are fixed and the head dimensions, ^^^^^, are translated to the media reference plane by multiplying by ^^^(^^). The calculations for the head dimensions for parameter X, ^^.^^^^, are then done in the reference plane of the media as transformed dimensions, ^^.^^^^and visa versa:

[0308] Media parameters include:^^^^^, ^^^^^, ^^^, ^^^^ , ^^^, ^^^^ , ^^^^^^^ , ^^^^^^ ^^^ ^^^, as describedelsewhere herein.

[0309] Head parameters include: ^^ , ^^, ^^, ^^^ ^^^, as described elsewhereherein.

[0310] FIG. 21 shows the concept of tilting pictorially, e.g., for TDS compensation,whereby said concept may be applied to various aspects of the present invention, as would become apparent to one skilled in the art after reading the present disclosure. The Pisa angleis the nominal angle q of tilt.

[0311] Following are exemplary guidelines for designing an apparatus that implementshead tilt.

[0312] A head dimension used for determining the element pitch is the servo readerwidth. Thus, for a tilted head, the dimensions of the element pitch on tape,isderived from Equation 28 using the servo reader width converted to tape dimension, ^^ →^^ ∙ ^^^ (^^), and with ^ ∙ ^^^ ∙ ^^^^ = ^:

[0313] ^^^.^^^^ =

[0316] The error in ^^^.^^^^ using Equation 34b is approximately.

[0317] 34d

[0318] For ^^^^^ = ^^, ^^^ ^^ and ^^^^^ = ^^^ ^^, Equation 34b yields^^^.^^^^ = ^^. ^^ ^^. With ^^^^ = ^, ^^^ = ^, ^^ = ^^, ^^ = ^ ^^, ^^ =^^ ^^^, ^^^^ = ^ ^^, and ^^^^^^^ = ^^^^^^ the error in ^^^.^^^^, ∆^^^.^^^^^, is^. ^^ ^^ or 0.2%. ^^^.^^^^ can be further approximated to:

[0320] With ^^^ = ^ and ^^ = ^^, the additional error is about 2%:

[0321] 34f

[0322] The element pitch on the head is determined using Equation 33 as:

[0324] Combining Equations 34b and 35a yields an approximation for ^^^.^^^^ to anaccuracy of 0.2% of:

[0326] Equation 35b can be further approximated combining 34c with 35a to anaccuracy of about 2%:

[0328] The servo buffer is converted from Equation 27c to:

[0330] The servo buffer on tape is approximated by:

[0332] The error in Equation 36a using 36b is:

[0334] With ^^^^^^^ = ^^^^^^ = ^. ^^ ^^, and ^^^.^^^ = ^. ^^ ^^, and ^. ^ ^^ ≤^^^ ≤ ^. ^ ^^, the error in ^^^.^^^^ using the approximation of 36b rather than 36a isbetween −^. ^ ^^ and −^. ^ ^^, which is easily accounted for with a^^^^ ^^^^^^^ ^^^^^ ^ ^^ ^^ ^^.

[0335] Inserting Equation 34e into 36b yields:

[0336]

[0337] ^^^.^^^^ , can be further reduced to half the element pitch:

[0338] ^^^^.^^^^^^^^^^^∙^^^^^^^.^^^^~^ = ^∙^^∙^^^ . 36e

[0339] The error in using Equation 36e rather than 36d is primarily from ^^, which canbe up to about ^ ^^ which is on the order of a 4% error.

[0340] Another important parameter for the tape is ^^^^^^^^^^.^^^^, which is the distancefrom the center of one servo band and the next. This can be derived in two ways. Onederivation of ^^^^^^^^^^.^^^^is by viewing the physical distance between the center of thetwo servo bands in FIGS. 16A and 16B. Setting ^^^^ = ^:

[0341] ^^^^^^^^^^.^^^^ = ^^^.^^^^ + ^^ ∙ ^^^.^^^^ + ^ ∙ ^^^^ 37

[0342] The second means to derive ^^^^^^^^^^.^^^^^^ is using the servo band dimensions,^^^.^^^^^, and ^^^.^^^^ using Equations 22, 23 and 24 with 33. Setting ^^^^ = ^ yields:^^^^. 38c

[0346] For tape dimensions, only the term in 38c, ^^^^^^^^^^.^^^^, is relevant. TheMedia used is defined by the dimensions: ^^^^^, ^^^^^, ^^^.^^^^ , ^^^^^^^^^^.^^^^, and^^^^. Inserting Equations 38a and 38b into Equation 38c yields ^^^^^^^^^^.^^^^:

[0347] ^^^^^^^^^^.^^^^ = ^^^.^^^^ + ^^ · ^^^.^^^^ + ^ · ^^^^. 39

[0348] Equations 37 and 39 agree.

[0349] ^^^.^^^^ and ^^^.^^^^ are given by Equations 34a and 36a or approximated as 34band 36d. Variations in the actual values of ^^^^^and ^^^^^of even 10s of microns don’t substantially affect the results since end results are the head parameter definitions, and the tape definitions

[0350] Next is the calculation of the head parameters.

[0351] ^^^.^^^^ can be converted from Equation 36d with 33 to ^^^.^^^^:

[0352] ^^^.^^^^~

[0353] Note that a wafer design for a head is often used for multiple product generationsusing different track pitches, ^^^, on the tape to achieve higher data capacities per generation.These different generations may need to operate with the same head spacings of ^^^,^^^.^^^^, ^^^.^^^^^, etc., with only the reader and or writer element widths and gaps changing.Thus a design may be chosen which functions for the potential future capacities or ^^^ values.An option is to calculate and use the average or median ^^^for these generations in the Equations, which is what ^^^.^^^represents. ^^^.^^^could also be the target ^^^for a single use.

[0354] Note that, ^^^.^^^^ is not a physical parameter of the head and is only useful forcalculations.

[0355] Inserting ^^^.^^^^ from Equation 36b into 39 yields:^^^.^^^. 41

[0357] Inserting ^^^.^^^^ from Equation 34b into 38b yields:

[0359] with ^^^.^^^^ given by 34b or 34e with respective errors of 0.2% and 2%.

[0360] To set the media specifications, the designers may define ^^^^^, ^^^^^,^^^.^^^^, and ^^^^, calculate a ^^^^^^^^^^.^^^^. The specifications then define a nominaltape width with a loose tolerance, such as 10 mm to 20 mm width dimension, or whatevertolerances allow for physically running the tape. The specification on ^^^^^^^^^^.^^^^must be tightly defined within a range that can be compensated for environmental and agingchanges, preferably within ±1 mm. ^^^.^^^^ can then be set to be the calculated value as theminimum, ^^^.^^^^. ^^^ as the value in Equation 36b, and the maximum adding^^^.^^^^ . ^^^ + ^^^^.

[0361] Now for the head definitions. Repeating Equation 35b for the element pitch onthe head, ^^^.^^^^, for an accuracy of about 0.2%:

[0363] Or repeating Equation 35c for the element pitch on the head for an accuracy ofabout 2%:

[0365] Next is the servo reader locations. ^^^.^^^^^.^^^^ is calculated from Equations38a with 33.

[0367] Removing the contribution from ^^^^^^^^ and replacing ^^^ with ^^^.^^^and using Equation 42 for ^^^.^^^^gives:

[0369] With ^^^.^^^ = ^^^ ^^ and ^^^ = ^^^ ± ^^^ ^^ and^^^^^^^^~^^^ ^^, the error in ^^^.^^^^^.^^^^ using Equation 44b rather than 44a isbetween 50 and 200 nm.

[0370] ^^^.^^^^.^^^^ is calculated from Equation 38b with 33:

[0372] Removing the contribution from ^^^^^^^^ and replacing ^^^ with ^^^.^^^,45a becomes:

[0374] ^^^^^^^^^^.^^^^ can be calculated as:

[0376] Combining Equations 44b and 45b into 46a yields:

[0378] Exemplary Chip Dimensions

[0379] The tape head module and chip dimensions are specified prior to production. Awafer contains many tape head chips. The chip is defined as the wafer portion containing allthe elements. The chip is then attached to a module. For a tape head, the center of the designis centered on the module. The module, in-turn, may be centered over the tape. The width ofthe chip may or may not span the width of the module.

[0380] FIG. 22 depicts a head chip (Head Chip) overlaying a tape (Tape). The head chiphas a dual-band head design with two servo readers per band. The depicted features of thehead chip and tape shown in FIG. 22 can be used to explain both dual-band and a single-band head design to determine the dimensions. Preferably, the head chip extends beyond theedge of the tape by a minimum distance, ^^^^^^^^. In calculating the requisite width of thechip to ensure the tape is always supported by the chip, it is assumed that ^^^^^^^^ is large(^^ ^^^^^^^^ > ^^^ ^^). Thus, the relevant parameters can be approximated by theirterms which are at least 10s of microns. Thus ^^^^and ^^can be ignored. The ^^^(^^)term to convert from tape reference to head reference is significant across the width of thetape. Note that ^^^^^ and ^^^^^ are in the tape reference frame, so no subscript is needed.The calculation will be first done in the reference frame of the tape, and then converted tothe head / chip reference frame using Equation 33:

[0381] ^^ ^^ ^^.^^^^~ ^^^^∙^^^^^ , 46a^^∙^^^^^^^^^^^^

[0386] Viewing FIG. 22, the distance from the center of the 1-band design to the furthestedge of the chip, ^^^^^.^^^^^.^^^^, is:

[0389] ^ .^^^^^.^^^^~^^^^^ −^^^^^^^^^^ ^^^^^ − ^^^^ − ^^^ ∙ ^^^.^^^^ + ^^^^^^^^47b

[0390] To determine the width in the head reference frame, simply divide by ^^^(^^)and using the approximation for ^^^.^^^^^.^^^^in Equation 46d:

[0392] The dual-band design will have two groups of ^^ elements. For a 4-band media,data bands, DB1 and DB2 will be written to simultaneously as will DB3 and DB4. Thus, for the dual-band design, the required distance to the edge of the chip will be less by the shift from the center of the Group 1 to the center of the 2-band design:^^^.^^^^^.^^^^^^^^.^^^^.^^^^^ 48a

[0394] Combining Equations 47b and 48a and with 46c, 46d and 10 yields:

[0398] The N-band head will have the design center aligned with the module center witha minimum extension of the chip from the center being ^^^^^.^^^^^.^^^^where N=1 or 2 are defined by Equations 47b and 48c.

[0399] FIG. 23 is a schematic of the alignment on a module 2300 of a dual-band headdesign with two servo readers 2302 per band for use in a tape drive with, as shown in part(a), 1-band of ^^ channels, or as shown in part (b), 2-bands of ^^^^ channels. Both typesof modules use the same 2-band design with ^^^^ channels to reduce the cost of buildingtwo wafer designs. As noted in comparison of FIG.23 and Equations 47b and 48c, the widthof the 1-band module is longer than the width of the 2-band module (Equation 48c). Thewafer solution is to center Group 1 (or Group 2) design on the wafer chip of final width 2xthe value given by Equation 48c. The chip on the wafer should have the width required forthe 1-band use. For the 1-band use, the chip should be aligned on the module with thecenterpoint of the Group 1 or Group 2 elements centered on the module. For the 2-band use,the chip should be aligned on the module with the centerpoint of the 2-band design centeredon the module. Note that in preferred approaches, two servo readers per servo band are used.

[0400] Also shown in FIG. 23 (and FIGS. 24-25), for reference, is a tape 1204 withsections described elsewhere herein, namely edge guard bands (EGB), servo bands (SB1- SB5), data bands (DB1-DB5), and servo band guards (SBG).

[0401] FIG. 24 shows the alignment on a module of a dual-band head design with twoservo readers per band for use in a tape drive with 1-band of ^^ channels using only Group 1elements aligned at operation at far ends of operation.

[0402] FIG. 25 shows the alignment on a module of a dual-band head design with twoservo readers per band for use in a tape drive with 2-band of ^^^^ channels using bothGroup 1 and Group 2 elements aligned at operation at far ends of operation.

[0403] The dimensions of the elements and servo readers are fully defined by: ^^^.^^^^(43a or 43b), ^^^.^^^^^.^^^^(44b), ^^^.^^^^.^^^^(45b) and ^^^^^^^^^^.^^^^(46b).

[0404] For a single span head, in one approach, there are ^^ elements arranged as:^^^ , ^^^, {^^, … , ^^^}, ^^^ , ^^^.

[0405] The elements are spaced by ^^^.^^^^. The spacing: ^^^ − ^^ − ^^ and ^^^ −^^ − ^^^, are given by ^^^.^^^^.^^^^ . The spacing: ^^^ − ^^ − ^^, ^^^ − ^^ − ^^^ aregiven by ^^^.^^^^^.^^^^. The spacing: ^^^ − ^^ − ^^^ and ^^^ − ^^ − ^^^ are given by^^^^^^^^^^.^^^^.

[0406] For a dual span head, in one approach, there are two groups of ^^ elementsarranged as: ^^^ , ^^^, {^^, … , ^^^}, ^^^, ^^^, {^^^^^, … , ^^^^}, ^^^ , ^^^.

[0407] In each group, the elements are spaced by ^^^.^^^^. The spacing: ^^^ − ^^ −^^, ^^^ − ^^ − ^^^, and ^^^ − ^^ − ^^^^ are given by ^^^.^^^^.^^^^. The spacing: ^^^ −^^ − ^^, ^^^ − ^^ − ^^^, ^^^ − ^^ − ^^^^^, and ^^^ − ^^ − ^^^^ are given by^^^.^^^^^.^^^^. The spacing: ^^^ − ^^ − ^^^, ^^^ − ^^ − ^^^, ^^^ − ^^ − ^^^, and ^^^ −^^ − ^^^ are given by ^^^^^^^^^^.^^^^.

[0408] Media Specifications

[0409] To set the media specifications, one practicing the invention may define ^^^^^,^^^^^, ^^^.^^^^ (42), and ^^^^, calculate a ^^^^^^^^^^.^^^^ (41). The specifications thendefine a nominal tape width with a loose tolerance, such as 10-20 mm width dimension, orwhatever tolerances allow physically running the tape. The specification on ^^^^^^^^^^.^^^^should be tightly defined within a range that can be compensated for in terms of environmentaland aging changes, e.g., within ±1 mm. ^^^.^^^^ may then be set to be the calculated value asthe minimum, ^^^.^^^^ . ^^^ as the value in Equation 36b, and the maximum adding

[0410] Physical Chip Size for a 2-Band Design with ^^^^ elements used for both 1 and2-Band operation

[0411] The wafer used to create a head should have the width required for the 1-band use.For the 1-band use, the chip should be aligned on the module with the center of the Group 1or Group 2 elements centered on the module. For the 2-band use, the chip should be alignedon the module with the center of the 2-band design centered on the module.

[0414] Head Design Examples

[0415] This section provides examples of head designs. With a fixed media width,^^^^^, edge guard band, ^^^^^, track pitch, ^^^, writer element width ^^ and buffers,Equation 12d shows that one say to increase the capacity (e.g., by increasing ^^^^) is byincreasing the element pitch ^^^ so that more data tracks may be written in a given databand, e.g., by using previously unused guard band space on tape. Here, an evaluation ofdifferent options is explored.

[0416] Table 1, below, provides general media and head parameters common to severalillustrative designs evaluated in accordance with various approaches. Table 2 provides anevaluation of four illustrative head designs and operating points using the Equations described above. Four groups of designs are evaluated: Dn, a, b, c, d. a and b used ^^^^^of 500 mm and c and d use ^^^^^of 250 mm. a and c use Pisa angles of 0 and b and d use Pisa angles of 10 deg. D1 is a 4 DBs and 32 channels. D1 also represents a head which has 64channels spanning two DBs, i.e., 32 channels per DB. D2 and D3 use three DBs and 32 and64 channels respectively. D4 is a one DB analysis with 64 channels. All use the samenumber of elements as channels. The illustrative designs are rounded to the nearest 10 nm.

[0417] Table 2 provides the head and media parameters using the head and mediaparameters given in Table 1. Dimensions are rounded to 10 nm resolution. The choice of resolution depends on the wafer fabrication process. Five groups are studied: D1 to D5 respectively use 4, 3, 3, 1, and 1 data bands and 32, 32, 64, 64 and 128 elements (or channels). Each group uses 0 or 10 deg Pisa angle and 1 or 2 servo readers per servo band.Group D1 can also be used for a 64 element (or channel) design spanning two data bands(i.e. 32 elements per data band). Such a design would be:

[0418] {NSG1,NEG1,NSG2,NEG2,NSG3}, 49

[0419] Where NSGn represent a “group” of either 1 or 2 servo readers for 1 or 2 servoreaders per group; and NEGn represent a “group” of ^^elements with spacings given in Table 2.

[0420] In all cases, using two servo readers per servo band yields a higher capacitybecause the servo band width is narrower (close to half the size). A primary benefit of usingtwo servo readers per band, though, is to limit the transit time across the widest servopatterns to enable the use of higher angles in the servo band pattern, which in turn translatesinto more precise positioning. Note that if ^^ is fixed, the capacity may be increased byreducing ^^^(D2 versus D1). However, in the case of ^^elements split between two databands (D1 design with 2x32 elements and three groups of servo readers) versus placing all^^ elements in a single data band and reducing the number of data bands by one (D3), thecapacity is reduced. Note that the design is not affected by ^^, but the capacity bywhere ∆^^is the change in ^^from the value given in Table 2 (see Equations 12).

[0421] One note is that for a fixed ^^, the servo band width increases with a reduction in^^^and decreases with an increase in the number of servo readers per band. For servo pattern angles of 12 degrees or lower, a ^^^on the order of 100 mm is acceptable. However, for servo pattern angles of 18 to 24, a ^^^should be on the order of 50 mm.Accordingly, for D4, two servo readers per servo band yield too wide a ^^^. Therefore, adesign with 4 servo readers per servo band may be used. Such a model is not given here, buta similar approach may be used to develop the equations. D5 is a 128 element design with asingle data band where ^^^is again on the order of 50 mm with two servo readers per servo band.Table 1. General Media and Head parameters common to the designs used in Table 2 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^mm mm mm mm mm nm Nm Nm12,650 500 2.0 10.0 4 250 250 300Table 2. Comparison of design for variations in number of servo readers per band and ^^. General parameters are given in Table 1. Note the design is independent of ^^, but capacity will increase if a smaller ^^is chosen. Dimensions are rounded to 10 nm resolution. The choice of resolution depends on the wafer fabrication process. Ser vo Capacit Pisa ^^^^^^Span Span tes Rdr y Ang ^ ^ ^ Lon S on on ^ ^ ^ t s^^ ^ ^^ho^^ ^^ ^^^^^^le g rt Head Tape Per∙ ^^ ∙ ^SB D # eg # # mm mm mm mm mm mm mm # #D1 87.0 94.7 2784.4 88.4 25 3276 a0 1 4 3214 94.74 2886.88 2886.882 6 6 8 D1 88.6 96.4 2837.7 45.7 26 3328 b0 2 4 3281 52.07 2897.55 2897.556 9 0 0 D1 1 88.3 96.1 2784.4 88.4 25 3276 c0 1 4 3269 96.19 2931.43 2886.896 3 6 8 D1 1 90.0 97.8 2837.8 45.7 26 3353 d0 2 4 3258 52.85 2942.26 2897.560 6 2 6 D2 115. 123. 123.6 3708.2 117. 35 3379 a0 1 3 3288 611 3839.56 3839.562 33 2 2 D2 118. 125. 3783.9 60.5 36 3456 b0 2 3 322597 66.85 3858.48 3858.480 7 0 0 D2 1 117. 125. 125.5 3708.2 117. 35 3379 c0 1 3 3267 500 3898.80 3839.576 30 2 2 D2 1 120. 127. 3783.9 60.5 36 3456 d0 2 3 320790 67.87 3918.01 3858.494 4 0 0D3 59.1 66.8 3783.9 60.5 16 3110 a0 1 3 6425 66.85 3858.48 3858.480 7 2 4 D3 59.7 67.4 3822.9 31.3 16 3148 b0 2 3 6436 37.59 3868.23 3868.231 2 4 8 D3 1 60.0 67.8 3783.9 60.5 16 3110 c0 1 3 6447 67.87 3918.01 3858.494 4 2 4 D3 1 60.6 68.4 3822.9 31.2 16 3148 d0 2 3 6468 38.16 3927.91 3868.245 9 4 8 D4 176. 183. 183.7 11458.5 11458.5 11267. 177. 55 3532 a0 1 1 6405 77 7 0 0 01 50 2 8 D4 178. 186. 11545.1 11545.1 11440. 90.8 56 3584 b0 2 1 647648 97.107 7 34 3 0 0 D4 1 178. 186. 186.5 11635.3 11458.5 11267. 177. 55 3532 c0 1 1 6476 59 9 0 3 07 47 2 8 D4 1 181. 189. 11723.3 11545.2 11440. 90.8 56 3596 d0 2 1 645134 98.591 0 40 0 2 8 D50 1 1 1289.3 97.197.10 11545.111545.1 11440. 90.8 26 3353 a 8 8 0 7 7 34 3 2 6 D50 2 1 1290.0 97.852.76 11589.511589.5 11529. 46.4 26 3404 b 8 7 0 2 2 03 9 6 8 D5 11 1 1290.7 98.598.59 11723.311545.2 11440. 90.8 26 3379 c 0 8 6 9 1 0 40 0 4 2 D5 12 1 1291.4 99.253.56 11768.311589.5 11529. 46.4 26 3404 d 0 8 6 9 3 5 09 6 6 8

[0422] In one exemplary approach for a dual band head with two servos per servo band,exemplary parameters for a 10 degree nominal tilt angle are: ^^(= ^^) elements per band,^^^ = ^, ^^^.^^^^ = ^^. ^^ ^^, ^^^.^^^^.^^^^ = ^^. ^^ ^^, ^^^.^^^^^.^^^^ =^^. ^^ ^^, ^^^^^^^^^.^^^^ = ^^^^. ^^ ^^.

[0423] In one exemplary approach for media, exemplary parameters are: ^^^^^ =^^, ^^^ ^^, ^^^^^.^^^^ = ^^^^. ^^ ^^, ^^^ = ^ ^^^ ^^^ = ^, ^^^.^^^^ =^^. ^^ ^^ {−^, +^ ^^) with ^^^^^ = ^^^ ^^.

[0424] It will be clear that the various features of the foregoing systems and / ormethodologies may be combined in any way, creating a plurality of combinations from the descriptions presented above.

[0425] It will be further appreciated that aspects of the present invention may beprovided in the form of a service deployed on behalf of a customer to offer service on demand.

[0426] The descriptions of the various aspects of the present invention have beenpresented for purposes of illustration but are not intended to be exhaustive or limited to theapproaches disclosed. Many modifications and variations will be apparent to those ofordinary skill in the art without departing from the scope and spirit of the described approaches. The terminology used herein was chosen to best explain the principles of the present invention, the practical application or technical improvement over technologies found in the marketplace, or to enable others of ordinary skill in the art to understand theapproaches disclosed herein.

Claims

CLAIMS1. An apparatus, comprising:a magnetic head having an array of transducers, the transducers comprising dataelements, at least two first servo readers positioned toward a first end of thearray and at least two second servo readers positioned toward a second end ofthe array, wherein the array is symmetrical about a centerpoint thereof, such that a distance between a center of an innermost one of the first servo readers and a center of the data element closest thereto is the same as a distance between a center of an innermost one of the second servo readers and a center of the data element closest thereto, and such that a distance between a center of an outermost one of the first servo readers and the center of the data element closest thereto isthe same as a distance between a center of an outermost one of the secondservo readers and the center of the data element closest thereto.

2. An apparatus as recited in claim 1, wherein only two of the first servo readers andonly two of the second servo readers are present in the array.

3. An apparatus as recited in claim 2, wherein:a number of the data elements, ^^, in the array is 32, the data elements having anaverage pitch WEP.Head in a range of 86 to 97 microns,a center to center distance WSE.Short.Head between the data element closest to the firstend of the array and the first servo reader closest to the data elements is in a range of(WEP.Head / 2) + 3 to (WEP.Head / 2) + 10 microns,a center to center distance WSE.Long.Head between the data element closest to the firstend of the array and the first servo reader farthest from the data elements is in a rangeof WEP.Head + 3 to WEP.Head + 10 microns,a center to center distance between the data element closest to the second end of thearray and the second servo reader closest to the data element is about equal toWSE.Short.Head, acenter to center distance between the data element closest to the second end of thearray and the second servo reader farthest from the data element is about equal toWSE.Long.

4. An apparatus as recited in any one of the preceding claims, wherein the data elementsare write elements, wherein the magnetic head includes a second array aligned with the array in an intended direction of tape travel thereacross, the second array comprising read elements, at least two third servo readers positioned toward a first end of the second array and at least two fourth servo readers positioned toward a second end of the second array, wherein the second array is symmetrical about a centerpoint thereof.

5. An apparatus as recited in any one of the preceding claims, wherein a longitudinalaxis of the array is nominally tilted by greater than 0 degrees from normal relative to an intended direction of tape travel thereacross.

6. An apparatus as recited in any one of the preceding claims, comprising a secondarray of transducers aligned along a longitudinal axis of the array, wherein a first end of the second array is positioned adjacent the array, wherein the second array of transducers comprises second data elements and at least two third servo readerspositioned toward a second end of the second array, wherein a number of the second data elements is equal to a number of the data elements, wherein a distance between the center of the innermost second servo reader and a center of the second dataelement of the second array closest thereto is the same as the distance between thecenter of the outermost first servo reader and the center of the data element closestthereto, wherein a distance between a center of the outermost second servo reader and a center of the second data element of the second array closest thereto is the sameas the distance between the center of the innermost second servo reader and the center of the data element closest thereto.

7. An apparatus as recited in claim 6, wherein a combined array consisting of the arrayand the second array is symmetrical about a centerpoint of the combined array.

8. An apparatus as recited in any one of the preceding claims, wherein an average pitchWEP.Head of the data elements satisfies one or more of the following equations:with an accuracy of 10%, where:WTapeis a total width of a magnetic tape specified by a format for which the apparatus is designed, WEdge is a width of an edge band of the magnetic tape specified by the format,NEis a total number of data elements in the array, NDB is a number of data bands on the magnetic tape specified by the format, and^^ is a nominal tilt angle of the magnetic head relative to normal from an intendeddirection of tape travel across the magnetic head.

9. An apparatus as recited in any one of the preceding claims, wherein an average pitchWEP.Head of the data elements satisfies the following equation:^^^.^^^^with an accuracy of 2%, where: WTape is a total width of a magnetic tape specified by a format for which the apparatus is designed, WEdge is a width of an edge band of the magnetic tape specified by the format,WS is a width of a servo band of the magnetic tape specified by the format,WSBG is a width of a servo band guard of the magnetic tape specified by the format,WTP.Nom is a predefined nominal data track pitch that is in a range of greater than 0 to650 nanometers, NE is a total number of data elements in the array for performing data operations onone data band, NDB is a number of data bands on the magnetic tape specified by the format, and^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head.

10. An apparatus as recited in any one of the preceding claims, wherein a distanceWSE.Short.Head between the center of the innermost first servo reader and the center of the data element closest thereto satisfies the following equation:with an accuracy of 2%, where: WEP.Head is an average pitch of the data elements of the array, WS is a width of the servo readers in the array,WSBGis a width of a servo band guard specified by a format for which the apparatus is designed, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head.

11. An apparatus as recited in any one of the preceding claims, wherein a distanceWSE.Short.Head between the center of the innermost first servo reader and the center of the data element closest thereto satisfies the following equation:with an accuracy of 2%, where:WEP.Headis an average pitch of the data elements of the array, WSis a width of the servo readers in the array, WSBG is a width of a servo band guard specified by a format for which the apparatus is designed, WTP.Nom is a predefined nominal data track pitch that is in a range of greater than 0 to650 nanometers, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head.

12. An apparatus as recited in any one of the preceding claims, wherein a distanceWSE.Long.Head between the center of the outermost first servo reader and the center of the data element closest thereto satisfies the following equation:with an accuracy of 2%, where: WEP.Headis an average pitch of the data elements of the array, WS is a width of the servo readers in the array,WSBG is a width of a servo band guard specified by a format for which the apparatus is designed, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head.

13. An apparatus as recited in any one of the preceding claims, wherein a distancebetween the center of the outermost first servo reader and the center of the data element closest thereto satisfies the following equation:with an accuracy of 2%, where: WEP.Head is an average pitch of the data elements of the array, WS is a width of the servo readers in the array,WTP.Nom is a predefined nominal data track pitch that is in a range of greater than 0 to650 nanometers, WSBG is a width of a servo band guard specified by the format, and^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head.

14. An apparatus as recited in any one of the preceding claims, wherein a distanceWServoSpan.Head between the center of the innermost one of the first servo readers and the center of the outermost one of the second servo readers satisfies the followingequation:with an accuracy of 2%, where: NE is a total number of data elements in the array, WEP.Headis an average pitch of the data elements of the array, WS is a width of the servo readers in the array,WSBG is a width of a servo band guard specified by a format for which the apparatus is designed, and^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head.

15. An apparatus as recited in any one of the preceding claims, wherein a distanceWServoSpan.Headbetween the center of the innermost one of the first servo readers and the center of the outermost one of the second servo readers satisfies the followingequation:with an accuracy of 2%, where: NE is a total number of data elements in the array, WEP.Headis an average pitch of the data elements of the array, WS is a width of the servo readers in the array,WTP.Nom is a predefined nominal data track pitch that is in a range of greater than 0 to650 nanometers, WSBG is a width of a servo band guard specified by the format, wherein WSBG is in arange of greater than 0 to 5 microns, and ^^is a nominal tilt angle of the magnetic head relative to normal from an intended direction of tape travel across the magnetic head.

16. An apparatus as recited in any one of the preceding claims, comprising:a drive mechanism for passing a magnetic tape over the magnetic head; anda controller electrically coupled to the magnetic head.

17. An apparatus as recited in claim 16, wherein the controller is configured to notoverwrite any portions of servo bands with data tracks during writing.

18. An apparatus, comprising:a magnetic head having an array of transducers and a second array of transducers aligned along a longitudinal axis of the array, wherein a first end of the second array is positioned adjacent the array; the array comprising data elements, at least two first servo readers positioned toward a first end of the array and at least two second servo readers positioned toward a second end of the array; the second array comprising second data elements and at least two third servo readers positioned toward a second end of the second array,wherein the array is symmetrical about a centerpoint thereof, such that a distance between a center of an innermost one of the first servo readers and a center of the data element closest thereto is the same as a distance between a center ofan innermost one of the second servo readers and a center of the data element closest thereto, and such that a distance between a center of an outermost one of the first servo readers and the center of the data element closest thereto isthe same as a distance between a center of an outermost one of the secondservo readers and the center of the data element closest thereto, andwherein a distance between the center of the innermost second servo reader and a center of the data element of the second array closest thereto is the same asthe distance between the center of the outermost first servo reader and the center of the data element closest thereto, wherein a distance between a centerof the outermost second servo reader and a center of the data element of thesecond array closest thereto is the same as the distance between the center of the innermost second servo reader and the center of the data element closestthereto.

19. An apparatus as recited in claim 18, wherein only two of the first servo readers andonly two of the second servo readers are present in the array.

20. An apparatus as recited in claims 18 or 19, wherein the data elements are writeelements, wherein the magnetic head includes a third array aligned with the array in an intended direction of tape travel thereacross and a fourth array aligned with the second array in the intended direction of tape travel, the third array comprising read elements, at least two fourth servo readers positioned toward a first end of the third array and at least two fifth servo readers positioned toward a second end of the third array, wherein the third array is symmetrical about a centerpoint thereof.

21. An apparatus as recited in any one of the preceding claims 18 to 20, wherein alongitudinal axis of the array is nominally tilted by greater than 0 degrees from normal relative to an intended direction of tape travel thereacross.

22. An apparatus as recited in any one of the preceding claims 18 to 21, wherein acombined array consisting of the array and the second array is symmetrical about a centerpoint of the combined array.

23. A product, comprising:a magnetic tape having a plurality of servo bands extending along a longitudinal axis of the magnetic tape, wherein a width WSB.Tape of each of the servo bands satisfies the following equation:to an accuracy of 10%, where: WEP.Tape is an average pitch of elements on the head used to read and write data and is given as.where: ^^ is the number of elements used to write each data band,^^^is the number of databands specified by a format of the magnetic tape, WEdge is a width of an edge band of the magnetic tape where no data and no servopattern is written as specified by the format, andWTape is a width of the magnetic tape.

24. A product as recited in claim 23, wherein a pitch WServoSpan.Tape of adjacent pairs ofthe servo bands satisfies the following equation:to an accuracy of 1%, where: NE is a total number of data elements for concurrent writing per data band asspecified by a format of the magnetic tape, andWSBGis a width of a servo band guard, wherein WSBGis in a range of greater than 0 to 5 microns.

25. A product as recited in claims 23 or 24, wherein a pitch WServoSpan.Tape of adjacentpairs of the servo bands satisfies the following equation:with an accuracy of 1%, where WEP.Tape is an average pitch of elements on the head used to read and write data and is given as:WSE.Short.Tape is a design pitch, specified by a format of the magnetic tape, between adata element closest to a first end of an array and a servo reader of the array locatedclosest to the data element, and is given by:WSE.Long.Tapeis a design pitch, specified by a format of the magnetic tape, between thedata element closest to the first end of the array and a second servo reader of thearray located closest to the first end, and is given by: ^^^.^^^^^.^^^^~^^^.^^^^where: NEis a total number of data elements for concurrent writing specified by a format of the magnetic tape, and NDB is a total number of data bands on the tape specified by a format of the magnetic tape, and WTapeis the width of the tape and specified by a format of the magnetic tape, and WEdge is the edge guard band of the tape and specified by a format of the magnetic tape as the region on the tape where no data or servo pattern is written.

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