Disk device and method for writing spiral pattern

Abstract

A magnetic disk device and a method for writing a spiral pattern are provided that can improve reliability. The magnetic disk device of this embodiment includes: a disk having a first surface and a second surface different from the first surface; a first head for reading and writing data from and to the first surface; a second head for reading and writing data from and to the second surface; a voice coil motor for moving the first and second heads; and a controller for dividing and writing multiple spiral patterns to be written to one surface of the disk onto the first and second surfaces.

Description

[0001] Related Application

[0002] This application claims priority from Japanese Patent Application No. 2021-151330 (filing date: September 16, 2021), the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments of the present invention relate to a magnetic disk device and a method for writing a spiral pattern. Background Art

[0004] During the initial process of blank disc lighting (BDW), a magnetic disk drive writes multiple spiral servo patterns (hereinafter sometimes referred to as course guide spiral (CGS) servo patterns) onto a single disc surface where no data or patterns have been written. If two adjacent CGS servo patterns within a single disc surface are adjacent to or intersect with each other, data written to the adjacent or intersecting portion of the servo patterns is erased. Consequently, the magnetic disk drive may be unable to track or perform seek operations in the adjacent or intersecting portion of the disc surface. Summary of the Invention

[0005] The technical problem to be solved by the embodiments of the present invention is to provide a magnetic disk device and a method for writing a spiral pattern that can improve reliability.

[0006] The magnetic disk device of this embodiment comprises: a disk having a first surface and a second surface different from the first surface; a first head for reading and writing data on the first surface; a second head for reading and writing data on the second surface; a voice coil motor for moving the first head and the second head; and a controller for dividing and writing a plurality of spiral patterns to be written to one surface of the disk onto the first surface and the second surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a block diagram showing the configuration of the magnetic disk device according to the first embodiment.

[0008] Figure 2 This is a schematic diagram showing an example of the arrangement of the head relative to the disk according to the first embodiment.

[0009] Figure 3This is a plan view schematically showing an example of a virtual plane through which a plurality of disks are stacked and viewed from above (perspective) according to the first embodiment.

[0010] Figure 4 It is a plan view schematically showing an example of the arrangement of CGS servo patterns on a plurality of planes according to the first embodiment.

[0011] Figure 5 It is a plan view schematically showing an example of the arrangement of CGS servo patterns on a surface according to the first embodiment.

[0012] Figure 6 It is a plan view schematically showing an example of the arrangement of CGS servo patterns on a plurality of planes according to the first embodiment.

[0013] Figure 7 It is a plan view schematically showing an example of the arrangement of FGS servo patterns on a surface according to the first embodiment.

[0014] Figure 8 It is a plan view schematically showing an example of the arrangement of FS servo patterns on each surface according to the first embodiment.

[0015] Figure 9 This is a schematic diagram showing an example of the arrangement of the CGS servo pattern according to the first embodiment.

[0016] Figure 10 This is a schematic diagram showing an example of the arrangement of the CGS servo pattern according to the first embodiment.

[0017] Figure 11 This is a schematic diagram showing an example of the arrangement of the CGS servo pattern according to the first embodiment.

[0018] Figure 12 It is a schematic diagram showing an example of a method for writing and a method for reading a CGS servo pattern according to the first embodiment.

[0019] Figure 13 This is a schematic diagram showing an example of a method for reading a plurality of CGS servo patterns written on different surfaces when the virtual CGS interval is smaller than the switchable interval according to the first embodiment.

[0020] Figure 14 This is a schematic diagram showing an example of a method for setting a non-switchable area according to the first embodiment.

[0021] Figure 15 This is a schematic diagram showing an example of a method for setting a non-switchable area according to the first embodiment.

[0022] Figure 16 This is a schematic diagram showing an example of a change in the switchable interval according to the first embodiment.

[0023] Figure 17 This is a schematic diagram showing an example of measuring the actual CGS interval corresponding to the odd-numbered CGS servo pattern written on the surface according to the first embodiment.

[0024] Figure 18 This is a schematic diagram showing an example of measuring an even-numbered actual CGS interval corresponding to an even-numbered CGS servo pattern written on the back surface according to the first embodiment.

[0025] Figure 19 It is a table Figure 17 The actual CGS interval is different from Figure 18 Schematic diagram of an example of the synthesis of the actual CGS interval.

[0026] Figure 20 This is a schematic diagram showing an example of the measurement results of the change in RRO in the first embodiment.

[0027] Figure 21 This is a flowchart showing an example of BDW according to the first embodiment.

[0028] Figure 22 This is a block diagram showing the configuration of a magnetic disk device according to Modification 1. DETAILED DESCRIPTION

[0029] Hereinafter, embodiments will be described with reference to the accompanying drawings. However, the accompanying drawings are merely examples and do not limit the scope of the invention.

[0030] (First embodiment)

[0031] Figure 1 This is a block diagram showing the configuration of the magnetic disk device 1 according to the first embodiment.

[0032] The magnetic disk drive 1 includes a head disk assembly (HDA) (described later), a driver IC 20, a head amplifier integrated circuit (hereinafter referred to as a head amplifier IC or preamplifier) 30, a volatile memory 70, a nonvolatile memory 80, a buffer memory (cache) 90, and a system controller 130, which is a single-chip integrated circuit. Furthermore, the magnetic disk drive 1 is connected to a host system (hereinafter referred to simply as a host) 100.

[0033] The HAD includes a magnetic disk (hereinafter referred to as a disk) 10, a spindle motor (hereinafter referred to as an SPM) 12, an arm 13 carrying a head 15, and a voice coil motor (hereinafter referred to as a VCM) 14. The disk 10 is mounted on the SPM 12 and rotated by the SPM 12. The arm 13 and the VCM 14 constitute an actuator. Driven by the VCM 14, the actuator controls the movement of the head 15 mounted on the arm 13 to a predetermined position on the disk 10. Multiple disks 10 and multiple heads 15 are provided. Alternatively, only one disk 10 and one head 15 may be provided.

[0034] The disk 10 has a data-writeable area divided into: a user data area 10a accessible to the user; a media cache (sometimes referred to as a media cache area or storage area) 10b, which temporarily stores or records data (or commands) transmitted from a host, etc., before writing them to a predetermined area within the user data area 10a; and a system area 10c, where information required for system management is stored. Hereinafter, the direction from the inner circumference to the outer circumference of the disk 10, or from the outer circumference to the inner circumference, is referred to as the radial direction. The direction from the inner circumference to the outer circumference in the radial direction is referred to as the outer direction (outer direction), and the direction from the outer circumference to the inner circumference is referred to as the inner direction (inner direction). The direction perpendicular to the radial direction of the disk 10 is referred to as the circumferential direction. The circumferential direction corresponds to the direction along the circumference of the disk 10. The radial and circumferential directions are orthogonal to each other. Predetermined positions in the radial direction of the disk 10 are sometimes referred to as radial positions, while predetermined positions in the circumferential direction of the disk 10 are sometimes referred to as circumferential positions. Radial positions and circumferential positions are sometimes collectively referred to as simply positions. The disk 10 can be divided into multiple areas. For example, the disk 10 can be divided into areas (hereinafter sometimes referred to as zones) each including a predetermined number of tracks in the radial direction. A zone can be divided into areas in the radial direction for each track.

[0035] In addition, a “track” refers to a recording area in a plurality of recording areas obtained by dividing the disk 10 in a radial direction, a recording area in one circle at a predetermined radial position of the disk 10, a predetermined recording area at a predetermined radial position of the disk 10, a recording area extending in the circumferential direction of the disk 10, a recording area corresponding to the path of the head 15 positioned at a predetermined radial position of the disk 10, a path of the head 15 positioned at a predetermined radial position of the disk 10, data written to a recording area in a plurality of recording areas obtained by dividing the disk 10 in a radial direction, and a recording area in one circle at a predetermined radial position of the disk 10. The term "data area", data written to a predetermined recording area at a predetermined radial position of the disk 10, data written to a recording area extending in the circumferential direction of the disk 10, data written to a recording area equivalent to the path of the head 15 positioned at a predetermined radial position of the disk 10, data written along the path of the head 15 positioned at a predetermined radial position of the disk 10, data extending in the circumferential direction of the disk 10, data written to a predetermined track of the disk 10, data written to one week of a predetermined track of the disk 10, a part of data written to a predetermined track of the disk 10, or other various meanings. The term "sector" can be used to refer to one of the multiple recording areas formed by circumferentially dividing a predetermined track of the disk 10, one of the multiple recording areas formed by dividing a recording area extending circumferentially at a predetermined radial position on the disk 10, a predetermined recording area of a predetermined track on the disk 10, a predetermined circumferential position of a predetermined track on the disk 10, a predetermined circumferential position (predetermined position) at a predetermined radial position on the disk 10, data written to one of the multiple recording areas formed by circumferentially dividing a predetermined track on the disk 10, data written to one of the multiple recording areas formed by dividing a recording area extending circumferentially at a predetermined radial position on the disk 10, data written to a predetermined recording area of a predetermined track on the disk 10, data written to a predetermined circumferential position of a predetermined track on the disk 10, data written to a predetermined circumferential position (predetermined position) at a predetermined radial position on the disk 10, data written to a predetermined sector, or various other meanings. The "radial width of a track" may also be referred to as the "track width." “A path passing through the center position of the track width in a predetermined track” may be referred to as “track center.” Data that can be used by a user and written to the user data area 10 a may be referred to as user data.

[0036] The head 15 faces the disk 10. For example, one head 15 faces one surface of the disk 10. The head 15 is mainly composed of a slider, and includes a write head 15W and a read head 15R attached to the slider. The write head 15W writes data to the disk 10. The read head 15R reads the data written to the disk 10. In addition, the "write head 15W" is sometimes referred to as simply the "head 15," the "read head 15R" is sometimes referred to as simply the "head 15," or the "write head 15W and read head 15R" are sometimes collectively referred to as the "head 15." The "center of the head 15" is sometimes referred to as the "head 15," the "center of the write head 15W" is sometimes referred to as the "write head 15W," and the "center of the read head 15R" is sometimes referred to as the "read head 15R." The "center of the write head 15W" is sometimes referred to as simply the "head 15," and the "center of the read head 15R" is sometimes referred to as simply the "head 15." The phrase “positioning the center of the head 15 at the center of a predetermined track” may be expressed as “positioning the head 15 at the predetermined track”, “arranging the head 15 at the predetermined track”, or “locating the head 15 at the predetermined track”.

[0037] Figure 2 1 is a schematic diagram showing an example of the configuration of the head 15 relative to the disk 10 of this embodiment. Figure 2 As shown, in the circumferential direction, the rotation direction of the disk 10 is referred to as the rotation direction. Figure 2 In the example shown, the direction of rotation is expressed as counterclockwise, but it can also be the opposite direction (clockwise). The height direction Z is a direction parallel to the direction in which the main axis SP of the SPM12 extends. In other words, the height direction Z is the direction in which the multiple disks 10 are stacked. In addition, the height direction Z is equivalent to the direction from the bottom wall of the magnetic disk device 1 toward the cover opposite to the bottom wall. In the height direction Z, the direction from disk 10-1 toward disk 10-0 is sometimes called the upper side (or just the upper side), and the direction from disk 10-0 toward disk 10-1 is sometimes called the lower side (or just the lower side). In addition, assuming that there is an observation position for observing the magnetic disk device 1 on the front end side of the arrow indicating the height direction Z, the situation of observing the surface of the disk 10 from this observation position is sometimes called a top view.

[0038] exist Figure 2 In the example shown, the SPM 12 has a main axis SP. The main axis SP extends in the height direction Z.

[0039] exist Figure 2In the example shown, disk 10 includes disks 10-0, 10-1, ... Disk 10 is mounted on a spindle SP. Disk 10 has surfaces 10S (10S0, 10S1, 10S2, 10S3, ...). Surfaces 10S (10S0, 10S1, 10S2, 10S3, ...) extend parallel to a plane extending perpendicular to the height direction Z. Furthermore, surfaces 10S (10S0, 10S1, 10S2, 10S3, ...) may extend parallel to a plane that is tilted relative to the plane extending perpendicular to the height direction Z. Disk 10-0 has a surface 10S0 and a back surface 10S1 opposite to surface 10S0. Surface 10S0 faces upward in the height direction Z. Back surface 10S1 faces downward in the height direction Z. Back surface 10S1 is located below surface 10S0. Disk 10-1 has a surface 10S2 and a back surface 10S3 opposite to surface 10S2. Surface 10S2 faces upward in the height direction Z. Surface 10S2 is opposite back surface 10S1. Back surface 10S3 faces downward in the height direction Z. Back surface 10S3 is located below surface 10S2. Disk 10-1 is located below disk 10-0. When viewed from above, disks 10-0 and 10-1 overlap. Surface 10S0 has a user data area 10a0 and a system area 10b0. Back surface 10S1 has a user data area 10a1 and a system area 10b1. Surface 10S2 has a user data area 10a2 and a system area 10b2. Back surface 10S3 has a user data area 10a3 and a system area 10b3.

[0040] Header 15 includes multiple headers 15. Figure 2 In the example shown, the heads 15 include: head 15-0, head 15-1, head 15-2, head 15-3, .... The heads 15 face the surface 10S. The plurality of heads 15 face the surfaces 10S of the plurality of disks 10, respectively. Figure 2 In the example shown, head 15-0 faces surface 10S0. Head 15-0 writes data to and reads data from surface 10S0. Head 15-1 faces back surface 10S1. Head 15-1 writes data to and reads data from back surface 10S1. Head 15-2 faces surface 10S2. Head 15-2 writes data to and reads data from back surface 10S2. Head 15-3 faces back surface 10S3. Head 15-3 writes data to and reads data from back surface 10S3. Five or more heads 15 may be provided, and two or more disks 10 may be provided.

[0041] Figure 3 This is a plan view schematically showing an example of an imaginary surface of the disks 10 when a plurality of disks 10 according to the present embodiment are stacked and viewed from above (see through). Figure 3A surface (hereinafter sometimes referred to as a virtual surface) 10S of a disk 10 is shown as viewed from above (or from above) in the height direction Z through multiple surfaces 10S (10S0, 10S1, 10S2, and 10S3) of a plurality of overlapping disks 10. A virtual surface corresponds to a surface of the disk 10 that is displayed as if data and graphics on other surfaces that are not actually present on the same surface are present on the same surface when the plurality of overlapping disks 10 are viewed from above. Hereinafter, "a virtual surface of the disk 10 viewed from above (through) a predetermined surface of the disk 10 and other surfaces different from the predetermined surface" may also be referred to as "a virtual surface of the predetermined surface and other surfaces." Figure 3 Only the configuration necessary for explanation is shown. Figure 3 The innermost periphery IMC and the outermost periphery OMC of the disc 10 are shown.

[0042] The imaginary surface 10S of the disk 10 has: a plurality of servo patterns (hereinafter sometimes referred to as product servo patterns) or a plurality of servo areas (hereinafter sometimes referred to as product servo areas) PSV used in the final product, a plurality of final spiral (FS) servo patterns FSS, a plurality of fine guide spiral (FGS) servo patterns FGSS, and a plurality of course guide spiral (CGS) servo patterns CGSS. Figure 3 In the figure, the FS servo pattern FSS and the CGS servo pattern CGSS are described as extending in parallel for convenience of explanation. However, they do not need to extend in parallel in practice. Since the direction and / or speed of writing the FS servo pattern FSS, the FGS servo pattern FGSS, and the CGS servo pattern CGSS are arbitrary, the FS servo pattern FSS, the FGS servo pattern FGSS, and the CGS servo pattern CGSS are basically not parallel.

[0043] exist Figure 3 In the figure, the product servo pattern PSV is shown as a rectangular shape extending linearly in the radial direction. Multiple product servo patterns PSV extend radially in the radial direction of the disk 10 and are discretely arranged at predetermined intervals in the circumferential direction of the disk 10. Furthermore, the product servo pattern PSV is described as extending linearly from the inside to the outside in the radial direction, but it can also be curved. For example, the product servo pattern PSV can also be arranged spirally from the inside to the outside in the radial direction. Hereinafter, a product servo pattern PSV on a predetermined track may sometimes be referred to as a "product servo sector." Furthermore, a product servo pattern may sometimes be referred to as a product servo sector. A "product servo sector" may sometimes be referred to as a "product servo pattern." A product servo sector contains product servo data. Furthermore, "product servo data written to a product servo sector" may sometimes be referred to as a "product servo sector." Furthermore, data other than the product servo data written to the user data area 10a outside the product servo sector may sometimes be referred to as user data.

[0044] A servo sector includes servo data, such as a preamble, a servo mark, a Gray code, a PAD, pulse train data, and a post code. Furthermore, a servo sector (or servo data) may not include a post code. A servo sector (or servo data) may also be configured to include at least one of the following: a preamble, a servo mark, a Gray code, a PAD, pulse train data, and a post code. Furthermore, a servo sector (or servo data) may also be configured to include data other than a preamble, a servo mark, a Gray code, a PAD, pulse train data, and a post code. In a servo sector, the preamble, servo mark, Gray code, a PAD, pulse train data, and a post code are arranged continuously from front to back in the aforementioned order in the circumferential direction. The preamble includes preamble information for synchronizing with a reproduced signal of a servo pattern composed of servo marks, Gray code, etc. The servo mark includes servo mark information indicating the start of the servo pattern. Gray code consists of the address of a predetermined track (cylinder address) and the address of a servo sector of the predetermined track. Burst data is data (relative position data) used to detect the radial and / or circumferential positional offset (position error) of the head 15 relative to the track center of the predetermined track. It consists of a repetitive pattern of a predetermined period. The PAD includes gap information and PAD information for synchronization signals such as servo AGC. Burst data is written as a data pattern in which the phase of the burst data in the radial direction of the disk 10 is reversed 180° per servo track period. A servo track (servo cylinder) corresponds to a track that is the target of a write or read operation based on a command from the host 100 or the like. Burst data is used, for example, to determine the radial and / or circumferential position of the head 15 on the disk 10 (hereinafter sometimes referred to as the head position). Burst data includes, for example, an N-burst and a Q-burst. The N-burst and Q-burst are written as data patterns with a 90° phase shift relative to each other in the radial direction of the disk 10. The power-on self-test code includes data (hereinafter sometimes referred to as RRO correction data) for correcting errors caused by jitter (repeatable runout: RRO) synchronized with the rotation of disk 10 when writing servo data to the disk, resulting from deformation of the track relative to a target path (hereinafter sometimes referred to as the target path) of head 15 arranged concentrically with disk 10, such as the center of the track. For ease of explanation, errors caused by deformation of the track relative to the target path due to RRO may be referred to simply as RRO.

[0045] exist Figure 3In the figure, the FS servo pattern FSS is indicated by a two-dot chain line. Multiple FS servo patterns FSS extend spirally from the inside to the outside in the radial direction of the disk 10 and are discretely arranged at predetermined intervals in the circumferential direction of the disk 10. Hereinafter, a FS servo pattern in a predetermined track may be referred to as a "FS servo sector." Furthermore, a FS servo pattern may also be referred to as a FS servo sector. A "FS servo sector" may also be referred to as a "FS servo pattern." An FS servo sector contains corresponding servo data. Furthermore, "FS servo data corresponding to an FS servo sector written to an FS servo sector" may also be referred to as an "FS servo sector."

[0046] exist Figure 3 In the figure, the FGS servo pattern FGSS is indicated by a single-dot chain line. Multiple FGS servo patterns FGSS extend spirally from the inside to the outside in the radial direction of the disk 10 and are discretely arranged at predetermined intervals in the circumferential direction of the disk 10. For example, the stroke of the FGS servo pattern FGSS that allows positioning control from the inside to the outside in the radial direction is longer than the stroke of the FS servo pattern FSS that allows positioning control from the inside to the outside in the radial direction. The number of FGS servo patterns FGSS on a single surface of the disk 10 is less than the number of FS servo patterns FSS. For example, the number of FGS servo patterns FGSS on a single surface of the disk 10 is 32. The number of FS servo patterns FSS on a single surface of the disk 10 is 200 to 300. The frequency corresponding to the FGS servo pattern FGSS is different from the frequency corresponding to the FS servo pattern FSS and the frequency corresponding to the product servo pattern PSV. Hereinafter, a single FGS servo pattern on a predetermined track may also be referred to as an "FGS servo sector." Furthermore, an FGS servo pattern is sometimes referred to as an FGS servo sector. An "FGS servo sector" is sometimes referred to as an "FGS servo pattern." An FGS servo sector includes corresponding servo data. Furthermore, "FGS servo data corresponding to an FS servo sector written within an FGS servo sector" is sometimes referred to as an "FGS servo sector."

[0047] exist Figure 3In the figure, the CGS servo pattern CGSS is shown by dotted lines. Multiple CGS servo patterns CGSS extend spirally from the inside to the outside in the radial direction of the disk 10 and are discretely arranged at predetermined intervals in the circumferential direction of the disk 10. For example, the stroke from the inside to the outside in the radial direction of the CGS servo pattern CGSS that can be positioned is longer than the stroke from the inside to the outside in the radial direction of the FGS servo pattern FGSS that can be positioned. On the disk 10, the number of CGS servo patterns CGSS is less than the number of FGS servo patterns FGSS. On one surface of the disk 10, the number of CGS servo patterns CGSS is, for example, ten. The frequency corresponding to the CGS servo pattern CGSS is different from the frequency corresponding to the FGS servo pattern FGSS, the frequency corresponding to the FS servo pattern FSS, and the frequency corresponding to the product servo pattern PSV. Hereinafter, a CGS servo pattern CGSS on a predetermined track may sometimes be referred to as a "CGS servo sector." Furthermore, a CGS servo pattern may sometimes be referred to as a CGS servo sector. A "CGS servo sector" is sometimes referred to as a "CGS servo pattern." A CGS servo sector includes corresponding servo data. Furthermore, "servo data corresponding to a CGS servo sector written in a CGS servo sector" is sometimes referred to as a "CGS servo sector."

[0048] Figure 4 It is a plan view schematically showing an example of arrangement of CGS servo patterns CGSS on a plurality of surfaces 10S according to the present embodiment. Figure 4 The imaginary surfaces of the front surface 10S0 and the back surface 10S1 of the disk 10 - 0 are shown. Figure 4 Only the configuration necessary for explanation is shown. Alternatively, a product servo pattern PSV, a plurality of FS servo patterns FSS, and a plurality of FGS servo patterns FGSS may be arranged on the front surface 10S0 and the back surface 10S1 of the disc 10 - 0 .

[0049] A plurality of CGS servo patterns CGSS are arranged within a plurality of surfaces 10S. Figure 4In the example shown, the plurality of CGS servo patterns CGSS include CGS servo patterns CGSS2n+1, CGSS2n+2, CGSS2n+3, CGSS2n+4, CGSS2n+5, CGSS2n+6, CGSS2n+7, CGSS2n+8, CGSS2n+9, and CGSS2n+10. N is an integer greater than or equal to 0. The CGS servo patterns CGSS2n+1, CGSS2n+2, CGSS2n+3, CGSS2n+4, CGSS2n+5, CGSS2n+6, CGSS2n+7, CGSS2n+8, CGSS2n+9, and CGSS2n+10 are arranged in the order shown in the circumferential direction clockwise (clockwise). Hereinafter, the odd-numbered CGS servo patterns CGSS2n+1, CGSS2n+3, CGSS2n+5, CGSS2n+7, and CGSS2n+9, counted clockwise (clockwise) from a predetermined CGS servo pattern CGSS, for example, CGS servo pattern CGSS2n+1, may be referred to as “odd-numbered CGS servo patterns.” The even-numbered CGS servo patterns CGSS2n+2, CGSS2n+4, CGSS2n+6, CGSS2n+8, and CGSS2n+10, counted clockwise (clockwise) from a predetermined CGS servo pattern CGSS, for example, CGS servo pattern CGSS2n+1, may be referred to as “even-numbered CGS servo patterns.”

[0050] Multiple CGS servo patterns CGSS2n+1 to CGSS2n+10 are arranged on the front surface 10S0 and back surface 10S1 of the disk 10-0. The CGS servo patterns CGSS2n+1, CGSS2n+2, CGSS2n+3, CGSS2n+4, CGSS2n+5, CGSS2n+6, CGSS2n+7, CGSS2n+8, CGSS2n+9, and CGSS2n+10 are arranged in the order listed, spaced apart, in a clockwise (clockwise) direction along the circumference when viewed from above. When viewed from above, the multiple CGS servo patterns CGSS2n+1 to CGSS2n+10 do not overlap at the innermost circumference IMC and the outermost circumference OMC. For example, when viewed from above, the multiple CGS servo patterns CGSS2n+1 to CGSS2n+10 can be arranged at equal intervals at the innermost circumference IMC. Furthermore, when viewed from above, the multiple CGS servo patterns CGSS2n+1 to CGSS2n+10 do not need to be arranged at equal intervals on the innermost circumference IMC. The multiple CGS servo patterns CGSS2n+1 to CGSS2n+10 may also be arranged across three or more surfaces of the disk 10. The multiple CGS servo patterns CGSS2n+1 to CGSS2n+10 may also be arranged similarly on the front surface 10S0 and back surface 10S1 of the disk 10-0 and on the front surface 10S2 and back surface 10S3 of the disk 10-1. Furthermore, the multiple CGS servo patterns CGSS2n+1 to CGSS2n+10 may also be arranged on at least one of the front surface 10S0, back surface 10S1, front surface 20S2, and back surface 10S3.

[0051] Figure 5 It is a plan view schematically showing an example of the arrangement of the CGS servo pattern CGSS on the surface 10S0 of this embodiment. Figure 5 The virtual surface of the disk 10 obtained by viewing the surface 10S0 of the disk 10 - 0 from above in the height direction Z is shown. Figure 5 Only the configuration necessary for explanation is shown.

[0052] exist Figure 5In the example shown, on surface 10S0 of disk 10-0, odd-numbered CGS servo patterns CGSS2n+1, CGSS2n+3, CGSS2n+5, CGSS2n+7, and CGSS2n+9 are arranged in the order shown in the circumferential direction clockwise (clockwise). For example, odd-numbered CGS servo patterns CGSS2n+1, CGSS2n+3, CGSS2n+5, CGSS2n+7, and CGSS2n+9 are arranged from the innermost circumference IMC to the outermost circumference OMC. Alternatively, odd-numbered CGS servo patterns CGSS2n+1, CGSS2n+3, CGSS2n+5, CGSS2n+7, and CGSS2n+9 may not be arranged from the innermost circumference IMC to the outermost circumference OMC. In addition, the odd-numbered CGS servo patterns CGSS2n+1, CGSS2n+3, CGSS2n+5, CGSS2n+7, and CGSS2n+9 may be arranged on at least one of the rear surface 10S1, the front surface 20S2, and the rear surface 10S3.

[0053] Figure 6 It is a plan view schematically showing an example of the arrangement of CGS servo patterns CGSS on a plurality of surfaces 10S1 according to the present embodiment. Figure 6 The virtual surface of the disk 10 obtained by viewing through the surface 10S1 of the disk 10 - 0 from above in the height direction Z is shown. Figure 6 Only the configuration necessary for explanation is shown.

[0054] exist Figure 6In the example shown, on surface 10S1 of disk 10-0, even-numbered CGS servo patterns CGSS2n+2, CGSS2n+4, CGSS2n+6, CGSS2n+8, and CGSS2n+10 are arranged in the order shown in the circumferential direction clockwise (clockwise). When viewed from above, the even-numbered CGS servo patterns CGSS2n+2, CGSS2n+4, CGSS2n+6, CGSS2n+8, and CGSS2n+10 are arranged so as not to overlap with the odd-numbered CGS servo patterns CGSS2n+1, CGSS2n+3, CGSS2n+5, CGSS2n+7, and CGSS2n+9. For example, the even-numbered CGS servo patterns CGSS2n+2, CGSS2n+4, CGSS2n+6, CGSS2n+8, and CGSS2n+10 are arranged from the innermost circumference IMC to the outermost circumference OMC. Furthermore, the even-numbered CGS servo patterns CGSS2n+2, CGSS2n+4, CGSS2n+6, CGSS2n+8, and CGSS2n+10 do not need to be arranged within the range from the innermost circumference IMC to the outermost circumference OMC. Furthermore, the even-numbered CGS servo patterns CGSS2n+2, CGSS2n+4, CGSS2n+6, CGSS2n+8, and CGSS2n+10 may be arranged on at least one of the back surface 10S1, the front surface 20S2, and the back surface 10S3.

[0055] Figure 7 It is a plan view schematically showing an example of the arrangement of the FGS servo pattern FGSS on the surface 10S1 of the present embodiment. Figure 7 The surface of the disk 10 as viewed from above in the height direction Z, that is, the surface 10S2 of the disk 10 - 1 , is shown. Figure 7 A radial position ORP0 located inside the outermost periphery OMC and a radial position IRP0 located between the radial position ORP0 and the innermost periphery IMC are shown. Figure 7 Only the configuration necessary for explanation is shown. In addition, a product servo pattern PSV and / or a plurality of FS servo patterns FSS may be arranged on the surface 10S2 of the disc 10-1.

[0056] exist Figure 7 In the example shown, multiple FGS servo patterns FGSS are arranged on the surface 10S2 of the disk 10-1. For example, the multiple FGS servo patterns FGSS are arranged within the range from the radial position IRP0 to the radial position ORP0. Alternatively, the multiple FGS servo patterns FGSS may be arranged within the range from the innermost periphery IMC to the outermost periphery OMC. Furthermore, the multiple FGS servo patterns FGSS may be arranged on at least one of the back surface 10S1, the front surface 20S2, and the back surface 10S3.

[0057] Figure 8 It is a plan view schematically showing an example of the arrangement of the FS servo patterns FSS on the surfaces 10S0 , 10S1 , 10S2 , and 10S3 according to the present embodiment. Figure 8 The surface of the disk 10 viewed from above in the height direction Z is shown. Figure 8 A radial position ORP1 located inside the radial position ORP0 and a radial position IRP1 located between the radial position ORP1 and the radial position IRP0 are shown. Figure 8 Only the configuration necessary for explanation is shown. In addition, product servo patterns PSV may be arranged on the front surface 10S0, back surface 10S1, front surface 10S2, and back surface 10S3 of the disks 10-0 and 10-1.

[0058] exist Figure 8 In the example shown, multiple FS servo patterns FSS are arranged on each of the surface 10S0, back surface 10S1, surface 10S2, and back surface 10S3 of disks 10-0 and 10-1. For example, the multiple FS servo patterns FSS are arranged within the range from radial position IRP1 to radial position ORP1. Alternatively, the multiple FS servo patterns FSS may be arranged within the range from the innermost periphery IMC to the outermost periphery OMC. Furthermore, the multiple FS servo patterns FSS may be arranged on at least one of the surface 10S0, back surface 10S1, surface 10S2, and back surface 10S3.

[0059] The driver IC 20 is connected to the system controller 130 (more specifically, the MPU 60 described later), the SPM 12 , and the VCM 14 , and controls driving of the SPM 12 and the VCM 14 under the control of the system controller 130 (more specifically, the MPU 60 described later).

[0060] The head amplifier IC (preamplifier) 30 includes a read amplifier and a write driver (not shown). The read amplifier amplifies the read signal from the disk 10 and outputs it to the system controller 130 (specifically, the read / write (R / W) channel 40 described later). The write driver outputs a write current to the head 15 in response to the signal output from the R / W channel 40.

[0061] The volatile memory 70 is a semiconductor memory that loses stored data if power is cut off. The volatile memory 70 stores data required for processing by various components of the magnetic disk drive 1. Examples of the volatile memory 70 include DRAM (Dynamic Random Access Memory) and SDRAM (Synchronous Dynamic Random Access Memory).

[0062] The nonvolatile memory 80 is a semiconductor memory that records stored data even when power is cut off. The nonvolatile memory 80 is, for example, a NOR-type or NAND-type flash ROM (Flash Read Only Memory: FROM).

[0063] The buffer memory 90 is a semiconductor memory that temporarily stores data exchanged between the magnetic disk device 1 and the host computer 100. Alternatively, the buffer memory 90 may be integrally formed with the volatile memory 70. The buffer memory 90 may be, for example, a DRAM, an SRAM (Static Random Access Memory), an SDRAM, a FeRAM (Ferroelectric Random Access Memory), or an MRAM (Magnetoresistive Random Access Memory).

[0064] The system controller (controller) 130 is implemented, for example, using a large-scale integrated circuit (LSI) known as a system-on-a-chip (SoC), in which multiple components are integrated into a single chip. The system controller 130 includes a read / write (R / W) channel 40, a hard disk controller (HDC) 50, and a microprocessor (MPU) 60. The R / W channel 40, HDC 50, and MPU 60 are electrically connected to one another. The system controller 130 is also electrically connected to, for example, the driver IC 20, the head amplifier IC 60, the volatile memory 70, the nonvolatile memory 80, the buffer memory 90, and the host system 100.

[0065] The R / W channel 40 performs signal processing for data transferred from the disk 10 to the host 100, such as read data, and for data transferred from the host 100, such as write data, based on instructions from the MPU 60 (described later). The R / W channel 40 is electrically connected to, for example, the head amplifier IC 30, the HDC 50, and the MPU 60. The R / W channel 40 includes circuitry or functions for modulating write data. Furthermore, the R / W channel 40 includes circuitry or functions for measuring the signal quality of read data and decoding read data.

[0066] The HDC 50 controls data transfer between the host 100 and the R / W channel 40 according to instructions from the MPU 60 described later. The HDC 50 is electrically connected to the R / W channel 40, the MPU 60, the volatile memory 70, the nonvolatile memory 80, and the buffer memory 90, for example.

[0067] The MPU 60 is a main controller that controls various components of the magnetic disk drive 1. The MPU 60 controls the VCM 14 via the driver IC 20, performing servo control to position the head 15. The MPU 60 controls writing data to the disk 10 and selects the storage destination for data transmitted from the host 100, such as the write data. The MPU 60 controls reading data from the disk 10 and controls the processing of data transmitted from the disk 10 to the host 100, such as read data. Furthermore, the MPU 60 manages the area where data is recorded. The MPU 60 is connected to various components of the magnetic disk drive 1. For example, the MPU 60 is electrically connected to the driver IC 20, the R / W channel 40, and the HDC 50.

[0068] The MPU 60 includes a read / write control unit 610, a CGS servo pattern control unit 620, a measurement unit 630, a servo pattern control unit 640, and a positioning control unit 650. The MPU 60 executes the processing of each of these units, such as the read / write control unit 610, the CGS servo pattern control unit 620, the measurement unit 630, the servo pattern control unit 640, and the positioning control unit 650, in firmware. Alternatively, the MPU 60 may include each of these units, such as the read / write control unit 610, the CGS servo pattern control unit 620, the measurement unit 630, the servo pattern control unit 640, and the positioning control unit 650, as circuits.

[0069] The read / write control unit 610 controls data reading and writing according to commands from the host computer 100. The read / write control unit 610 controls the VCM 14 via the driver IC 20 to position the head 15 at a predetermined radial position on the disk 10 and execute the read or write process. Hereinafter, "write process" and "read process" may be collectively referred to as "access" or "access process."

[0070] The CGS servo pattern control unit 620 writes a CGS servo pattern CGSS onto the disk 10. As the initial step of blank disk writing (BDW) (or blank disk servo writing), in which the CGS servo pattern CGSS, the FGS servo pattern FGSS, and the FS servo pattern FSS are sequentially written onto a disk 10 that has no data or patterns written thereon (hereinafter sometimes referred to as a blank state), the CGS servo pattern control unit 620 performs stroke calibration on the disk 10 and writes the CGS servo pattern CGSS onto the disk 10. Since the servo pattern control unit 620 cannot read data or patterns from a blank disk 10, it does not perform a read process (or track). Instead, it uses the position of disk 10 corresponding to a reference clock of the blank disk 10 (hereinafter sometimes referred to as the clock reference position) as the starting point. Based on information about the velocity of the head 15 relative to the disk 10 (hereinafter sometimes referred to as back-EMF velocity information) generated by the reverse voltage generated by the VCM 14, the servo pattern control unit 620 controls the head 15 at a constant velocity to write the CGS servo pattern CGSS from the innermost radial direction, for example, the innermost circumference IMC, toward the outermost radial direction, for example, the outermost circumference OMC. Alternatively, the servo pattern control unit 620 may use the clock reference position of the blank disk 10 as the starting point and control the head 15 at a constant velocity based on the back-EMF velocity information to write the CGS servo pattern CGSS from the outermost radial direction, for example, the outermost circumference OMC, toward the innermost radial direction, for example, the innermost circumference IMC.

[0071] The CGS servo pattern control unit 620 writes a plurality of CGS servo patterns CGSS to a plurality of surfaces of the disk 10 by dividing them. For example, the CGS servo pattern control unit 620 writes a plurality of CGS servo patterns CGSS that should originally be written to one surface 10S of the disk 10 by dividing them to a plurality of surfaces of the disk 10. "Writing a plurality of CGS servo patterns to a plurality of surfaces by dividing them" means "writing a plurality of CGS servo patterns that are originally written to a single surface and written from the inner periphery to the outer periphery or from the outer periphery to the inner periphery of the disk 10 in a single stroke or continuously at intervals along the circumferential direction on one of the plurality of surfaces, and writing the other CGS servo patterns to the other surfaces of the plurality of surfaces at intervals along the circumferential direction on the other surfaces that are different from the aforementioned one surface." For example, “writing four CGS servo patterns to two surfaces by dividing them” means “writing at least one CGS servo pattern of the four CGS servo patterns that should have been written to one surface to one of the two surfaces, and writing the remaining CGS servo patterns of the four CGS servo patterns to the other of the two surfaces”. For example, the CGS servo pattern control unit 620 divides and writes a plurality of CGS servo patterns CGSS arranged in a circumferential direction on a virtual surface of the disk 10 to a plurality of surfaces of the disk 10 so that two CGS servo patterns CGSS that are adjacent in the circumferential direction among these CGS servo patterns CGSS are not arranged on the same surface. Here, “adjacent” means, not to mention that data, objects, areas, and spaces are arranged side by side, but also includes arranging predetermined objects separated by predetermined intervals, predetermined spaces, etc. In addition, “the situation of being adjacent on a virtual surface” is sometimes referred to as “virtual adjacent”. When writing a predetermined CGS servo pattern CGSS from among a plurality of CGS servo patterns CGSS onto a predetermined surface of the disk 10, the CGS servo pattern control unit 620 writes a CGS servo pattern CGSS written next to the predetermined CGS servo pattern CGSS (hereinafter sometimes referred to as the next CGS servo pattern) CGSS onto a surface different from the predetermined surface of the disk 10 on which the predetermined CGS servo pattern CGSS is written. In other words, the CGS servo pattern control unit 620 writes the CGS servo pattern CGSS into an area on the surface different from the predetermined surface, corresponding to an area corresponding to a region between two circumferentially adjacent CGS servo patterns CGSS on the predetermined surface.

[0072] The CGS servo pattern control unit 620 performs calibration for writing multiple CGS servo patterns CGSS, switches the multiple heads 15 corresponding to the multiple surfaces, and writes the multiple CGS servo patterns CGSS to the multiple surfaces 10S of the disk 10. In other words, the CGS servo pattern control unit 620 performs calibration for writing the multiple CGS servo patterns CGSS, switches between enabling (activating, valid, or ON) and disabling (deactivating, invalid, or OFF) write gates in the multiple heads 15 corresponding to the multiple surfaces 10S of the disk 10, and writes the multiple CGS servo patterns CGSS to the multiple surfaces 10S in a divided manner. The multiple CGS servo patterns CGSS written to the multiple surfaces 10S of the disk 10 have the same data structure and frequency. Terms such as "same," "identical," "identical," and "equivalent" not only mean completely identical, but also include differences to the extent that they can be considered substantially identical.

[0073] For example, the CGS servo pattern control unit 620 alternately writes odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 among the plurality of CGS servo patterns CGSS and even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 among the plurality of CGS servo patterns CGSS onto the front surface 10S0 of the disk 10-0 and onto the back surface 10S1 of the disk 10-0 while switching between the head 15-0 and the head 15-1. The CGS servo pattern control unit 620 writes the odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 among the plurality of CGS servo patterns CGSS onto the front surface 10S0 of the disk 10-0, and writes the even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 among the plurality of CGS servo patterns CGSS onto the back surface 10S1 of the disk 10-0 using the head 15-0. The CGS servo pattern control unit 620 enables the write strobe in the head 15-0 and disables the write strobe in the head 15-1, and uses the head 15-0 to write the odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 among the multiple CGS servo patterns CGSS to the surface 10S0 of the disk 10-0. The head 15-0 disables the write strobe and enables (asserts) the write strobe in the head 15-1, and uses the head 15-1 to write the even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 among the multiple CGS servo patterns CGSS to the surface 10S1 of the disk 10-0.

[0074] In addition, the CGS servo pattern control unit 620 can also write the odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 among the multiple CGS servo patterns CGSS to the back side 10S1 of the disk 10-0, the surface 10S2 of the disk 10-1, or the back side 10S3 of the disk 10-1, and write the even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 among the multiple CGS servo patterns CGSS to the back side 10S0 of the disk 10-0, the surface 10S2 of the disk 10-1, or the back side 10S3 of the disk 10-1 where the odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 are not written. In addition, the CGS servo pattern control unit 620 can also write the odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 among the multiple CGS servo patterns CGSS to the surface 10S0 of the disk 10-0 and the surface 10S2 of the disk 10-1, respectively, and write the even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 among the multiple CGS servo patterns CGSS to the back side 10S1 of the disk 10-0 and the back side 10S3 of the disk 10-1, respectively.

[0075] The CGS servo pattern control unit 620 performs calibration for writing a plurality of CGS servo patterns CGSS, switches the plurality of heads 15 corresponding to the plurality of surfaces 10S, and writes the plurality of CGS servo patterns CGSS onto the plurality of surfaces 10S. In other words, the CGS servo pattern control unit 620 performs calibration for writing a plurality of CGS servo patterns CGSS, switches between enabling (activating, valid, or ON) and disabling (deactivating, invalid, or OFF) write strobes in the plurality of heads 15 corresponding to the plurality of surfaces 10S, and writes the plurality of CGS servo patterns CGSS onto the plurality of surfaces in a divided manner.

[0076] For example, when odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 among a plurality of CGS servo patterns CGSS are written on the surface 10S0 and even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 are written on the back surface 10S1, the CGS servo pattern control unit 620 alternately reads the odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 and the even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 from the surface 10S0 of the disk 10-0 and the back surface 10S1 of the disk 10-0 while switching between the head 15-0 and the head 15-1. The CGS servo pattern control unit 620 uses the head 15-0 to read the odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 from the surface 10S0 of the disk 10-0 and uses the head 15-1 to read the even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 from the back surface 10S1. The CGS servo pattern control unit 620 enables the read strobe in the head 15-0 and disables the read strobe in the head 15-1, and uses the head 15-0 to read the odd CGS servo patterns CGSS2n+1 to CGSS2n+9 from the surface 10S0. The CGS servo pattern control unit 620 disables the read strobe in the head 15-1 and enables the read strobe in the head 15-1 to read the even CGS servo patterns CGSS2n+2 to CGSS2n+10 from the surface 10S1.

[0077] Figure 9 Schematic diagram showing an example of the arrangement of the CGS servo pattern CGSS of this embodiment. Figure 9 In FIG. 1 , the vertical axis represents the spiral direction from the inner circumference to the outer circumference, and the horizontal axis represents the interval (hereinafter sometimes simply referred to as interval) when one inner circumference of a plurality of CGS servo patterns is used as a reference. Figure 9 1 shows the direction of travel of the head 15. The direction in which the head 15 sequentially writes and reads data relative to the disk 10, that is, the direction in which the head 15 travels relative to the disk 10, is sometimes referred to as the travel direction. Figure 9 and Figure 4 correspond. Figure 9 The CGS servo patterns CGSS2n+1 to CGSS2n+10 are shown to be continuously arranged along the traveling direction on the imaginary surfaces of the front surface 10S0 and the back surface 10S1.

[0078] exist Figure 9In the illustrated example, the CGS servo pattern control unit 620 alternately writes odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 and even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 onto the front surface 10S0 and back surface 10S1 of the disk 10-0 while switching between heads 15-0 and 15-1. The CGS servo pattern control unit 620 uses head 15-0 as the starting point to write the odd-numbered CGS servo pattern CGSS2n+1 onto the front surface 10S0 from the inner side to the outer side based on back-EMF velocity information. Then, it switches from head 15-0 to head 15-1 and uses head 15-1 to write the even-numbered CGS servo pattern CGSS2n+2 onto the back surface 10S1 from the inner side to the outer side based on back-EMF velocity information. Based on the back EMF velocity information, the CGS servo pattern control unit 620 uses head 15-0 to write the odd CGS servo pattern CGSS2n+3 on the front surface 10S0 from the inner direction to the outer direction. Then, the head 15-0 is switched to head 15-1, and based on the back EMF velocity information, the head 15-1 is used to write the even CGS servo pattern CGSS2n+4 on the back surface 10S1 from the inner direction to the outer direction. Based on the back EMF velocity information, the CGS servo pattern control unit 620 uses head 15-0 to write the odd CGS servo pattern CGSS2n+5 on the front surface 10S0 from the inner direction to the outer direction. Then, the head 15-1 is switched from head 15-0 to head 15-1, and based on the back EMF velocity information, the head 15-1 is used to write the even CGS servo pattern CGSS2n+6 on the back surface 10S1 from the inner direction to the outer direction. The CGS servo pattern control unit 620 writes the odd CGS servo pattern CGSS2n+7 on the surface 10S0 from the inner direction to the outer direction by the head 15-0 based on the back electromotive force speed information, switches from the head 15-0 to the head 15-1, and writes the even CGS servo pattern CGSS2n+8 on the back side 10S1 from the inner direction to the outer direction by the head 15-1 based on the back electromotive force speed information. The CGS servo pattern control unit 620 writes the odd CGS servo pattern CGSS2n+9 on the surface 10S0 from the inner direction to the outer direction by the head 15-0 based on the back electromotive force speed information, switches from the head 15-0 to the head 15-1, and writes the even CGS servo pattern CGSS2n+10 on the back side 10S1 from the inner direction to the outer direction by the head 15-1 based on the back electromotive force speed information. Figure 9 In the example shown, CGP servo pattern CGSS2n+5 and CGP servo pattern CGSS2n+3 are adjacent to each other in region RG1 of the imaginary surfaces of the front surface 10S0 and the back surface 10S1 of the disk 10-0. That is, in region RG1, when the heads 15-0 and 15-1 are switched to read CGP servo pattern CGSS2n+5 and CGP servo pattern CGSS2n+3, the time intervals until the reading can be close.

[0079] Figure 10 Schematic diagram showing an example of the arrangement of the CGS servo pattern CGSS of this embodiment. Figure 10 In FIG. 1 , the vertical axis represents the spiral direction from the inner circumference toward the outer circumference, and the horizontal axis represents the interval when the inner circumference of one of the plurality of CGS servo patterns is used as a reference. Figure 10 Corresponding to Figure 5 . Figure 10 The CGS servo patterns CGSS2n+1 to CGSS2n+10 arranged in the traveling direction in the surface 10S0 in a top view are shown.

[0080] exist Figure 10 In the illustrated example, the CGS servo pattern control unit 620 writes odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+9 onto surface 10S0 of disk 10-0 from the inner circumference to the outer circumference by head 15-0 while switching between head 15-0 and head 15-1. The CGS servo pattern control unit 620 uses the clock reference position as a starting point and, based on back-EMF velocity information, writes odd-numbered CGS servo pattern CGSS2n+1 onto surface 10S0 from the inner circumference to the outer circumference by head 15-0. The CGS servo pattern control unit 620 writes odd-numbered CGS servo pattern CGSS2n+3 onto surface 10S0 from the inner circumference to the outer circumference by head 15-0 based on back-EMF velocity information. The CGS servo pattern control unit 620 writes odd-numbered CGS servo pattern CGSS2n+5 onto surface 10S0 from the inner circumference to the outer circumference by head 15-0 based on back-EMF velocity information. The CGS servo pattern control unit 620 writes the odd-numbered CGS servo pattern CGSS2n+7 on the surface 10S0 from the inner direction to the outer direction using the head 15-0 based on the back EMF velocity information. The CGS servo pattern control unit 620 writes the odd-numbered CGS servo pattern CGSS2n+9 on the surface 10S0 from the inner direction to the outer direction using the head 15-0 based on the back EMF velocity information.

[0081] Figure 11 Schematic diagram showing an example of the arrangement of the CGS servo pattern CGSS of this embodiment. Figure 11 In FIG. 1 , the vertical axis represents the spiral direction from the inner circumference toward the outer circumference, and the horizontal axis represents the interval when the inner circumference of one of the plurality of CGS servo patterns is used as a reference. Figure 11 Corresponding to Figure 6 . Figure 11 The CGS servo patterns CGSS2n+1 to CGSS2n+10 are shown arranged in the traveling direction on the surface 10S1 in a through-plan view.

[0082] exist Figure 11In the illustrated example, the CGS servo pattern control unit 620 writes even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 onto the surface 10S1 of the disk 10-0 from the inner circumference to the outer circumference, while switching between the head 15-0 and the head 15-1. The CGS servo pattern control unit 620 uses the clock reference position as the starting point and, based on back-EMF velocity information, writes the even-numbered CGS servo pattern CGSS2n+2 onto the surface 10S1 from the inner circumference to the outer circumference, using the head 15-1. Based on the back-EMF velocity information, the CGS servo pattern control unit 620 writes the even-numbered CGS servo pattern CGSS2n+4 onto the surface 10S1 from the inner circumference to the outer circumference, using the head 15-1. Based on the back-EMF velocity information, the CGS servo pattern control unit 620 writes the even-numbered CGS servo pattern CGSS2n+6 onto the surface 10S1 from the inner circumference to the outer circumference, using the head 15-1. The CGS servo pattern control unit 620 writes the even-numbered CGS servo pattern CGSS2n+8 on the surface 10S1 from the inner direction to the outer direction using the head 15-1 based on the back electromotive force velocity information. The CGS servo pattern control unit 620 writes the even-numbered CGS servo pattern CGSS2n+10 on the surface 10S1 from the inner direction to the outer direction using the head 15-1 based on the back electromotive force velocity information.

[0083] Figure 12 Schematic diagram showing an example of a method for writing and reading a CGS servo pattern according to this embodiment. Figure 10 In FIG. 1 , the vertical axis represents the spiral direction from the inner circumference toward the outer circumference, and the horizontal axis represents the interval when the inner circumference of one of the plurality of CGS servo patterns is used as a reference. Figure 12 Corresponding to Figure 9 . Figure 12 The read gates RG120 and RG121 are shown at predetermined radial positions of the imaginary surfaces of the front surface 10S0 and the back surface 10S1. Figure 12 In the read strobe RG120, if it is 0, the header 15-0 will be valid, and if it is 1, the header 15-1 will be valid. Figure 12 In the example, read strobe RG121 is set to 0 to enable header 15-0, and is set to 1 to enable header 15-1.

[0084] exist Figure 12 In the example shown, the CGS servo pattern control unit 620 switches the head 15-0 and the head 15-1 according to the read strobe RG120, and alternately reads the odd CGS servo patterns CGSS2n+1 to CGSS2n+9 and the even CGS servo patterns CGSS2n+2 to CGSS2n+10 from the surface 10S0 of the disk 10-0 and the back surface 10S1 of the disk 10-0.

[0085] exist Figure 12In the example shown, the CGS servo pattern control unit 620 switches the head 15-0 and the head 15-1 according to the read strobe RG121, and alternately reads the odd CGS servo patterns CGSS2n+1 to CGSS2n+9 and the even CGS servo patterns CGSS2n+2 to CGSS2n+10 from the surface 10S0 of the disk 10-0 and the back surface 10S1 of the disk 10-0.

[0086] The measurement unit 630 measures the plurality of CGS servo patterns. The measurement unit 630 reads and measures the plurality of CGS servo patterns written to the plurality of surfaces of the disk 10 by dividing the plurality of CGS servo patterns, while switching the plurality of heads 15 corresponding to the plurality of surfaces.

[0087] The measuring unit 630 changes (or adjusts) the measuring method or reading method of these CGS servo patterns CGSS based on the circumferential interval between two imaginary adjacent CGS servo patterns CGSS within a plurality of CGS servo patterns CGSS arranged in the circumferential direction at a predetermined radial position on the imaginary surface of the disk 10 (hereinafter sometimes referred to as the imaginary CGS interval).

[0088] If the measurement unit 630 determines that the virtual CGS interval between two virtual adjacent CGS servo patterns CGSS within a plurality of CGS servo patterns CGSS circumferentially arranged at predetermined radial positions on the virtual surface of the disk 10 is greater than a sufficient distance (hereinafter, the "switchable interval") for switching and reading the plurality of heads 15 corresponding to different surfaces of the disk 10, it measures the circumferential positions (hereinafter, sometimes referred to as actual CGS positions) of the plurality of CGS servo patterns CGSS written to the plurality of surfaces 10S of the disk 10 and the virtual CGS intervals corresponding to the respective CGS actual positions while switching the plurality of heads 15. The measurement unit 630 then measures or calculates, for example, the RRO correction data corresponding to each actual CGS position based on the measured actual CGS positions. Hereinafter, "measuring or calculating RRO correction data based on the RRO correction amount" may also be referred to as "RRO learning." Furthermore, measuring the actual CGS positions of the CGS servo patterns CGSS may also be referred to as CGS search. The measurement unit 630 may also record the measured actual CGS position, virtual CGS interval, and RRO correction data as a table in a predetermined recording area, such as the system area 10b of the disk 10, the volatile memory 70, or the nonvolatile memory 80.

[0089] When the measuring unit 630 determines that the imaginary CGS interval between two imaginary adjacent CGS servo patterns CGSS within a plurality of CGS servo patterns CGSS arranged in the circumferential direction at a predetermined radial position on the imaginary surface of the disk 10 is greater than the switchable interval, the measuring unit 630 reads the plurality of CGS servo patterns CGSS arranged in the circumferential direction while switching the plurality of heads 15, and measures the actual CGS positions corresponding to each of the plurality of CGS servo patterns CGSS.

[0090] For example, when the measuring unit 630 determines that the imaginary CGS interval between two imaginary adjacent CGS servo patterns CGSS that are adjacent in the circumferential direction and written on different surfaces at a radial position of the imaginary surface of the disk 10, for example, on a predetermined track, is greater than the switchable interval, the measuring unit 630 alternately reads these CGS servo patterns CGSS while switching the multiple heads 15, and measures the two actual CGS positions corresponding to each of these CGS servo patterns CGSS.

[0091] When the measurement unit 630 determines that the virtual CGS interval between two virtual adjacent CGS servo patterns CGSS within a plurality of CGS servo patterns CGSS circumferentially arranged at a predetermined radial position on the virtual surface of the disk 10 is smaller than the switchable interval, the measurement unit 630 repeatedly measures, at the same radial position, each actual position and each circumferential interval (hereinafter sometimes referred to as the actual CGS interval) between two circumferentially adjacent CGS servo patterns CGSS within the plurality of CGS servo patterns CGSS corresponding to each actual position, written on the plurality of surfaces 10S of the disk 10. The measurement unit 630 combines the plurality of actual CGS intervals corresponding to each actual position on the plurality of surfaces 10S of the disk 10 to calculate the virtual CGS interval corresponding to each actual position.

[0092] When the measuring unit 630 determines that the imaginary CGS interval between two imaginary adjacent CGS servo patterns CGSS within a plurality of CGS servo patterns CGSS arranged in the circumferential direction at a predetermined radial position on the imaginary surface of the disk 10 is smaller than the switchable interval, the measuring unit 630 reads the plurality of CGS servo patterns CGSS arranged in the circumferential direction multiple times at the same radial position while switching the plurality of heads 15, and measures the actual CGS positions corresponding to each of the plurality of CGS servo patterns CGSS.

[0093] For example, when the measuring unit 630 determines that the imaginary CGS interval between two CGS servo patterns CGSS that are adjacent in the circumferential direction and written on different surfaces at a radial position on the imaginary surface of the disk 10, for example, on a predetermined track, is smaller than the switchable interval, one of these CGS servo patterns CGSS is read in the first cycle using a predetermined head 15, and the other CGS servo pattern CGSS that has not been read yet is read using another head 15 different from the predetermined head 15, and the two actual CGS positions corresponding to these CGS servo patterns CGSS are measured.

[0094] The measurement unit 630 changes the switchable interval based on the virtual CGS interval that changes with the seek direction and speed of the head 15. Based on the actual positions of each CGS data pattern at each radial position on the virtual surface of the disk 10 and the switchable interval, the measurement unit 630 sets an area that can be read by switching multiple heads 15 (hereinafter sometimes referred to as a switchable area) and an area that cannot be read by switching multiple heads 15 (hereinafter sometimes referred to as a non-switchable area). The measurement unit 630 may also record the switchable and non-switchable areas as a table in a predetermined recording area, such as the system area 10b of the disk 10, the volatile memory 70, or the non-volatile memory 80.

[0095] When reading the CGS servo pattern CGSS of the non-switchable area of the imaginary surface of the disk 10, the measuring unit 630 calculates (or estimates) the actual CGS position (hereinafter sometimes referred to as the estimated CGS position) corresponding to the predetermined CGS servo pattern CGSS corresponding to the next radial position (hereinafter sometimes referred to as the next radial position) adjacent in the radial direction to the current radial position based on the imaginary CGS interval (hereinafter sometimes referred to as the current imaginary CGS interval) corresponding to the predetermined CGS servo pattern CGSS at the current radial position and the imaginary CGS (hereinafter sometimes referred to as the previous imaginary CGS interval) corresponding to the predetermined CGS servo pattern CGSS at the previous radial position adjacent in the radial direction to the current radial position.

[0096] For example, when reading the CGS servo pattern CGSS of the non-switchable area of the imaginary surface of the disk 10, the measuring unit 630 calculates (or estimates) the estimated CGS position corresponding to the predetermined CGS servo pattern CGSS corresponding to the next track (hereinafter sometimes referred to as the next track) adjacent in the radial direction to the current track based on the current imaginary CGS interval corresponding to the predetermined CGS servo pattern CGSS of the current track and the previous imaginary CGS interval corresponding to the predetermined CGS servo pattern CGSS of the previous track adjacent in the radial direction to the current track (hereinafter sometimes referred to as the previous track).

[0097] When reading the CGS servo pattern CGSS located in the non-switchable area, the measurement unit 630 calculates a virtual CGS interval corresponding to the estimated CGS position (hereinafter sometimes referred to as the estimated virtual CGS interval) based on the estimated CGS position. Based on the estimated virtual CGS interval, the measurement unit 630 seeks the head 15 in the non-switchable area, reads the predetermined CGS servo pattern CGSS, and measures the actual CGS position corresponding to the CGS servo pattern CGSS. The measurement unit 630 updates the estimated CGS position corresponding to the CGS servo pattern CGSS in the non-switchable area with the measured actual CGS position, minimizing the estimation error.

[0098] Figure 13 1 is a schematic diagram showing an example of a method for reading a plurality of CGS servo patterns CGSS written on different surfaces 10S when the virtual CGS interval is smaller than the switchable interval in this embodiment. Figure 13 In the upper figure, the vertical axis represents the spiral direction from the inner circumference to the outer circumference, and the horizontal axis represents the interval when the inner circumference of one of the multiple CGS servo patterns is used as a reference. Figure 13 The vertical axis of the upper graph represents the radial position RP13. Figure 13The upper figure shows CGS servo patterns CGSS2m+1, CGSS2m+2, CGSS2m+3, CGSS2m+4, CGSS2m+5, CGSS2m+6, CGSS2m+7, CGSS2m+8, CGSS2m+9, and CGSS2m+10, which are arranged continuously along the traveling direction on the imaginary surface 10S of the disk 10. M is an integer greater than or equal to 0. The CGS servo patterns CGSS2m+1, CGSS2m+3, CGSS2m+5, CGSS2m+7, and CGSS2m+9 are odd-numbered CGS servo patterns. The CGS servo patterns CGSS2m+2, CGSS2m+4, CGSS2m+6, CGSS2m+8, and CGSS2m+10 are even-numbered CGS servo patterns. The odd-numbered CGS servo patterns CGSS2m+1, CGSS2m+3, CGSS2m+5, CGSS2m+7, and CGSS2m+9, and the even-numbered CGS servo patterns CGSS2m+2, CGSS2m+4, CGSS2m+6, CGSS2m+8, and CGSS2m+10 are written to different sides 10S of the disk 10, respectively. Figure 13 At the radial position RP13 of the imaginary surface of the disk 10 in the upper figure, the odd-numbered CGS servo pattern CGSS2m+7 and the even-numbered CGS servo pattern CGSS2m+6 are crossed and their order is reversed. Figure 13 The figure below shows the read gates RG130 and RG131 at predetermined radial positions of the imaginary surface 10S of the disk 10. Figure 13 The figure below shows the actual CGS positions of the odd-numbered CGS servo patterns CGSS2m+1 to CGSS2m+9 at predetermined radial positions on the imaginary surface 10S of the disk 10 (hereinafter sometimes referred to as odd actual CGS positions), and the actual CGS positions of the even-numbered CGS servo patterns CGSS2m+2 to CGSS2m+10 at predetermined radial positions on the imaginary surface 10S of the disk 10 (hereinafter sometimes referred to as even actual CGS positions). Figure 13 In FIG. 1 , the odd-numbered actual CGS positions at predetermined radial positions of the imaginary surface 10S of the disk 10 are indicated by hollow diamonds. Figure 13 In FIG. 1 , even-numbered actual CGS positions at predetermined radial positions on the imaginary surface 10S of the disk 10 are indicated by diagonally shaded diamonds. Figure 13 It shows a plurality of actual CGS positions CP13 corresponding to a plurality of CGS servo patterns CGSS of a radial position RP of an imaginary surface 10S of a disk 10, which are synthesized by combining a plurality of actual CGS positions corresponding to a plurality of CGS servo patterns CGSS read out according to a read strobe RG130 and a plurality of actual CGS positions corresponding to a plurality of CGS servo patterns CGSS read out according to a read strobe RG131.

[0099] exist Figure 13 In the example shown, when the measuring unit 630 determines that the virtual CGS interval between the odd-numbered CGS servo pattern CGSS2m+7 and the even-numbered CGS servo pattern CGSS2m+6 is smaller than the switchable interval at the radial position RP13 of the virtual surface 10S of the disk 10, the measuring unit 630 reads the CGS servo patterns CGSS2m+1, CGSS2m+2, CGSS2m+3, CGSS2m+4, CGSS2m+5, CGSS2m+6, CGSS2m+8, CGSS2m+9, and CGSS2m+10 in the order listed for the first cycle while alternately switching the multiple heads 15, and measures the multiple actual CGSs corresponding to the CGS servo patterns CGSS2m+1, CGSS2m+2, CGSS2m+3, CGSS2m+4, CGSS2m+5, CGSS2m+6, CGSS2m+8, CGSS2m+9, and CGSS2m+10, respectively. In the first round, the measuring unit 630 does not read the odd-numbered CGS servo pattern CGSS2m+7 but reads the even-numbered CGS servo pattern CGSS2m+6.

[0100] exist Figure 13 In the example shown, when the measuring unit 630 determines that the imaginary CGS interval between the odd-numbered CGS servo pattern CGSS2m+7 and the even-numbered CGS servo pattern CGSS2m+6 is smaller than the switchable interval at the radial position RP13 of the imaginary surface 10S of the disk 10, the measuring unit 630 reads the CGS servo patterns CGSS2m+1, CGSS2m+2, CGSS2m+3, CGSS2m+4, CGSS2m+5, CGSS2m+7, CGSS2m+8, CGSS2m+9, and CGSS2m+10 in the order listed for the second round while alternately switching the multiple heads 15, and measures the multiple actual CGSs corresponding to the CGS servo patterns CGSS2m+1, CGSS2m+2, CGSS2m+3, CGSS2m+4, CGSS2m+5, CGSS2m+7, CGSS2m+8, CGSS2m+9, and CGSS2m+10, respectively. In the second round, the measuring unit 630 does not read the odd-numbered CGS servo pattern CGSS2m+6 but reads the even-numbered CGS servo pattern CGSS2m+7.

[0101] The measurement unit 630 synthesizes the multiple actual CGSs corresponding to the CGS servo patterns CGSS2m+1, CGSS2m+2, CGSS2m+3, CGSS2m+4, CGSS2m+5, CGSS2m+6, CGSS2m+8, CGSS2m+9, and CGSS2m+10, respectively, and the multiple actual CGSs corresponding to the CGS servo patterns CGSS2m+1, CGSS2m+2, CGSS2m+3, CGSS2m+4, CGSS2m+5, CGSS2m+7, CGSS2m+8, CGSS2m+9, and CGSS2m+10, respectively, to obtain multiple actual CGS positions CP13.

[0102] Figure 14 This is a schematic diagram showing an example of a method for setting a non-switchable area according to the present embodiment. Figure 14 The diagram shows CGS servo patterns CGSS2k-2, CGSS2k-1, and CGSS2k arranged consecutively in the traveling direction on the imaginary surface of the disk 10. k is an integer greater than or equal to 0. The CGS servo pattern CGSS2k-1 is an odd-numbered CGS servo pattern. The CGS servo patterns CGSS2k-2 and CGSS2k are even-numbered CGS servo patterns. The odd-numbered CGS servo pattern CGSS2k-1 and the even-numbered CGS servo patterns CGSS2k-2 and CGSS2k are written to different surfaces 10S of the disk 10. Figure 14 A switchable interval T1 is shown. Figure 14 Shown are the change in the seek direction of the position of the switchable interval T1 corresponding to the CGS servo pattern CGSS2k-2 (hereinafter sometimes referred to as the change in the switchable interval corresponding to the CGS servo pattern CGSS2k-2) APL2k-2, and the change in the seek direction of the position of the switchable interval T1 corresponding to the CGS servo pattern CGSS2k-1 (hereinafter sometimes referred to as the change in the switchable interval corresponding to the CGS servo pattern CGSS2k-1) APL2k-1. Figure 14 The non-switchable region NSR14 and the switchable region SR14 are shown. Figure 14 In the plan view, in the non-switchable region NSR14, the CGS servo pattern CGSS2k-1 and the CGS servo pattern CGSS2k are adjacent to each other.

[0103] like Figure 14 As shown, the measuring unit 630 sets a region where the virtual CGS interval between the odd CGS servo pattern CGSS2k-1 and the even CGS servo pattern CGSS2k is greater than the switchable interval T1 as a switchable region SR14 based on the change APL2k-1 of the switchable interval corresponding to the CGS servo pattern CGSS2k-1.

[0104] like Figure 14 As shown, the measuring unit 630 sets the area where the virtual CGS interval between the odd CGS servo pattern CGSS2k-1 and the even CGS servo pattern CGSS2k is smaller than the switchable interval T1 as the non-switchable area NSR14 based on the change APL2k-1 of the switchable interval corresponding to the CGS servo pattern CGSS2k-1.

[0105] Figure 15 This is a schematic diagram showing an example of a method for setting a non-switchable area according to the present embodiment. Figure 15 The non-switchable region NSR15 and the switchable region SR15 are shown. Figure 15 In the plan view, in the non-switchable region NSR15 , the CGS servo pattern CGSS2 k- 1 intersects the CGS servo pattern CGSS2 k.

[0106] like Figure 15 As shown, the measuring unit 630 sets a region where the virtual CGS interval between the odd CGS servo pattern CGSS2k-1 and the even CGS servo pattern CGSS2k is greater than the switchable interval T1 as a switchable region SR15 based on the change APL2k-1 of the switchable interval corresponding to the CGS servo pattern CGSS2k-1.

[0107] like Figure 15 As shown, the measuring unit 630 sets the area where the virtual CGS interval between the odd CGS servo pattern CGSS2k-1 and the even CGS servo pattern CGSS2k is smaller than the switchable interval T1 as the non-switchable area NSR15 based on the change APL2k-1 of the switchable interval corresponding to the CGS servo pattern CGSS2k-1.

[0108] Figure 16 Schematic diagram showing an example of a change in the switchable interval in this embodiment. Figure 16 In the figure, the vertical axis represents the radial direction and the horizontal axis represents the circumferential direction. Figure 161. The CGS servo patterns CGSS21+1, CGSS21+2, CGSS21+3, CGSS21+4, CGSS21+5, CGSS21+6, CGSS21+7, CGSS21+8, CGSS21+9, and CGSS21+10 are shown as being arranged continuously along the circumferential direction of travel on the imaginary surface 10S of the disk 10. L is an integer greater than or equal to 0. The CGS servo patterns CGSS21+1, CGSS21+3, CGSS21+5, CGSS21+7, and CGSS21+9 are odd-numbered CGS servo patterns. The CGS servo patterns CGSS21+2, CGSS21+4, CGSS21+6, CGSS21+8, and CGSS21+10 are even-numbered CGS servo patterns. The odd-numbered CGS servo patterns CGSS21+1, CGSS21+3, CGSS21+5, CGSS21+7, and CGSS21+9, and the even-numbered CGS servo patterns CGSS21+2, CGSS21+4, CGSS21+6, CGSS21+8, and CGSS21+10 are written to different sides 10S of the disk 10, respectively. Figure 16 2 shows a seek direction from the inner periphery to the outer periphery (hereinafter, sometimes referred to as a seek direction) SKD1 and a seek direction SKD2 from the outer periphery to the inner periphery. Figure 16 The lower side of FIG shows the odd actual CGS positions of the odd CGS servo patterns CGSS21+1 to CGSS21+9 read along the seek direction SKD1 on the imaginary surface 10S of the disk 10, and the even actual CGS positions of the even CGS servo patterns CGSS21+2 to CGSS21+10 read along the seek direction SKD1. Figure 16 The upper side of FIG. 1 shows the odd actual CGS positions of the odd CGS servo patterns CGSS21+1 to CGSS21+9 read along the seek direction SKD2 on the imaginary surface 10S of the disk 10, and the even actual CGS positions of the even CGS servo patterns CGSS21+2 to CGSS21+10 read along the seek direction SKD2. Figure 16 In FIG. 1 , the odd-numbered actual CGS positions at predetermined radial positions of the imaginary surface 10S of the disk 10 are indicated by hollow diamonds. Figure 16 In FIG. 1 , even-numbered actual CGS positions at predetermined radial positions on the imaginary surface 10S of the disk 10 are indicated by diagonally shaded diamonds. Figure 16 An imaginary CGS interval IT1 between the CGS servo pattern CGSS21+1 and the CGS servo pattern CGSS21+2 along the tracking direction SKD1 and an imaginary CGS interval IT2 between the CGS servo pattern CGSS21+1 and the CGS servo pattern CGSS21+2 along the tracking direction SKD2 are shown.

[0109] exist Figure 16 In the example shown, the virtual CGS interval IT1 along the seek direction SKD1 is different from the virtual CGS interval IT2 along the seek direction SKD2. Therefore, the measuring unit 630 changes the switchable intervals in the seek direction SKD1 and the seek direction SKD2.

[0110] Figure 17 10 is a schematic diagram showing an example of measurement of an actual CGS interval corresponding to the odd-numbered CGS servo pattern CGSS written on the surface 10S0 according to the present embodiment. Figure 17 Corresponding to Figure 10 . Figure 17 Shown are a clock reference position CBP and an odd-numbered CGS servo pattern CGSS2n+11 adjacent to the odd-numbered CGS servo pattern CGSS2n+9 in the traveling direction on the surface 10S0. Figure 17 A radial position RP17 on the surface 10S0 is shown. Figure 17 The actual CGS interval a1 between the clock reference position CBP at the radial position RP17 of the surface 10S0 and the odd CGS servo pattern CGSS2n+1, the actual CGS interval a2 between the odd CGS servo pattern CGSS2n+1 and the odd CGS servo pattern CGSS2n+3 at the radial position RP17 of the surface 10S0, the actual CGS interval a3 between the odd CGS servo pattern CGSS2n+3 and the odd CGS servo pattern CGSS2n+5 at the radial position RP17 of the surface 10S0, and the actual CGS interval a4 between the odd CGS servo pattern CGSS2n+1 and the odd CGS servo pattern CGSS2n+3 at the radial position RP17 of the surface 10S0 are shown. The actual CGS interval a4 between the odd CGS servo pattern CGSS2n+5 and the odd CGS servo pattern CGSS2n+7 at the radial position RP17 of 0S0, the actual CGS interval a5 between the odd CGS servo pattern CGSS2n+7 and the odd CGS servo pattern CGSS2n+9 at the radial position RP17 of the surface 10S0, and the actual CGS interval a6 between the odd CGS servo pattern CGSS2n+9 and the odd CGS servo pattern CGSS2n+11 at the radial position RP17 of the surface 10S0.

[0111] exist Figure 17 In the illustrated example, the measuring unit 630 measures a plurality of odd-numbered actual CGS positions corresponding to a plurality of odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+11 at the radial position RP17 of the surface 10S0 .

[0112] The measuring unit 630 calculates the actual CGS interval a1 between the clock reference position at the radial position RP17 and the odd CGS servo pattern CGSS2n+1 based on the clock reference position CBP at the radial position RP17 of the surface 10S0 and the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+1.

[0113] The measuring unit 630 calculates the actual CGS interval a2 between the odd CGS servo pattern CGSS2n+1 and the odd CGS servo pattern CGSS2n+3 at the radial position RP17 based on the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+1 and the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+3 at the radial position RP17 of the surface 10S0.

[0114] The measuring unit 630 calculates the actual CGS interval a3 between the odd CGS servo pattern CGSS2n+3 and the odd CGS servo pattern CGSS2n+5 at the radial position RP17 based on the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+3 and the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+5 at the radial position RP17 of the surface 10S0.

[0115] The measuring unit 630 calculates the actual CGS interval a4 between the odd CGS servo pattern CGSS2n+5 and the odd CGS servo pattern CGSS2n+7 at the radial position RP17 based on the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+5 and the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+7 at the radial position RP17 of the surface 10S0.

[0116] The measuring unit 630 calculates the actual CGS interval a5 between the odd CGS servo pattern CGSS2n+7 and the odd CGS servo pattern CGSS2n+9 at the radial position RP17 based on the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+7 and the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+9 at the radial position RP17 of the surface 10S0.

[0117] The measuring unit 630 calculates the actual CGS interval a6 between the odd CGS servo pattern CGSS2n+9 and the odd CGS servo pattern CGSS2n+11 at the radial position RP17 based on the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+9 and the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+11 at the radial position RP17 of the surface 10S0.

[0118] Figure 18 This is a schematic diagram showing an example of measurement of an even-numbered actual CGS interval corresponding to an even-numbered CGS servo pattern written on the back side 10S1 according to the present embodiment. Figure 18 Corresponding to Figure 11 .exist Figure 18 2 , a clock reference position CBP and an odd-numbered CGS servo pattern CGSS2n+11 are shown. Figure 18 A radial position RP17 on the back surface 10S1 is shown. Figure 18 The diagram shows the actual CGS interval b1 between the clock reference position CBP at the radial position RP17 of the back surface 10S1 and the even CGS servo pattern CGSS2n+2, the actual CGS interval b2 between the even CGS servo pattern CGSS2n+2 and the even CGS servo pattern CGSS2n+4 at the radial position RP17 of the back surface 10S1, the actual CGS interval b3 between the even CGS servo pattern CGSS2n+4 and the even CGS servo pattern CGSS2n+6 at the radial position RP17 of the back surface 10S1, and the actual CGS interval b4 between the even CGS servo pattern CGSS2n+6 and the even CGS servo pattern CGSS2n+6 at the radial position RP17 of the back surface 10S1. The actual CGS interval b4 between the even CGS servo pattern CGSS2n+6 and the even CGS servo pattern CGSS2n+8 at the radial position RP17 of S1, the actual CGS interval b5 between the even CGS servo pattern CGSS2n+8 and the even CGS servo pattern CGSS2n+10 at the radial position RP17 of the back side 10S1, and the actual CGS interval b6 between the even CGS servo pattern CGSS2n+10 and the odd CGS servo pattern CGSS2n+11 at the radial position RP17 of the back side 10S1.

[0119] exist Figure 18 In the illustrated example, the measuring unit 630 measures a plurality of actual CGS positions corresponding to a plurality of even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+11 at the radial position RP17 of the rear surface 10S1.

[0120] The measuring unit 630 calculates the actual CGS interval b1 between the clock reference position CBP and the even CGS servo pattern CGSS2n+2 based on the clock reference position CBP at the radial position RP17 of the rear surface 10S1 and the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+2.

[0121] The measuring unit 630 calculates the actual CGS interval b2 between the even CGS servo pattern CGSS2n+2 and the even CGS servo pattern CGSS2n+4 at the radial position RP17 based on the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+2 and the odd actual CGS position corresponding to the even CGS servo pattern CGSS2n+4 at the radial position RP17 of the back side 10S1.

[0122] The measuring unit 630 calculates the actual CGS interval b3 between the even CGS servo pattern CGSS2n+4 and the even CGS servo pattern CGSS2n+6 at the radial position RP17 based on the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+4 and the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+6 at the radial position RP17 of the back side 10S1.

[0123] The measuring unit 630 calculates the actual CGS interval b4 between the even CGS servo pattern CGSS2n+6 and the even CGS servo pattern CGSS2n+8 at the radial position RP17 based on the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+6 and the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+8 at the radial position RP17 of the back side 10S1.

[0124] The measuring unit 630 calculates the actual CGS interval b5 between the even CGS servo pattern CGSS2n+8 and the even CGS servo pattern CGSS2n+10 at the radial position RP17 based on the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+8 and the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+10 at the radial position RP17 of the back side 10S1.

[0125] The measuring unit 630 calculates the actual CGS interval b6 between the even CGS servo pattern CGSS2n+10 and the odd CGS servo pattern CGSS2n+11 at the radial position RP17 based on the even actual CGS position corresponding to the even CGS servo pattern CGSS2n+10 and the odd actual CGS position corresponding to the odd CGS servo pattern CGSS2n+11 at the radial position RP17 of the back side 10S1.

[0126] Figure 19 Yes Figure 17 The actual CGS interval is different from Figure 18 Schematic diagram of an example of the synthesis of the actual CGS interval. Figure 19 Corresponding to Figure 17 as well as Figure 18 . Figure 19 The imaginary surfaces of the front surface 10S0 and the back surface 10S1 are shown. Figure 19 The radial position RP17 on the imaginary plane of the front surface 10S0 and the back surface 10S1 is shown.

[0127] exist Figure 19In the example shown, the measuring unit 630 synthesizes the multiple actual CGS intervals corresponding to the multiple odd-numbered CGS servo patterns CGSS2n+1 to CGSS2n+11 on the radial position RP17 of the imaginary surface 10S of the surface 10S0 and the back surface 10S1, and the multiple actual CGS intervals corresponding to the multiple even-numbered CGS servo patterns CGSS2n+2 to CGSS2n+10 on the radial position RP17, and calculates the imaginary CGS intervals corresponding to the multiple CGS servo patterns CGSS2n+1, CGSS2n+2, CGSS2n+1CGSS2n+3, CGSS2n+4, CGSS2n+5, CGSS2n+6, CGSS2n+7, CGSS2n+8, CGSS2n+9, and CGSS2n+10 on the radial position RP17.

[0128] The measuring unit 630 calculates the imaginary CGS interval c2 = b1 - a1 between the odd CGS servo pattern CGSS2n+1 and the even CGS servo pattern CGSS2n+2 at the radial position RP17 based on the actual CGS interval a1 between the clock reference position CBP at the radial position RP17 and the odd CGS servo pattern CGSS2n+1, and the actual CGS interval b1 between the clock reference position CBP at the radial position RP17 and the even CGS servo pattern CGSS2n+2.

[0129] The measuring unit 630 calculates the imaginary CGS interval c3 = a2 - c2 between the even CGS servo pattern CGSS2n+2 and the odd CGS servo pattern CGSS2n+3 at the radial position RP17 based on the actual CGS interval a2 between the odd CGS servo pattern CGSS2n+1 and the odd CGS servo pattern CGSS2n+3 at the radial position RP17 and the imaginary CGS interval c2 between the odd CGS servo pattern CGSS2n+1 and the even CGS servo pattern CGSS2n+2 at the radial position RP17.

[0130] The measuring unit 630 calculates the imaginary CGS interval c4 = b2 - c3 between the odd CGS servo pattern CGSS2n+3 and the even CGS servo pattern CGSS2n+4 at the radial position RP17 based on the actual CGS interval b2 between the even CGS servo pattern CGSS2n+2 and the even CGS servo pattern CGSS2n+4 at the radial position RP17 and the imaginary CGS interval c3 between the even CGS servo pattern CGSS2n+2 and the odd CGS servo pattern CGSS2n+3 at the radial position RP17.

[0131] The measuring unit 630 calculates the imaginary CGS interval c5 = a3 - c4 between the even CGS servo pattern CGSS2n+4 and the odd CGS servo pattern CGSS2n+5 at the radial position RP17 based on the actual CGS interval a3 between the odd CGS servo pattern CGSS2n+3 and the odd CGS servo pattern CGSS2n+5 at the radial position RP17 and the imaginary CGS interval c4 between the odd CGS servo pattern CGSS2n+3 and the even CGS servo pattern CGSS2n+4 at the radial position RP17.

[0132] The measuring unit 630 calculates the imaginary CGS interval c6 = b3 - c5 between the odd CGS servo pattern CGSS2n+5 and the even CGS servo pattern CGSS2n+6 at the radial position RP17 based on the actual CGS interval b3 between the even CGS servo pattern CGSS2n+4 and the even CGS servo pattern CGSS2n+6 at the radial position RP17 and the imaginary CGS interval c5 between the odd CGS servo pattern CGSS2n+3 and the even CGS servo pattern CGSS2n+4 at the radial position RP17.

[0133] The measuring unit 630 calculates the imaginary CGS interval c7 = a4 - c6 between the even CGS servo pattern CGSS2n+6 and the odd CGS servo pattern CGSS2n+7 at the radial position RP17 based on the actual CGS interval a4 between the odd CGS servo pattern CGSS2n+5 and the odd CGS servo pattern CGSS2n+7 at the radial position RP17 and the imaginary CGS interval c6 between the odd CGS servo pattern CGSS2n+5 and the even CGS servo pattern CGSS2n+6 at the radial position RP17.

[0134] The measuring unit 630 calculates the imaginary CGS interval c8 = b4 - c7 between the odd CGS servo pattern CGSS2n+7 and the even CGS servo pattern CGSS2n+8 at the radial position RP17 based on the actual CGS interval b4 between the even CGS servo pattern CGSS2n+6 and the even CGS servo pattern CGSS2n+8 at the radial position RP17 and the imaginary CGS interval c7 between the even CGS servo pattern CGSS2n+6 and the odd CGS servo pattern CGSS2n+7 at the radial position RP17.

[0135] The measuring unit 630 calculates the imaginary CGS interval c9 = a5 - c8 between the even CGS servo pattern CGSS2n+8 and the odd CGS servo pattern CGSS2n+9 at the radial position RP17 based on the actual CGS interval a5 between the odd CGS servo pattern CGSS2n+7 and the odd CGS servo pattern CGSS2n+9 at the radial position RP17 and the imaginary CGS interval c8 between the odd CGS servo pattern CGSS2n+7 and the even CGS servo pattern CGSS2n+8 at the radial position RP17.

[0136] The measuring unit 630 calculates the imaginary CGS interval c10 = b5 - c9 between the odd CGS servo pattern CGSS2n+9 and the even CGS servo pattern CGSS2n+10 at the radial position RP17 based on the actual CGS interval b5 between the even CGS servo pattern CGSS2n+8 and the even CGS servo pattern CGSS2n+10 at the radial position RP17 and the imaginary CGS interval c9 between the even CGS servo pattern CGSS2n+8 and the odd CGS servo pattern CGSS2n+9 at the radial position RP17.

[0137] The measuring unit 630 calculates the imaginary CGS interval c11 = a6 - c10 between the even CGS servo pattern CGSS2n+10 and the odd CGS servo pattern CGSS2n+11 at the radial position RP17 based on the actual CGS interval a6 between the odd CGS servo pattern CGSS2n+9 and the odd CGS servo pattern CGSS2n+11 at the radial position RP17 and the imaginary CGS interval c10 between the odd CGS servo pattern CGSS2n+9 and the even CGS servo pattern CGSS2n+10 at the radial position RP17.

[0138] Figure 20 Schematic diagram showing an example of the measurement results of the change of RRO in this embodiment. Figure 20 In the left figure, the vertical axis represents the spiral direction from the inner circumference to the outer circumference, and the horizontal axis represents the circumferential direction. Figure 20The left figure shows CGS servo patterns CGSS2k+3, CGSS2k+4, CGSS2k+5, CGSS2k+6, CGSS2k+7, CGSS2k+8, CGSS2k+9, CGSS2k+10, CGSS2k+11, and CGSS2k+12, which are arranged continuously in the circumferential direction of travel on the imaginary surface 10S of the disk 10. K is an integer greater than or equal to 0. The CGS servo patterns CGSS2k+3, CGSS2k+5, CGSS2k+7, CGSS2k+9, and CGSS2k+11 are odd-numbered CGS servo patterns. The CGS servo patterns CGSS2k+4, CGSS2k+6, CGSS2k+8, CGSS2k+10, and CGSS2k+12 are even-numbered CGS servo patterns. The odd-numbered CGS servo patterns CGSS2k+3, CGSS2k+5, CGSS2k+7, CGSS2k+9, and CGSS2k+11, and the even-numbered CGS servo patterns CGSS2k+4, CGSS2k+6, CGSS2k+8, CGSS2k+10, and CGSS2k+12 are written to different surfaces 10S of the disk 10, respectively. Figure 20 At a predetermined radial position of the imaginary surface 10S of the disk 10 in the left figure, the odd-numbered CGS servo pattern CGSS2k+9 and the even-numbered CGS servo pattern CGSS2k+8 intersect and are reversed in order. Figure 20 In the right figure, the vertical axis represents Figure 20 The RRO corresponding to each radial position on the left side of the , the horizontal axis represents the circumferential direction. Figure 20 The right figure shows the intersection area CSC corresponding to each radial position of the odd CGS servo pattern CGSS2k+9 and the even CGS servo pattern CGSS2k+8. Figure 20 The intersection area CSC of the right figure shows the change in RRO at each radial position (hereinafter sometimes simply referred to as the change in RRO) CXL obtained by writing multiple CGS servo patterns CGSS2k+3 to CGSS2k+12 on the same surface, and the change in RRO EML at each radial position obtained by writing multiple odd-numbered CGS servo patterns CGSS2k+3 to CGSS2k+11 and multiple even-numbered CGS servo patterns CGSS2k+4 to CGSS2k+12 on different surfaces in this embodiment.

[0139] like Figure 20As shown in the RRO change CXL, since the multiple CGS servo patterns CGSS2k+3 to CGSS2k+12 have the same data structure and / or frequency, it is difficult to detect that the order of these CGS servo patterns CGSS2k+3 to CGSS2k12 is reversed when they are written to the same surface and a portion of the CGS servo patterns CGSS2k+8 and CGSS2k+9 overlap. Furthermore, if the multiple CGS servo patterns CGSS2k+3 to CGSS2K12 are written to the same surface and a portion of the CGS servo patterns CGSS2k+8 and CGSS2k+9 overlap, the data at the intersection of the CGS servo patterns CGSS2k+8 and CGSS2k+9 may be lost because the CGS servo patterns CGSS2k+8 and CGSS2k+9 overlap directly.

[0140] On the other hand, Figure 20 As shown in the EML, when multiple odd-numbered CGS servo patterns CGSS2k+3 to 2k+11 and multiple even-numbered CGS servo patterns CGSS2k+4 to 2k+12 are written to different sides of the disk 10 and a portion of the CGS servo patterns CGSS2k+8 and CGSS2k+9 intersect, it is possible to determine that the order has been reversed. Furthermore, when multiple CGS servo patterns CGSS2k+3 to 2k+12 are written to the same side and a portion of the CGS servo patterns CGSS2k+8 and CGSS2k+9 intersect, the portions of the CGS servo patterns CGSS2k+8 and CGSS2k+9 do not directly intersect, so the data in the intersecting portion of the CGS servo patterns CGSS2k+8 and CGSS2k+9 is not lost. Therefore, by writing the multiple odd-numbered CGS servo patterns CGSS2k+3 to 2k+11 and the multiple even-numbered CGS servo patterns CGSS2k+4 to 2k+12 to different sides of the disk 10, the RRO can be accurately measured.

[0141] The servo pattern control unit 640 writes the FGS servo pattern FGSS, the FS servo pattern FSS, and the product servo pattern PSV onto the disk 10. The servo pattern control unit 640 performs a process of writing the GS servo pattern FGSS and the FS servo pattern FSS (hereinafter sometimes referred to as a post-process of BDW) after the process of writing the initial CGS servo pattern CGSS of the BDW, and performs self-servo writing (SSW) for writing the product servo pattern.

[0142] As a post-BDW process, the servo pattern control unit 640 performs calibration for writing the FGS servo pattern FGSS on the disk 10, reads the CGS servo pattern CGSS for positioning (or tracking), and then writes the FGS servo pattern FGSS onto the disk 10. For example, the servo pattern control unit 640 writes the FGS servo pattern FGSS onto the disk 10 from the outer circumference toward the inner circumference. Alternatively, the servo pattern control unit 640 may write the FGS servo pattern FGSS onto the disk 10 from the inner circumference toward the outer circumference.

[0143] For example, when a plurality of odd-numbered CGS servo patterns CGSS are written to a predetermined surface 10S within a plurality of surfaces 10S of a disk 10, and a plurality of even-numbered CGS servo patterns CGSS are written to a predetermined surface 10S of a plurality of surfaces 10S of the disk 10, the servo pattern control unit 640 uses a plurality of heads 15 to alternately read the plurality of odd-numbered CGS servo patterns CGSS and the plurality of even-numbered CGS servo patterns CGSS, and writes the FGS servo pattern FGSS to the predetermined surface 10S of the disk 10 by positioning (or on track) the plurality of odd-numbered CGS servo patterns CGSS and the plurality of even-numbered CGS servo patterns CGSS.

[0144] For example, when a plurality of odd-numbered CGS servo patterns CGSS are written to more than two surfaces 10S among a plurality of surfaces 10S of the disk 10, and a plurality of even-numbered CG servo patterns CGSS are written to more than two surfaces 10S among a plurality of surfaces 10S of the disk 10, the servo pattern control unit 640 selects one surface from the more than two surfaces 10S on which the plurality of odd-numbered CGS servo patterns CGSS are written, selects one surface from the more than two surfaces 10S on which the plurality of even-numbered CGS servo patterns CGSS are written, uses a plurality of heads 15 to alternately read the plurality of odd-numbered CGS servo patterns CGSS written to the selected surface and the plurality of even-numbered CGS servo patterns CGSS written to the selected surface, and writes the FGS servo pattern FGSS to a predetermined surface 10S of the disk 10 based on positioning (or on track) based on the plurality of odd-numbered CGS servo patterns CGSS written to the selected surface and the plurality of even-numbered CGS servo patterns CGSS written to the selected surface.

[0145] As a post-BDW process, the servo pattern control unit 640 performs calibration for writing the FS servo pattern FSS on the disk 10, reads the FGS servo pattern FGSS for positioning (or tracking), and then writes the FS servo pattern FSS on the disk 10. For example, the servo pattern control unit 640 writes the FS servo pattern FSS on the disk 10 from the inner circumference to the outer circumference. Alternatively, the servo pattern control unit 640 may write the FS servo pattern FSS on the disk 10 from the outer circumference to the inner circumference.

[0146] The servo pattern control unit 640 reads the FS servo pattern FSS, performs positioning (or tracking), and writes the product servo pattern PSV on the disk 10 .

[0147] The positioning control unit 650 performs positioning control of the head 15. The positioning control unit 650 performs positioning control of the head 15 based on the CGS servo pattern CGSS, the FGS servo pattern FGSS, the FS servo pattern FSS, and the product servo pattern PSV. When multiple servo patterns CGSS are arranged for multiple surfaces of the disk 10, the positioning control unit 650 switches between the multiple heads 15 corresponding to each of these surfaces while using all of the multiple servo patterns CGSS arranged for the multiple surfaces of the disk 10 to perform positioning control of the head 15 on one of these surfaces. Furthermore, the positioning control unit 650 performs positioning control of the head 15 based on the actual CGS position, RRO, virtual CGS interval, and actual CGS interval measured by the measurement unit 630.

[0148] Figure 21 This is a flowchart showing an example of BDW according to this embodiment.

[0149] The MPU 60 starts from BDW and executes RampCal ( B2101 ) and velocity calibration ( B2102 ) to write CGS servo patterns to the blank disk 10 , while switching the head 15 and writing multiple CGS servo patterns CGSS to different surfaces of the disk 10 .

[0150] The MPU 60 determines whether the CGS servo pattern CGSS to be written is an odd-numbered CGS servo pattern CGSS or a non-odd-numbered CGS servo pattern CGSS (B2103). In other words, it determines whether the CGS servo pattern CGSS to be written is an odd-numbered CGS servo pattern CGSS or an even-numbered CGS servo pattern CGSS. If the CGS servo pattern CGSS to be written is determined to be an odd-numbered CGS servo pattern CGSS (YES in B2103), the MPU 60 selects a predetermined head 15 corresponding to a predetermined side of the disk 10 (B2104) and proceeds to processing B2106. If the CGS servo pattern CGSS to be written is determined to be a non-odd-numbered CGS servo pattern CGSS, that is, if the CGS servo pattern CGSS to be written is determined to be an even-numbered CGS servo pattern CGSS (NO in B2103), the MPU 60 selects another head 15, different from the predetermined head 15, corresponding to a side of the disk 10 different from the predetermined side (B2105), and proceeds to processing B2106.

[0151] The MPU 60 writes the CGS servo pattern CGSS (B2106). If a CGS servo pattern to be written exists, the process proceeds to B2103. If not, the process proceeds to B2107. The MPU 60 adjusts the Mag of the CGS servo pattern CGSS on each surface to which the CGS servo pattern CGSS was divided and written (B2107).

[0152] The MPU 60 measures the actual CGS position corresponding to the CGS servo pattern CGSS on each surface where the plurality of CGS servo patterns CGSS are divided and written, and calculates a virtual CGS interval and an actual CGS interval based on the actual CGS position (B2108). The virtual CGS interval and the actual CGS interval are recorded in a predetermined recording area, such as the system area 10b of the disk 10, the volatile memory 70, or the non-volatile memory 80 (B2109).

[0153] To write the FGS servo pattern FGSS, the MPU 60 performs calibration based on the imaginary CGS interval and the actual CGS interval (B2110), and writes the FGS servo pattern FGSS based on the CGS servo pattern CGSS (B2111). To write the FS servo pattern FSS, the MPU 60 performs calibration (B2112), and writes the FS servo pattern FSS based on the FGS servo pattern FGSS (B2113).

[0154] According to this embodiment, the magnetic disk device 1 writes a plurality of CGS servo patterns CGSS to different surfaces by dividing them. For example, the magnetic disk device 1 writes two adjacent CGS servo patterns CGSS on the imaginary surface of the disk 10 to different surfaces. Therefore, the magnetic disk device 1 can prevent the two adjacent CGS servo patterns CGSS on the imaginary surface of the disk 10 from being adjacent to or crossing each other. Even if two adjacent CGS servo patterns CGSS on the imaginary surface of the disk 10 cross each other, since these CGS servo patterns CGSS do not cross directly, data will not disappear in the portion where these CGS servo patterns cross each other. Therefore, even if two adjacent CGS servo patterns CGSS on the imaginary surface of the disk 10 cross each other, the magnetic disk device 1 can read these CGS servo patterns CGSS, accurately detect the positions of these CGS servo patterns CGSS, and accurately obtain the RRO corresponding to these CGS servo patterns CGSS. Therefore, the magnetic disk device 1 can improve positioning accuracy. Therefore, the magnetic disk device 1 can improve reliability.

[0155] Next, a magnetic disk device according to a modified example of the first embodiment will be described. In the modified example, the same components as those in the first embodiment are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0156] (Variation 1)

[0157] The magnetic disk device 1 according to the first modification differs from the magnetic disk device 1 according to the first embodiment in the configuration of the R / W channel 40 .

[0158] Figure 22 This is a block diagram showing the configuration of a magnetic disk device according to Modification 1.

[0159] The R / W channel 40 includes a plurality of decoders 410. The plurality of decoders 410 corresponds to the plurality of heads 15. The number of the plurality of decoders 410 is equal to the number of the plurality of heads 15. The plurality of decoders 410 decodes the signals read by the plurality of heads 15, respectively.

[0160] When the measurement unit 630 writes multiple CGS servo patterns CGSS to different surfaces of the disk 10 by dividing them, it is possible not to set switchable areas and non-switchable areas, but to simultaneously read the multiple CGS servo patterns CGSS written to different surfaces of the disk 10 by multiple heads 15 corresponding to different surfaces of the disk 10 to which the multiple CGS servo patterns CGSS are divided and written.

[0161] According to this modification, when the magnetic disk drive 1 writes multiple CGS servo patterns CGSS to different surfaces of the disk 10 by dividing them into sections, it is possible to simultaneously read the multiple CGS servo patterns CGSS written to the different surfaces of the disk 10 using multiple heads 15 corresponding to the different surfaces of the disk 10 to which the multiple CGS servo patterns CGSS are divided, without setting switchable and non-switchable areas. Consequently, the magnetic disk drive 1 can improve positioning accuracy and reliability.

[0162] Several embodiments have been described, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the gist of the invention. These embodiments and their variations are included within the scope and spirit of the invention and are included in the invention described in the claims and their equivalents.

[0163] Label Description

[0164] 1…disk device, 10…disk, 10a…user data area, 10b…system area, 12…spindle motor (SPM), 13…arm, 14…voice coil motor (VCM), 15…head, 15W…write head, 15R…read head, 20…driver IC, 30…head amplifier IC, 40…read / write (R / W) channel, 50…hard disk controller (HDC), 60…microprocessor (MPU), 70…volatile memory, 80…non-volatile memory, 90…buffer memory, 100…host system (host), 130…system controller

Claims

1. A magnetic disk device comprising: a disk having a first surface and a second surface different from the first surface; The first head reads and writes data on the first side; The second head reads and writes data on the second side; a voice coil motor, configured to move the first head and the second head; as well as The controller divides and writes a plurality of spiral patterns to be written on one surface of the disc onto the first surface and the second surface.

2. The magnetic disk device according to claim 1, The controller divides and writes the plurality of spiral patterns onto the first surface and the second surface on which no spiral pattern is written.

3. The magnetic disk device according to claim 1 or 2, The controller controls the first head and the second head to have a constant speed based on a reverse voltage generated by the voice coil motor to write the plurality of spiral patterns.

4. The magnetic disk device according to claim 1 or 2, The controller writes the plurality of spiral patterns alternately on the first surface and the second surface while switching the first head and the second head.

5. The magnetic disk device according to claim 1 or 2, A first spiral pattern among the plurality of spiral patterns and a second spiral pattern among the plurality of spiral patterns written subsequent to the first spiral pattern are written on different surfaces of the disc.

6. The magnetic disk device according to claim 1 or 2, The controller reads the plurality of spiral patterns while switching between the first head and the second head, and positions the first head on the first surface using the plurality of spiral patterns.

7. The magnetic disk device according to claim 6, When the controller determines that a first interval between a third spiral pattern and a fourth spiral pattern adjacent to each other in the plurality of spiral patterns in a top view is equal to or greater than a first threshold, the controller measures the third spiral pattern and the fourth spiral pattern while switching between the first head and the second head.

8. The magnetic disk device according to claim 6, When the controller determines that the first interval between the third and fourth adjacent spiral figures among the multiple spiral figures in a top view is smaller than the first threshold value, the controller uses the first head to measure the third spiral figure in the first week, and after measuring the third spiral figure, uses the second head to measure the fourth spiral figure in the second week.

9. The magnetic disk device according to claim 7, The first threshold value is changed according to the seek direction and speed of the first head and the second head.

10. A method for writing a spiral pattern, applicable to a magnetic disk device, the magnetic disk device comprising: A disk having a first surface and a second surface different from the first surface; a first head for reading data from the first surface and writing data to the first surface; a second head for reading data from the second surface and writing data to the second surface; a voice coil motor for moving the first head and the second head on the first surface and the second surface, wherein the writing method A plurality of spiral patterns to be written on one surface of the disc are divided and written on the first surface and the second surface.

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