magnetic disk drive

Abstract

A magnetic disk device capable of efficiently detecting defects on a disk is provided. [Solution] The magnetic disk device includes a plurality of recording layers L, a plurality of write heads WHD, a plurality of read heads RHD, a selection circuit 3Sb capable of selecting two or more read heads from the plurality of read heads RHD, a read target selection unit 64, a read processing unit 63, and a detection unit 65. When the read target selection unit 64 selects the first recording layer and the second recording layer, the read processing unit 63 controls the driving of the selection circuit 3Sb to cause the selection circuit to select the first read head and the second read head, and simultaneously reads data from the first recording layer and data from the second recording layer, and the detection unit 65 detects the state of the first recording layer and the state of the second recording layer.

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a magnetic disk drive. [Background technology]

[0002] Known magnetic disk devices include conventional magnetic recording (CMR) type (or conventional recording type) magnetic disk devices that write multiple tracks spaced apart in the radial direction of the disk, shingled magnetic recording (SMR) type magnetic disk devices that overwrite multiple tracks in the radial direction of the disk, and hybrid recording type magnetic disk devices that can select between conventional recording type and shingled recording type. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2022-067411 [Patent Document 2] U.S. Patent No. 9,142,246 [Patent Document 3] U.S. Patent No. 8,879,186 [Patent Document 4] Patent No. 5015876 Summary of the Invention [Problem to be solved by the invention]

[0004] This embodiment provides a magnetic disk drive that can efficiently detect defects on the disk. [Means for solving the problem]

[0005] A magnetic disk device according to an embodiment includes: a plurality of recording layers provided on the same or different discs, the plurality of recording layers including a first recording layer and a second recording layer; a plurality of write heads, the plurality of write heads including a first write head that writes data onto the first recording layer and a second write head that writes data onto the second recording layer; a plurality of read heads, the plurality of read heads including a first read head for reading data from the first recording layer and a second read head for reading data from the second recording layer; a selection circuit connected to the plurality of read heads and capable of selecting two or more read heads from the plurality of read heads; a read target selection unit; a read processing unit capable of executing a read process for reading data from each of the recording layers; a detection unit, When the read target selection unit selects the first recording layer and the second recording layer, the read processing section controls driving of the selection circuit, causes the selection circuit to select the first read head and the second read head, and simultaneously reads data from the first recording layer and the second recording layer via the selection circuit; The detection section detects the state of the first recording layer and the state of the second recording layer based on a signal read by the first read head and a signal read by the second read head. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram showing the configuration of a magnetic disk device according to a comparative example. [Figure 2] FIG. 2 is a perspective view showing a part of the magnetic disk device, showing a plurality of disks and a plurality of heads. [Figure 3] FIG. 3 is a schematic diagram showing an example of the arrangement of a plurality of servo areas and a plurality of data areas on one disk according to the comparative example. [Figure 4] FIG. 4 is a schematic diagram showing three tracks in the user data area of ​​the disk shown in FIG. 3 where shingled recording is performed, and a write head. [Figure 5] FIG. 5 is a schematic diagram showing three tracks of the media cache where normal recording processing of the disc shown in FIG. 3 is performed, and the write head. [Figure 6] FIG. 6 is a schematic diagram showing an example of a data write process on a disk. [Figure 7] FIG. 7 is a schematic diagram showing two bands and one guard band in the user data area shown in FIG. [Figure 8] FIG. 8 is a schematic diagram showing three sectors in one track of the band shown in FIG. [Figure 9] FIG. 9 is a schematic diagram showing the two bands and one guard band shown in FIG. 7, and is a diagram for explaining a plurality of target sectors and a plurality of unused sectors. [Figure 10] FIG. 10 is a plan view showing a part of one recording layer and one head according to the comparative example. [Figure 11] FIG. 11 is a circuit diagram showing a selection circuit of the head amplifier IC according to the comparative example. [Figure 12] FIG. 12 is a block diagram showing a partial configuration of the magnetic disk device according to the comparative example, and shows the configuration of the read channel, etc. [Figure 13] FIG. 13 is a block diagram showing the configuration of a magnetic disk device according to an embodiment. [Figure 14] FIG. 14 is a plan view showing a plurality of arms and a plurality of heads according to the embodiment. [Figure 15] FIG. 15 is a plan view showing parts of two recording layers and two heads according to the embodiment, and is a diagram for explaining the positional relationship between the two recording layers and the two heads in the radial direction. [Figure 16] FIG. 16 is a circuit diagram showing a selection circuit of the head amplifier IC according to the above embodiment. [Figure 17] FIG. 17 is a block diagram showing the configuration of a portion of the magnetic disk device according to the above embodiment, and shows the configuration of a read channel different from the read channel shown in FIG. [Figure 18A] Figure 18A is a plan view showing a portion of one recording layer and one head according to the above embodiment, and shows a state in which a write process is being performed to write data to one data track of the above one recording layer using one write head. [Figure 18B] FIG. 18B is a plan view showing a part of another recording layer and another head according to the embodiment, and shows the positional relationship between the another recording layer and the another head during the write process of FIG. 18A. [Figure 19A] Figure 19A is a plan view showing a portion of the other recording layer and the other head according to the embodiment, and shows a state in which a write process is being performed to write data to another data track on the other recording layer using another write head. [Figure 19B] Figure 19B is a plan view showing a portion of the one recording layer and the one head according to the embodiment, and shows the positional relationship between the one recording layer and the one head during the write process of Figure 19A. [Figure 20A] Figure 20A is a plan view showing a portion of the one recording layer and the one head according to the embodiment, and shows a state in which a read process is being performed to read data from the one data track of the one recording layer using one read head. [Figure 20B] Figure 20B is a plan view showing a portion of the other recording layer and the other head according to the embodiment, and shows a state in which a read process is being performed during the read process of Figure 20A, in which data from the other data track of the other recording layer is read using a different read head. [Figure 21]Figure 21 is a diagram showing the state in which a read process is being performed in the above embodiment, in which data from one data track on one recording layer and data from another data track on another recording layer are read simultaneously, and also shows a read gate, and is a diagram for explaining the read process when the timing at which the other read head reaches the specified read position is later than the timing at which the one read head reaches the specified read position. [Figure 22] Figure 22 is a diagram showing the state in which a read process is being performed in the above embodiment, in which data from one data track on one recording layer and data from another data track on another recording layer are simultaneously read, and also shows a read gate, and is a diagram for explaining the read process when the timing at which the other read head reaches a predetermined read position coincides with the timing at which the one read head reaches a predetermined read position. [Figure 23] Figure 23 is a diagram showing the state in which a read process is being performed in the above embodiment, in which data from one data track on one recording layer and data from another data track on another recording layer are simultaneously read, and also shows a read gate, and is a diagram for explaining the read process when the timing at which the other read head reaches the specified read position is earlier than the timing at which the one read head reaches the specified read position. [Figure 24] FIG. 24 is a plan view showing a part of the one recording layer according to the embodiment, showing a state in which a defect detected on the one recording layer straddles six adjacent sectors. [Figure 25] Figure 25 is a plan view showing a portion of one of the recording layers according to the embodiment, and is a diagram showing the state after the track width and sector length of the one of the recording layers have been changed, following Figure 24, in which the defect straddles two adjacent sectors. DETAILED DESCRIPTION OF THE INVENTION

[0007] The magnetic disk device 1 according to the comparative example and the embodiment will be described in detail below with reference to the drawings.

[0008] (Comparative Example) First, the configuration of a magnetic disk device 1 according to a comparative example will be described. Fig. 1 is a block diagram showing the configuration of the magnetic disk device 1 according to the comparative example. In this comparative example, the magnetic disk device 1 is a hybrid recording type magnetic disk device that selects and executes a normal recording type and a shingled recording type. However, the technology described below may be applied to a shingled recording type magnetic disk device or a normal recording type magnetic disk device.

[0009] 1, the magnetic disk device 1 includes a plurality of, for example, 1 to 10 disks (magnetic disks) DK as recording media, a spindle motor (SPM) 20 as a drive motor, a head stack assembly 22, a driver IC 120, a head amplifier integrated circuit (hereinafter referred to as head amplifier IC) 130, a volatile memory 70, a buffer memory (buffer) 80, a nonvolatile memory 90, and a system controller 110 which is a one-chip integrated circuit. The magnetic disk device 1 is also connected to a host system (hereinafter simply referred to as host) 100.

[0010] Each disk DK is formed to have a diameter of, for example, 97 mm (3.8 inches) and has a recording layer (magnetic recording layer) on both sides. In this comparative example, the magnetic disk device 1 is equipped with 1 to 11 disks DK, but the number of disks DK is not limited to these.

[0011] The head stack assembly 22 can control the movement of the head HD mounted on the arm 30 to a target position on the disk DK, i.e., can seek, by driving the voice coil motor (hereinafter referred to as VCM) 24. The VCM 24 functions as an actuator. The disk DK has a user data area U that can be used by the user and a system area S in which information required for system management is written, as areas where data can be written.

[0012] The head HD records and reproduces information on the disk DK. The head HD has a slider as its main body, and is equipped with a write head WHD and a read head RHD mounted on the slider. The write head WHD writes data to the recording layer of the disk DK. The read head RHD reads data from the data tracks on the recording layer of the disk DK.

[0013] The "center of the head HD" may be referred to as the "head HD", the "center of the write head WHD" may be referred to as the "write head WHD", and the "center of the read head RHD" may be referred to as the "read head RHD". The "center of the write head WHD" may be simply referred to as the "head HD", and the "center of the read head RHD" may be simply referred to as the "head HD".

[0014] The driver IC 120, under the control of the system controller 110 (more specifically, the MPU 60 described later), controls the driving of the SPM 20 and VCM 24. The SPM 20 supports and rotates a plurality of discs DK.

[0015] The head amplifier IC 130 includes a selection circuit 3Sa, a read amplifier 3R1, a read amplifier 3R2, and a write driver 3W. The read amplifier 3R1 and the read amplifier 3R2 are each a preamplifier that amplifies a read signal read from the disk DK and outputs the amplified signal to the system controller 110 (more specifically, a read / write (R / W) channel 140, which will be described later). The write driver 3W outputs a write current to the head HD according to the signal output from the R / W channel 140.

[0016] The volatile memory 70 is a semiconductor memory in which stored data is lost when the power supply is cut off. The volatile memory 70 stores data and the like required for processing in each section of the magnetic disk device 1. The volatile memory 70 is a random access memory (RAM). The volatile memory 70 is, for example, a dynamic random access memory (DRAM). However, the volatile memory 70 may also be a synchronous dynamic random access memory (SDRAM).

[0017] The buffer memory 80 is a semiconductor memory that temporarily records data and the like transmitted and received between the magnetic disk device 1 and the host 100. The buffer memory 80 may be configured integrally with the volatile memory 70. The buffer memory 80 is a volatile RAM. For example, the buffer memory 80 is a DRAM, an SRAM (Static Random Access Memory), an SDRAM, an FeRAM (Ferroelectric Random Access Memory), an MRAM (Magnetoresistive Random Access Memory), or the like. The buffer memory 80 includes areas used as a read cache and a write cache, and temporarily stores commands received from the host 100 .

[0018] The nonvolatile memory 90 is a semiconductor memory that records stored data even when the power supply is cut off. The nonvolatile memory 90 is, for example, a NAND-type flash read only memory (FROM). However, the nonvolatile memory 90 may also be a NOR-type FROM.

[0019] The system controller (controller) 110 is realized, for example, using a large-scale integrated circuit (LSI) called a system-on-a-chip (SoC), in which multiple elements are integrated on a single chip. The system controller 110 includes a read / write (R / W) channel 140, a hard disk controller (HDC) 150, and a microprocessor (MPU) 60. The system controller 110 is electrically connected to a driver IC 120, a head amplifier IC 130, a volatile memory 70, a buffer memory 80, a non-volatile memory 90, and a host 100.

[0020] The R / W channel 140 performs signal processing of read data transferred from the disk DK to the host 100 and write data transferred from the host 100 in response to instructions from the MPU 60 (described later). The R / W channel 140 has a circuit or function for modulating write data. The R / W channel 140 also has a circuit or function for measuring the signal quality of the read data. The R / W channel 140 is electrically connected to, for example, the head amplifier IC 130, the HDC 150, the MPU 60, etc.

[0021] The HDC 150 controls data transfer between the host 100 and the R / W channel 140 in response to instructions from the MPU 60, which will be described later. The HDC 150 is electrically connected to, for example, the R / W channel 140, the MPU 60, the volatile memory 70, the buffer memory 80, the non-volatile memory 90, and the like.

[0022] The HDC 150 has a gate generation unit 151. The gate generation unit 151 generates various gates, such as write gates, read gates, and servo gates, in response to commands from the host 100 and instructions from the MPU 60, and outputs them to the R / W channel 140, for example, to the gate detection unit 14D. Hereinafter, "raising a specific gate" may also be referred to as "asserting a specific gate." Furthermore, "lowering a specific gate" may also be referred to as "negating a specific gate." "Asserting a specific gate" and "negating a specific gate" may also include the meaning of "generating a specific gate." The gate generation unit 151 may be included in the R / W channel 140 or the MPU 60.

[0023] The R / W channel 140 has a gate detection unit 14D. The gate detection unit 14D detects whether various gates, such as a write gate, a read gate, and a servo gate, are in an asserted state or a negated state. For example, the gate detection unit 14D executes the write process when it detects that the write gate is asserted, and pauses (stops) the write process when it detects that the write gate is negated. In addition, the gate detector 14D executes a read process when it detects that the read gate is asserted, and stops the read process when it detects that the read gate is negated. The gate detector 14D executes a servo read process when it detects that the servo gate is asserted, and stops the servo read process when it detects that the servo gate is negated. The gate detector 14D may be located within the HDC 150 or the MPU 60.

[0024] The MPU 60 is a control unit and a main controller that controls each unit of the magnetic disk device 1. The MPU 60 controls the VCM 24 via the driver IC 120 and executes servo control to position the head HD. The MPU 60 controls the operation of writing data to the disk DK and selects a destination for write data transferred from the host 100. The MPU 60 also controls the operation of reading data from the disk DK and controls the processing of read data transferred from the disk DK to the host 100. The MPU 60 is connected to each unit of the magnetic disk device 1. The MPU 60 is electrically connected to, for example, the driver IC 120, the R / W channel 140, the HDC 150, etc.

[0025] The MPU 60 includes a read / write processing unit 61, a read target selection unit 64, a detection unit 65, a management unit 66, etc. The MPU 60 executes the processing of each of these units, such as the read / write processing unit 61, the read target selection unit 64, the detection unit 65, and the management unit 66, on firmware. Note that the MPU 60 may include each of these units as a circuit.

[0026] The read / write processing unit 61 has a write processing unit 62 and a read processing unit 63. In accordance with commands from the host 100, the write processing unit 62 controls data write processing, and the read processing unit 63 controls data read processing, causing the read head RHD to read data from the disk DK. The write processing unit 62 can execute write processing to write data to each recording layer of the disk DK. The read / write processing unit 61 controls the VCM 24 via the driver IC 120, positions the head HD to a target position (predetermined radial position) on the disk DK, and executes read processing or write processing.

[0027] FIG. 2 is a perspective view showing a part of the magnetic disk device 1, and shows a plurality of disks DK and a plurality of heads HD. As shown in Fig. 2, the direction in which the disk DK rotates in the circumferential direction is referred to as the rotation direction d3. Note that in the example shown in Fig. 2, the rotation direction d3 is shown counterclockwise, but it may be the opposite direction (clockwise). Also, the movement direction d2 of the head HD relative to the disk DK is opposite to the rotation direction d3. The movement direction d2 is the direction in which the head HD sequentially writes and reads data to and from the disk DK in the circumferential direction, that is, the direction in which the head HD moves relative to the disk DK in the circumferential direction.

[0028] The magnetic disk device 1 includes f disks DK1 to DKf and g heads HD1 to HDg. In this comparative example, the number of heads HD is twice the number of disks DK (g=2×f). The disks DK1 to DKf are arranged coaxially and stacked with a gap between them. The disks DK1 to DKf have the same diameter. Here, terms such as "same," "identical," "matched," and "equivalent" not only mean exactly the same, but also mean different enough to be considered substantially the same. The diameters of the disks DK1 to DKf may be different from each other.

[0029] Each disc DK has a recording layer L on both sides. The multiple recording layers L are provided on the same or different discs DK. For example, disc DK1 has a first recording layer La1 and a second recording layer Lb1 opposite the first recording layer La1. Disc DK2 has a first recording layer La2 and a second recording layer Lb2 opposite the first recording layer La2. Disc DKi has a first recording layer Lai and a second recording layer Lbi opposite the first recording layer Lai. Each first recording layer La may also be referred to as a front surface or recording surface. Each second recording layer Lb may also be referred to as a back surface or recording surface. However, each first recording layer La may also be referred to as the back side, and in this case, each second recording layer Lb may also be referred to as the front side.

[0030] Each recording layer L has a user data area U and a system area S. The first recording layer La1 has a user data area Ua1 and a system area Sa1. The second recording layer Lb1 has a user data area Ub1 and a system area Sb1. The first recording layer La2 has a user data area Ua2 and a system area Sa2. The second recording layer Lb2 has a user data area Ub2 and a system area Sb2. The first recording layer Laf has a user data area Uaf and a system area Saf. The second recording layer Lbf has a user data area Ubf and a system area Sbf.

[0031] In the user data area Ua1 (first recording layer La1), the track sandwiched between the double dashed lines in the figure is called track Ta1. In the user data area Ub1 (second recording layer Lb1), the track located on the opposite side of track Ta1 is called track Tb1. In the user data area Ua2 (first recording layer La2), the track sandwiched between the double dashed lines in the figure is called track Tc1, and in the user data area Ub2 (second recording layer Lb2), the track located on the opposite side of track Tc1 is called track Td1. In the user data area Uaf (first recording layer Laf), the track sandwiched between the double dashed lines in the figure is called track Te1. In the user data area Ubf (second recording layer Lbf), the track located on the opposite side of track Te1 is called track Tf1.

[0032] In this comparative example, tracks Ta1, Tb1, Tc1, Td1, Te1, and Tf1 are located on the same cylinder. However, tracks Ta1, Tb1, Tc1, Td1, Te1, and Tf1 do not have to be located on the same cylinder. In that case, tracks Ta1, Tb1, Tc1, Td1, Te1, and Tf1 may be positioned with a radial offset d1.

[0033] The head HD faces the disk DK. In this comparative example, one head HD faces each recording layer L of the disk DK. For example, head HD1 faces the first recording layer La1 of the disk DK1, writes data to the first recording layer La1, and reads data from the first recording layer La1. Head HD2 faces the second recording layer Lb1 of the disk DK1, writes data to the second recording layer Lb1, and reads data from the second recording layer Lb1.

[0034] Head HD3 faces the first recording layer La2 of disk DK2 and writes data to and reads data from the first recording layer La2. Head HD4 faces the second recording layer Lb2 of disk DK2 and writes data to and reads data from the second recording layer Lb2. Head HDg-1 faces the first recording layer Laf of disk DKf and writes data to and reads data from the first recording layer Laf. Head HDg faces the second recording layer Lbf of disk DKf and writes data to and reads data from the second recording layer Lbf.

[0035] 3 is a schematic diagram showing an example of the arrangement of a plurality of servo areas SV and a plurality of data areas DTR on one disk DK according to this comparative example. As shown in FIG. 3, in the radial direction d1 of the disk DK, the direction toward the outer periphery of the disk DK is referred to as the outward direction (outside), and the direction opposite to the outward direction is referred to as the inward direction (inside). In FIG. 3, the user data area U is divided into an inner area IR located inward, an outer area OR located outward, and a middle area MR located between the inner area IR and the outer area OR.

[0036] The disk DK has a plurality of servo areas SV and a plurality of data areas DTR. The plurality of servo areas SV may, for example, extend radially in the radial direction d1 of the disk DK and be discretely arranged at predetermined intervals in the circumferential direction. The plurality of servo areas SV may, for example, extend linearly from the inner circumference to the outer circumference and be discretely arranged at predetermined intervals in the circumferential direction. The plurality of servo areas SV may, for example, extend spirally from the inner circumference to the outer circumference and be discretely arranged at predetermined intervals in the circumferential direction. Furthermore, the plurality of servo areas SV may, for example, be arranged in an island-like manner in the radial direction d1 and be discretely arranged at predetermined intervals in the circumferential direction.

[0037] Hereinafter, one servo area SV in a given track may be referred to as a "servo sector." Note that a "servo area SV" may also be referred to as a "servo sector SV." A servo sector contains servo data. Hereinafter, "the arrangement of several servo data that make up a servo sector" may also be referred to as a "servo pattern." Note that "servo data written in a servo sector" may also be referred to as a "servo sector."

[0038] Each of the multiple data areas DTR is disposed between multiple servo areas SV. For example, a data area DTR corresponds to an area between two consecutive servo areas SV in the circumferential direction. Hereinafter, one data area DTR in a given track may be referred to as a "data sector." Note that a "data area DTR" may also be referred to as a "data sector DTR." A data sector contains user data. Note that "user data written to a data sector" may also be referred to as a "data sector." A "data sector" may also be referred to as "user data." Also, a "pattern composed of several pieces of data" may also be referred to as a "data pattern." In the example shown in FIG. 3, the data pattern of a given track is composed of multiple servo data (servo sectors) and multiple user data (data sectors).

[0039] The servo area SV has a plurality of zone servo areas ZSV, etc. In addition to the zone servo areas ZSV, the servo area SV may also include an area including a gap (a deviation in the circumferential position of two zone servo areas), an area including servo data, and a data area DTR, etc. The plurality of zone servo areas ZSV are discretely arranged along the radial direction d1. Each of the plurality of zone servo areas ZSV extends in the radial direction d1.

[0040] One zone servo area (servo area) ZSV in a specified track may be referred to as a "zone servo sector" or "servo sector." Note that a "zone servo area (servo area) ZSV" may also be referred to as a "zone servo sector ZSV" or "servo sector ZSV." "Servo data written in a zone servo sector" may also be referred to as a "zone servo sector" or "servo sector." Hereinafter, "the arrangement of several servo data constituting a zone servo sector" may also be referred to as a "zone servo pattern" or "servo pattern." Hereinafter, one servo area SV in a specified track may also be referred to as a "zone pattern sector."

[0041] Note that a "servo area SV" may also be referred to as a "zone pattern sector." "At least one piece of data, etc. written to a zone pattern sector" may also be referred to as a "zone pattern sector." A zone pattern sector includes at least one zone servo sector. Hereinafter, "data pattern of a zone pattern sector" may also be referred to as a "zone data pattern."

[0042] 3, the servo area SV has zone servo areas ZSV0, ZSV1, and ZSV2. The zone servo areas ZSV0, ZSV1, and ZSV2 are arranged in a staggered manner in the radial direction d1. The zone servo areas ZSV0, ZSV1, and ZSV2 may also be arranged in a stepped manner in the radial direction d1.

[0043] Zone servo area ZSV2 is located closer to the inner periphery than zone servo area ZSV1. Zone servo area ZSV0 is located closer to the outer periphery than zone servo area ZSV1. For example, zone servo area ZSV2 is arranged from inner area IR to middle area MR, zone servo area ZSV1 is arranged from inner area IR to outer area OR, and zone servo area ZSV0 is arranged from middle area MR to outer area OR. Hereinafter, in a given servo area SV, a given radial area in which multiple zone servo areas ZSV are arranged in the circumferential direction may also be referred to as a zone servo boundary area, a double servo area, or a double zone servo area ZB.

[0044] In the example shown in Fig. 3, the primary servo areas SVO and the secondary servo areas SVE are alternately arranged at intervals in the circumferential direction. For example, one secondary servo area SVE is arranged between two primary servo areas SVO that are consecutively arranged at an interval in the circumferential direction. In other words, one secondary servo area SVE is arranged between two primary servo areas SVO that are consecutively arranged at an interval in the circumferential direction. For example, if consecutive numbers are assigned to all the servo areas SV of the disk DK in order, the primary servo areas SVO correspond to the odd-numbered servo areas SV, and the secondary servo areas SVE correspond to the even-numbered servo areas SV. Note that two or more secondary servo areas SVE may be arranged between two primary servo areas SVO that are consecutively arranged at an interval in the circumferential direction.

[0045] The primary servo area SVO and the secondary servo area SVE may be, for example, composed only of a servo area (hereinafter sometimes referred to as a normal servo area) that reads and demodulates servo data as a whole. Hereinafter, "reading and demodulating servo data" may also be referred to as "servo reading." The primary servo area SVO and the secondary servo area SVE may be, for example, composed of a normal servo area and a servo area (hereinafter sometimes referred to as a short servo area) that servo reads a circumferential range of servo data that is smaller than the circumferential range of servo data servo read in the normal servo area.

[0046] The media cache M is allocated to the disk DK. However, the media cache M does not have to be located on the disk DK. By using the above-mentioned plurality of servo data, for example, it is possible to derive the positioning error of the head HD (for example, the write head WHD).

[0047] In the explanation of this comparative example, the disk DK has three zones, but the number of zones on the disk DK can be changed in various ways. The number of zones on the disk DK may be 30 to 40. Furthermore, each zone has multiple bands. For example, each zone may have several hundred bands.

[0048] 4 is a schematic diagram showing the write head WHD and three tracks STR in the user data area U where shingled recording is performed on the disk DK shown in FIG. 3. The user data area U is a shingled recording area. Within the user data area U, it is permitted to write data sequentially in band units, that is, shingled recording is permitted.

[0049] As shown in Fig. 4, the write head WHD can sequentially write data to the disk DK in the travel direction d2. The read head RHD shown in Fig. 3 can also sequentially read data written to the disk DK in the travel direction d2.

[0050] The direction in which a plurality of tracks STR, which are a plurality of data tracks, are continuously shingled-recorded in a direction parallel to the radial direction d1, that is, the direction in which the next track STR to be written is overlapped on the track STR written one before in the radial direction d1, is called the overwrite direction or recording progress direction. In the band BAe shown in Figure 4, the overwrite direction d5 is an inward direction, but the overwrite direction may also be an outward direction. For example, the overwrite direction applied to multiple bands BA (multiple zones Z) located on the outer side of a specific radial position may be opposite to the overwrite direction applied to multiple bands BA (multiple zones Z) located on the inner side of the specific radial position.

[0051] Band BAe has a plurality of tracks STR, including tracks STRe, STRe+1, and STRe+2. Tracks STRe, STRe+1, and STRe+2 are continuously overwritten in the order shown in the overwrite direction d5. Of tracks STRe, STRe+1, and STRe+2, track STRe corresponds to the track onto which data is written first, and track STRe+2 corresponds to the track onto which data is written last.

[0052] Track STRe has a track center STCe at the center in the radial direction d1 when no other tracks have been overwritten. Track STRe+1 has a track center STCe+1 at the center in the radial direction d1 when no other tracks have been overwritten. Track STRe+2 has a track center STCe+2 at the center in the radial direction d1 when no other tracks have been overwritten.

[0053] In the example shown in Figure 4, tracks STRe, STRe+1, and STRe+2 are written at a pitch (shingled recording track pitch) STP. The track center STCe of track STRe and the track center STCe+1 of track STRe+1 are spaced apart in the radial direction d1 by a pitch STP. The track center STCe+1 of track STRe+1 and the track center STCe+2 of track STRe+2 are spaced apart in the radial direction d1 by a pitch STP. Tracks STRe to STRe+2 may be written at different pitches.

[0054] The width in the radial direction d1 of the area of ​​track STRe where track STRe+1 is not overwritten is the same as the width in the radial direction d1 of the area of ​​track STRe+1 where track STRe+2 is not overwritten. Note that the width in the radial direction d1 of the area of ​​track STRe where track STRe+1 is not overwritten may be different from the width in the radial direction d1 of the area of ​​track STRe+1 where track STRe+2 is not overwritten.

[0055] In Fig. 4, for convenience of explanation, each track STR is shown as a rectangle, but in reality, each track STR is curved along the circumferential direction. Also, each track STR may be wavy, extending in the circumferential direction while fluctuating in the radial direction d1. Note that in Fig. 4, three tracks STR are overwritten, but two tracks STR may be overwritten, or more than three tracks STR may be overwritten.

[0056] The write processing unit 62 selects a shingled recording format in which data is written to multiple tracks STR in an overwrite direction d5, and causes the write head WHD to write data to each band BA. In the example shown in Fig. 4, the write processing unit 62 sequentially shingles data on tracks STRe to STRe+2 in band BAe inward (in the overwrite direction d5) at a pitch STP. Since data is written to the user data area U using the shingled recording format, the recording density of the user data area U can be improved.

[0057] The write processing unit 62 writes track STRe+1 inward from track STRe at pitch STP, and overwrites track STRe+1 on a part of the inner circumference side of track STRe. The write processing unit 62 writes track STRe+2 inward from track STRe+1 at pitch STP, and overwrites track STRe+2 on a part of the inner circumference side of track STRe+1.

[0058] Figure 5 is a schematic diagram showing the three tracks CTR and the write head WHD of the media cache M where normal recording processing of the disk DK shown in Figure 3 is performed. The media cache M and the system area S shown in Figure 3 are normal recording areas. Random data writing is permitted in the media cache M and the system area S, that is, normal recording is permitted.

[0059] 5, the media cache M has a plurality of tracks CTR including tracks CTRe, CTRe+1, and CTRe+2. Each of the plurality of tracks CTR is a data track. For example, the width in the radial direction d1 (track width) of the tracks CTRe, CTRe+1, and CTRe+2 is the same. Note that the track widths of the tracks CTRe to CTRe+2 may be different from each other.

[0060] Track CTRe has a track center CTCe at the center in the radial direction d1, track CTRe+1 has a track center CTCe+1 at the center in the radial direction d1, and track CTRe+2 has a track center CTCe+2 at the center in the radial direction d1. In the example shown in Fig. 5, tracks CTRe, CTRe+1, and CTRe+2 are written at a pitch (normal recording track pitch) CTP. The track center CTCe of track CTRe and the track center CTCe+1 of track CTRe+1 are separated by the pitch CTP. The track center CTCe+1 of track CTRe+1 and the track center CTCe+2 of track CTRe+2 are separated by the pitch CTP.

[0061] The tracks CTRe and CTRe+1 are separated by a gap GP. The tracks CTRe+1 and CTRe+2 are separated by a gap GP. The tracks CTRe to CTRe+2 may be written at different pitches. For ease of explanation, each track CTR is shown as a rectangle in FIG. 5, but in reality, each track CTR is curved along the circumferential direction. Furthermore, each track CTR may be wavy, extending in the circumferential direction while fluctuating in the radial direction d1.

[0062] The write processing unit 62 can select a normal recording format in which data is written to a plurality of tracks CTR at intervals in the radial direction d1 of the disk DK and perform the write processing. In the example shown in Figure 5, the write processing unit 62 positions the write head WHD at the track center CTCe in a predetermined area of ​​the disk DK and performs normal recording on the track CTRe or a predetermined sector of the track CTRe.

[0063] The write processing unit 62 positions the write head WHD at a track center CTCe+1 that is spaced inward from the track center CTCe of the track CTRe by the pitch CTP, and performs normal recording on the track CTRe+1 or a predetermined sector of the track CTRe+1. The write processing unit 62 positions the write head WHD at a track center CTCe+2 that is spaced inward from the track center CTCe+1 of the track CTRe+1 by the pitch CTP, and performs normal recording on the track CTRe+2 or a predetermined sector of the track CTRe+2.

[0064] The write processing unit 62 may normally record tracks CTRe, CTRe+1, and CTRe+2 sequentially in a predetermined area of ​​the disk DK, or may normally record randomly in a predetermined sector of track CTRe, a predetermined sector of track CTRe+1, and a predetermined sector of track CTRe+2.

[0065] 6 is a schematic diagram showing an example of data write processing on a disk DK. Tracks STR and CTR are data tracks. As shown in FIG. 6, the user data area U has bands BAa, BAb, and BAc. Bands BAa, BAb, and BAc belong to the same zone Ze. In zone Ze, bands BAa, BAb, and BAc are arranged intermittently in the overwrite direction d5 in the order shown.

[0066] Bands BAa and BAb are adjacent to each other in the radial direction d1, and bands BAb and BAc are adjacent to each other in the radial direction d1. Band BAa includes x tracks: STRa0, STRa1, STRa2, ..., STRa(x-3), STRa(x-2), and STRa(x-1). Tracks STRa0 to STRa(x-1) are shingled recorded in the order listed in the overwrite direction d5. In band BAa, track STRa0 corresponds to the first track onto which data is written first, and track STRa(x-1) corresponds to the last track onto which data is written last.

[0067] Band BAb includes x tracks: STRb0, STRb1, STRb2, ..., STRb(x-3), STRb(x-2), and STRb(x-1). Tracks STRb0 to STRb(x-1) are shingled recorded in the order listed in the overwrite direction d5. In band BAb, track STRb0 corresponds to the first track onto which data is written first, and track STRb(x-1) corresponds to the last track onto which data is written last.

[0068] Band BAc includes x tracks: STRc0, STRc1, STRc2, ..., STRc(x-3), STRc(x-2), and STRc(x-1). Tracks STRc0 to STRc(x-1) are shingled recorded in the order listed in the overwrite direction d5. In band BAc, track STRc0 corresponds to the first track onto which data is written first, and track STRc(x-1) corresponds to the last track onto which data is written last.

[0069] Each band BA belonging to the same zone Z has the same number of tracks STR. For example, each band BA belonging to zone Ze has the same number of tracks STR. In other words, the number of tracks STR that a band BA has is fixed for each zone Z. In this example, the number of tracks STR that each band BA belonging to zone Ze has is x.

[0070] Fig. 6 shows tracks CTR(x-2) and CTR(x-1). In Fig. 6, tracks CTR(x-2) and CTR(x-1) are usually recorded in the media cache M or the system area S. Tracks CTR(x-2) and CTR(x-1) are adjacent to each other in the radial direction d1.

[0071] Fig. 7 is a schematic diagram showing two bands BAa and BAb and one guard band GB in the user data area U shown in Fig. 6. As shown in Fig. 7, the shingled recording method differs from the normal recording method in that part of the track STR is overwritten, and therefore the MPU 60 manages the track group in the user data area U in units called bands.

[0072] A guard band GB is generally provided between bands BA adjacent in the radial direction d1. The guard band GB includes a guard track GTR. Unlike this comparative example, the guard band GB may include multiple guard tracks GTR. The guard band GB has the role of suppressing interference between adjacent bands BA. The guard band GB makes it possible to perform shingled recording in units of one band BA. Furthermore, the guard band GB makes it possible to separate the ranges (bands BA) to be written sequentially.

[0073] For example, the track center STCa(x-3) of track STRa(x-3), the track center STCa(x-2) of track STRa(x-2), the track center STCa(x-1) of track STRa(x-1), the track center GTC of the guard track GTR, the track center STCb0 of track STRb0, the track center STCb1 of track STRb1, and the track center STCb2 of track STRb2 are positioned at equal pitches in the overwrite direction d5.

[0074] Excluding the guard band GB, the recording capacity of each band BA in the user data area U is usually determined in advance based on the user's required specifications. The MPU 60 can record the same amount of data in each band BA. Typically, the recording capacity of each band BA is 128 MiB or 256 MiB.

[0075] 8 is a schematic diagram showing three sectors SCe, SC(e+1), and SC(e+2) of one track STRa0 of band BAa shown in FIG. 6. As shown in FIG. 8, each track STR has a plurality of sectors SC arranged in the circumferential direction. Track STRa1 has a plurality of sectors SC including sectors SCe, SC(e+1), and SC(e+2). Each track STR belonging to the same zone Z has the same number of sectors SC. In this comparative example, each track STR belonging to zone Ze has y sectors SC.

[0076] Each sector SC has a length Ls in the circumferential direction of the disk DK. Each sector SC may be a split sector separated by a servo sector SV. In this case, the length of the sector SC does not have to be Ls. The write head WHD is a magnetic head for energy-assisted recording (EAMR) that performs energy-assisted magnetic recording. In this comparative example, the write head WHD is configured to use energy other than magnetic energy, but this is not limiting, and the write head WHD may be a magnetic head that is not configured to perform energy-assisted recording.

[0077] FIG. 9 is a schematic diagram showing the two bands BAa and BAb and one guard band GB shown in FIG. 7, and is a diagram for explaining a plurality of target sectors RSC and a plurality of unused sectors VSC. 9, for the sake of convenience, each track STR is shown as a rectangle, but in reality, each track STR is curved along the circumferential direction. Furthermore, although multiple tracks STR are arranged in the overwrite direction d5 without overlapping, in reality, multiple tracks STR are arranged in the overwrite direction d5 while overlapping. Furthermore, in the figure, target sectors RSC are marked with a dot pattern, and unused sectors NSC are marked with a grid pattern. Unused sectors VSC are shown as solid.

[0078] As shown in Figure 9, the band number of band BAa is "a" and the band number of band BAb is "b". The track numbers of each band BA are "0" to "x-1". The sector numbers of each track STR are "0" to "y-1". Hereinafter, sector SC of each band BA may be identified using the following symbol: "SC (track number, sector number)".

[0079] In this comparative example, band BAa is a band adjacent to band BAb, and is a band located to the right of band BAb in the overwriting direction d5. Each track STR in band BAa contains G target sectors RSC (one or more target sectors RSC) in which valid data is written. For example, track STRa0 has y target sectors RSC (G=y). All sectors SC in track STRa0 are target sectors RSC. Track STRa(x-1) has five target sectors RSC (G=5). The remaining sectors SC in track STRa(x-1) are unused sectors VSC in which valid data is not written. From the above, the number of target sectors RSC in track STRa0 is different from the number of target sectors RSC in track STRa(x-1).

[0080] In band BAb, in two tracks STR, numbered 0 and 1, sector SC numbered 4 is a defective sector and an unused sector NSC. Sectors SC numbered 0 to 3 and 5 to y-1 are target sectors RSC and recording sectors USC. All sectors SC in tracks 2 through x-2 of STR are target sectors RSC and recording sectors USC. In track STR x-1 of band BAb, seven sectors SC from 0 through 6 are target sectors RSC and recording sectors USC. Meanwhile, in track STR x-1 of band BAb, the remaining sectors SC from 7 through y-1 are unused sectors VSC to which no valid data has been written.

[0081] FIG. 10 is a plan view showing a part of one recording layer Lm and one head HDm according to this comparative example. 10, the head HDm facing the recording layer Lm has a write head WHDm, a read head RHDm1, and a read head RHDm2. The write head WHDm, the read head RHDm1, and the read head RHDm2 are supported by the same arm 30.

[0082] During a period in which data is written to track STRi on recording layer Lm using write head WHDm, a first offset amount, which is the distance from write head WHDm to read head RHDm1 in the first direction da, is defined as Cm. When writing data to track STRi using write head WHDm, the write processing unit 62 offsets read head RHDm1 by Cm in the first direction da from the position of track STRi, positions write head WHDm opposite track STRi, and writes user data to track STRi using write head WHDm.

[0083] The first offset amount Cm depends on the Yaw angle, which is the tilt angle of the head HDm with respect to the circumferential direction of the recording layer Lm. The first offset amount Cm may be common to each band BA or each zone Z.

[0084] FIG. 11 is a circuit diagram showing a selection circuit 3Sa of a head amplifier IC 130 according to this comparative example. 11, the selection circuit 3Sa is a multiplexer that receives many signals and outputs six signals. The selection circuit 3Sa can connect to one head HD at a time among the heads HD1 to HDg. In this example, the selection circuit 3Sa is connected to the head HD2.

[0085] Of the terminals of the selection circuit 3Sa on the head HD2 side, the positive terminal R1P and negative terminal R1N are connected to the read head RHD21 of the head HD2. The positive terminal R1P2 and negative terminal R1N2 are connected to the read head RHD22 of the head HD2. The positive terminal W1P and negative terminal W1N are connected to the write head WHD2 of the head HD2.

[0086] Of the terminals of the selection circuit 3Sa on the R / W channel 140 side, the positive terminal RDP and the negative terminal RDN are connected to the read amplifier 3R1. The positive terminal RDP2 and the negative terminal RDN2 are connected to the read amplifier 3R2. The positive terminal WDP and the negative terminal WDN are connected to the write driver 3W.

[0087] The read signal output by the read head RHD is an differential signal and is a pair of signals. The write head WHD operates using the differential signal, and the write signal input to the write head WHD is a pair of signals. By using such a differential signal, signals can be transmitted at high speed and without noise. Here, the differential signal is mentioned to explain the difference between the level of the positive signal and the level of the negative signal. However, in the following explanation, the pair of signals output by the read head RHD may be collectively referred to as a read signal, and the pair of signals input to the write head WHD may be collectively referred to as a write signal.

[0088] FIG. 12 is a block diagram showing a partial configuration of the magnetic disk device 1 according to this comparative example, and shows the configuration of the read channel 14R1 and the like. 12, the read channel 14R1 of the R / W channel 140 is connected to the head amplifier IC 130 and includes a processing circuit 4PC for two-dimensional magnetic recording (TDMR) technology. The processing circuit 4PC includes low-pass filters (LPFs) 4R1a and 4R1b, analog-to-digital converters (ADCs) 4R2a and 4R2b, a two-dimensional FIR (Finite Impulse Response) filter 4R3, a Viterbi decoder 4R4, and an LDPC (Low Density Parity Check) decoder 4R5.

[0089] Here, the recording layer Lm has tracks STRi. The write processing unit 62 can write user data to the tracks STRi using the write head WHDm.

[0090] The LPF4R1a is connected to the read head RHDm1 of the head HDm via the read amplifier 3R1 of the head amplifier IC 130. The LPF4R1a can remove noise contained in the first read signal read by the read head RHDm1 and amplified by the read amplifier 3R1. The ADC4R2a is connected to the LPF4R1a and can convert the first read signal into a digital signal.

[0091] LPF4R1b is connected to the read head RHDm2 of the head HDm via the read amplifier 3R2 of the head amplifier IC 130. LPF4R1b can remove noise contained in the second read signal that is read by the read head RHDm2 and amplified by the read amplifier 3R2. ADC4R2b is connected to LPF4R1b and can convert the second read signal into a digital signal.

[0092] The two-dimensional FIR filter 4R3 is connected to the ADCs 4R2a and 4R2b. The two-dimensional FIR filter 4R3 performs waveform equalization processing to equalize the waveform of composite data obtained by combining a first read signal read by the read head RHDm1 and a second read signal read by the read head RHDm2, so as to minimize the error rate (BER) of the data written to the track STRi, and can output waveform equalized data that is the result of performing the waveform equalization processing on the composite data.

[0093] The Viterbi decoder 4R4 is connected to the two-dimensional FIR filter 4R3. Waveform equalization data is input to the Viterbi decoder 4R4. The Viterbi decoder 4R4 can output decoded data obtained by decoding the waveform equalization data. The internal calculations of the Viterbi decoder 4R4 can be performed using an algorithm that takes into account the track STRi. The signal average value, noise variance value, and tap coefficients of the noise whitening filter in the metric calculations of the Viterbi decoder 4R4 are provided for each path metric that takes into account the track STRi, and are optimized to minimize the BER of the track STRi.

[0094] The LDPC decoder 4R5 is connected to the Viterbi decoder 4R4. The LDPC decoder 4R5 can perform LDPC code decoding processing on the decoded data input from the Viterbi decoder 4R4.

[0095] When the read target selection unit 64 selects track STRi on recording layer Lm, the read processing unit 63 drives the actuator (VCM 24), controls the seek operation of head HDm (read head RHDm1 and read head RHDm2), and moves read head RHDm1 and read head RHDm2 to positions facing track STRi. Then, the read processing unit 63 controls the driving of the selection circuit 3Sa, causes the selection circuit 3Sa to select head HDm (read head RHDm1 and read head RHDm2), and independently reads the user data of track STRi via the selection circuit 3Sa.

[0096] The processing circuit 4PC can synthesize and process the signal read by the read head RHDm1 and the signal read by the read head RHDm2, and output a synthesized processed signal with reduced noise components.

[0097] The magnetic disk device 1 according to the comparative example configured as described above can read data from one track STRi using two read heads RHDm1 and RHDm2, thereby obtaining high-quality data with reduced noise. The selection circuit 3Sa can connect to only one head HD at a time. Therefore, when detecting defects that may exist on a recording layer L, the selection circuit 3Sa selects one head HD, and the detection unit 65 can detect (inspect) whether a defect exists on one recording layer L. The management unit 66 can manage information about areas of the recording layer L where defects exist.

[0098] However, in order to shorten the time required to detect defects, it is desirable that the selection circuit 3Sa selects two or more heads HD simultaneously and simultaneously detects (inspects) whether or not there are any defects in two or more recording layers L.

[0099] (One embodiment) Next, the configuration of the magnetic disk device 1 according to one embodiment will be described. Fig. 13 is a block diagram showing the configuration of the magnetic disk device 1 according to one embodiment. The magnetic disk device 1 has the same configuration as the magnetic disk device 1 of the comparative example, except for the configuration described in this embodiment.

[0100] 13, the head amplifier IC 130 has a selection circuit 3Sb instead of the selection circuit 3Sa. The R / W channel 140 further has a read channel 14R2 and a selection circuit 14S. The selection circuit 3Sb will be described in detail later, but it is connected to multiple read heads RHD and can select two or more read heads from the multiple read heads RHD.

[0101] The R / W channel 140 includes a read channel 14R1. When the selection circuit 14S selects the read channel 14R1, the magnetic disk device 1 can use the TDMR in the same way as in the comparative example described above, and can process two types of signals simultaneously captured from the same data track (the same data sector) to read data.

[0102] Fig. 14 is a plan view showing the multiple arms 30 and multiple heads HD according to this embodiment. In Fig. 14, attention is focused on two arms 30 and two heads HDm and HDn among the multiple arms 30 and multiple heads HD.

[0103] 14, the heads HDm and HDn are each supported by an arm 30. The actuator (VCM 24) can control the operation of the multiple arms 30, and can move the multiple arms 30 in a uniform manner.

[0104] Here, let us look at the positional relationship between head HDm and head HDn. Head HDm and head HDn overlap in the direction along the rotation axis of the disk DK. However, as in the illustrated example, head HDm and head HDn may not overlap in the direction along the rotation axis of the disk DK. In that case, head HDm and head HDn may be misaligned in the radial direction d1 of the disk DK. Furthermore, head HDm and head HDn may be misaligned in the circumferential direction of the disk DK.

[0105] Figure 15 is a plan view showing a portion of the two recording layers Lm, Ln and the two heads HDm, HDn in this embodiment, and is a diagram for explaining the positional relationship between the two recording layers Lm, Ln and the two heads HDm, HDn in the radial direction d1. As shown in Fig. 15, the multiple recording layers L include a recording layer Lm and a recording layer Ln. In the direction along the rotation axis of the disc DK, the tracks STRi of the recording layer Lm and the tracks STRi of the recording layer Ln overlap. However, as shown in Fig. 15, the tracks STRi of the recording layer Lm and the tracks STRi of the recording layer Ln may be positioned with a deviation in the radial direction d1.

[0106] The plurality of write heads WHD include a write head WHDm that writes data onto the recording layer Lm, and a write head WHDn that writes data onto the recording layer Ln. The write processing unit 62 can select a shingled recording format in which, for example, data from track STR(i+3) is written over data from track STR(i+2) on recording layer Lm in an overwrite direction d5 parallel to the radial direction d1. Furthermore, the write processing unit 62 can select a shingled recording format in which, for example, data from track STR(i) is written over data from track STRi on recording layer Ln in an overwrite direction d6 parallel to the radial direction d1. In the example of FIG. 15, the overwriting direction d5 and the overwriting direction d6 are the same, but they may be opposite to each other.

[0107] The plurality of read heads RHD include a read head RHDm1 and a read head RHDm2 that read data from the recording layer Lm, and a read head RHDn1 and a read head RHDn2 that read data from the recording layer Ln.

[0108] The head HDm has a write head WHDm, a read head RHDm1, and a read head RHDm2, while the head HDn has a write head WHDn, a read head RHDn1, and a read head RHDn2.

[0109] During the period when data is written to track STR(i+3) on recording layer Lm using write head WHDm, a first offset amount which is the distance from write head WHDm to read head RHDm1 in the first direction da is defined as Cm, a second offset amount which is the distance from write head WHDn to read head RHDn2 in the first direction da is defined as Cn, and a third offset amount which is the distance from read head RHDm1 to read head RHDn2 in the first direction da is defined as C(m, n). The first offset amount Cm, the second offset amount Cn, and the third offset amount C(m, n) each depend on the Yaw angle, and may be common to each band BA or each zone Z.

[0110] FIG. 16 is a circuit diagram showing the selection circuit 3Sb of the head amplifier IC 130 according to this embodiment. As shown in Figure 16, the selection circuit 3Sb is a multiplexer that receives many signals and outputs six signals. The selection circuit 3Sb is connected to multiple read heads RHD. The selection circuit 3Sb can freely select two or more read heads RHD from the multiple read heads RHD. Therefore, the heads HD that the selection circuit 3Sb can connect to at one time are two or more heads HD from heads HD1 to HDg. In this example, the selection circuit 3Sb is connected to head HD1 and head HDg.

[0111] Of the terminals of the selection circuit 3Sb on the head HD1 side, the positive terminal R0P and the negative terminal R0N are connected to the read head RHD11 of the head HD1. Of the terminals of the selection circuit 3Sb on the head HDg side, the positive terminal RnP and the negative terminal RnN are connected to the read head RHDg1 of the head HDg. Of the terminals of the selection circuit 3Sb on the head HD1 side, the positive terminal W0P and the negative terminal W0N are connected to the write head WHD1 of the head HD1.

[0112] Of the terminals of the selection circuit 3Sb on the R / W channel 140 side, the positive terminal RDP and the negative terminal RDN are connected to the read amplifier 3R1. The positive terminal RDP2 and the negative terminal RDN2 are connected to the read amplifier 3R2. The positive terminal WDP and the negative terminal WDN are connected to the write driver 3W.

[0113] In this embodiment, the signal extracted from the read head RHD and the signal input to the write head WHD are both differential signals. However, in the following description, the pair of signals extracted from the read head RHD may be collectively referred to as a read signal, and the pair of signals input to the write head WHD may be collectively referred to as a write signal.

[0114] FIG. 17 is a block diagram showing the configuration of a portion of the magnetic disk device 1 according to this embodiment, and shows the configuration of a read channel 14R2 different from the read channel 14R1 shown in FIG. As shown in Figures 17 and 13, when the read target selection unit 64 selects recording layer Lm and recording layer Ln, the read processing unit 63 controls the driving of the selection circuit 3Sb, causing the selection circuit 3Sb to select read heads RHDm1 and RHDn2, and data on recording layer Lm and data on recording layer Ln can be read simultaneously via the selection circuit 3Sb. Here, data on track STRi on recording layer Lm and data on track STR(i-2) on recording layer Ln can be read simultaneously. The detection unit 65 can detect the state of recording layer Lm (track STRi on recording layer Lm) and the state of recording layer Ln (track STR(i-2) on recording layer Ln) based on the signals read by read heads RHDm1 and RHDn2.

[0115] Since the states of the two recording layers L can be detected simultaneously, it is possible to obtain a magnetic disk device 1 that can efficiently detect defects on the disk DK. For example, when applied during the manufacturing of the magnetic disk device 1, the test time required to detect defects can be shortened, thereby shortening the manufacturing time and contributing to reducing manufacturing costs.

[0116] Furthermore, when detecting the states of the two recording layers L simultaneously, the read processing unit 63 controls the driving of the selection circuit 14S to cause the selection circuit 14S to select the read channel 14R2. The read channel 14R2 has multiple processing circuits. In this embodiment, the read channel 14R2 has a first processing circuit 4PC1 and a second processing circuit 4PC2. When the read target selection unit 64 selects the recording layer Lm and the recording layer Ln, the first processing circuit 4PC1 processes the signal read by the read head RHDm1 and outputs a first processed signal in which noise components have been reduced, and the second processing circuit 4PC2 processes the signal read by the read head RHDn2 and outputs a second processed signal in which noise components have been reduced. The detection unit 65 can detect the state of the recording layer Lm and the state of the recording layer Ln based on the first processed signal and the second processed signal.

[0117] The first processing circuit 4PC1 includes an LPF 4R1a, an ADC 4R2a, an FIR filter 4R3a, and a defect detection circuit 4R6a. The LPF4R1a is connected to the read head RHDm1 of the head HDm via the selection circuit 14S and the read amplifier 3R1 and selection circuit 3Sb of the head amplifier IC 130. The LPF4R1a can remove noise contained in the first read signal read by the read head RHDm1 and amplified by the read amplifier 3R1. The ADC4R2a is connected to the LPF4R1a and can convert the first read signal into a digital signal.

[0118] The FIR filter 4R3a is connected to the ADC 4R2a. The FIR filter 4R3a is a one-dimensional FIR filter. The FIR filter 4R3a can perform waveform equalization processing to equalize the waveform of the first read signal so as to minimize the error rate of the first read signal. The FIR filter 4R3a can output first waveform equalization data. The defect detection circuit 4R6a can output, as a first processed signal, information indicating the presence or absence of a defect in the track STRi (data sector) of the recording layer Lm and the range of the defect, based on the data provided by the FIR filter 4R3a.

[0119] The second processing circuit 4PC2 includes an LPF 4R1b, an ADC 4R2b, an FIR filter 4R3b, and a defect detection circuit 4R6b. The LPF4R1b is connected to the read head RHDn2 of the head HDn via the selection circuit 14S and the read amplifier 3R2 and selection circuit 3Sb of the head amplifier IC 130. The LPF4R1b can remove noise contained in the second read signal read by the read head RHDn2 and amplified by the read amplifier 3R2. The ADC4R2b is connected to the LPF4R1b and can convert the second read signal into a digital signal.

[0120] The FIR filter 4R3b is connected to the ADC 4R2b. The FIR filter 4R3b is a one-dimensional FIR filter. The FIR filter 4R3b can perform waveform equalization processing to equalize the waveform of the second read signal so as to minimize the error rate of the second read signal. The FIR filter 4R3b can output second waveform equalization data. The defect detection circuit 4R6b can output information indicating the presence or absence of a defect in track STR(i-2) (data sector) of recording layer Ln and the range of the defect as a second processed signal based on the data provided by the FIR filter 4R3b. This allows the detection unit 65 to simultaneously detect the state of track STRi on recording layer Lm and the state of track STR(i-2) on recording layer Ln based on the first processed signal and the second processed signal.

[0121] When detecting the state of the recording layer L using the read channel 14R2 or the like, the data written to the recording layer L is different from the user data. The data of the recording layer Lm, the data of the recording layer Ln, etc. are bit data in which the arrangement of codes is simpler than that of the user data. For example, the data is one in which the codes are arranged regularly, such as 0, 1, 0, 1, .... By reading such simplified bit data, the state of the recording layer L can be detected, and the read channel 14R2 can be configured simply.

[0122] When the detection unit 65 detects a defect in the recording layer Lm, the management unit 66 manages information about the area of ​​the recording layer Lm where the defect exists, determines one or more sectors SC located in the area where the defect exists as abnormal sectors, and can exclude each abnormal sector from being subject to write processing and read processing.

[0123] For example, when the detection unit 65 or the like detects the state of zone Ze in Fig. 9, the management unit 66 can determine that sectors SC (STRb0,4) and SC (STRb1,4) of band BAb are abnormal sectors, and can treat sectors SC (STRb0,4) and SC (STRb1,4) of band BAb as unused sectors NSC.

[0124] Next, the write processing of the write processing unit 62 will be described. Fig. 18A is a plan view showing a part of one recording layer Lm and one head HDm according to this embodiment, and shows a state in which a write processing is being performed in which one write head WHDm is used to write data to one track STRi on the one recording layer Lm. Fig. 18B is a plan view showing a part of another recording layer Ln and another head HDn according to this embodiment, and shows the positional relationship between the recording layer Ln and the head HDn during the write processing of Fig. 18A.

[0125] 18A and 18B, the read head RHDm1 is opposed to the track STR(i+5), and the write head WHDm is opposed to the track STRi. The write processing unit 62 can write data to the track STRi using the write head WHDm. When data is being written to the track STRi of the recording layer Lm, the positional relationship between the recording layer Ln and the head HDn is examined. The read head RHDn2 faces the track STR(i+3), and the write head WHDn faces the track STRi.

[0126] Fig. 19A is a plan view showing a part of the recording layer Ln and a head HDn according to this embodiment, and shows a state in which a write process is being performed to write data to track STR(i-2) of the recording layer Ln using a write head WHDn. Fig. 19B is a plan view showing a part of the recording layer Lm and a head HDm according to this embodiment, and shows the positional relationship between the Lm recording layer and the head HDm during the write process of Fig. 19A.

[0127] 19A and 19B, by positioning the read head RHDn2 facing the track STR(i+1), the write head WHDn faces the track STR(i-2). The write processing unit 62 can write data to the track STR(i-2) using the write head WHDn. If we look at the positional relationship between the recording layer Lm and the head HDm while data is being written to the track STR(i-2) of the recording layer Ln, the read head RHDm1 faces the track STR(i+3) and the write head WHDm faces the track STR(i-2).

[0128] Next, the read processing of the read processing unit 63 will be described. Fig. 20A is a plan view showing a part of the recording layer Lm and a head HDm according to this embodiment, and shows a state in which a read process is being performed to read data from track STRi on the recording layer Lm using a read head RHDm1. Fig. 20B is a plan view showing a part of the recording layer Ln and a head HDn according to this embodiment, and shows a state in which a read process is being performed to read data from track STR(i-2) on the recording layer Ln using a read head RHDn2 during the read process of Fig. 20A.

[0129] When the read target selection unit 64 selects track STRi on recording layer Lm and track STR(i-2) on recording layer Ln, the read processing unit 63 drives the actuator (VCM24) to control the seek operation of read heads RHDm1 and RHDn2, and moves read head RHDm1 to a position opposite track STRi. As a result, read head RHDn2 moves to a position opposite track STR(i-2).

[0130] Next, the read processing unit 63 controls the driving of the selection circuit 3Sb, causing the selection circuit 3Sb to select the read head RHDm1 and the read head RHDn2, and can simultaneously read the data of the track STRi on the recording layer Lm and the data of the track STR(i-2) on the recording layer Ln via the selection circuit 3Sb.

[0131] The detection unit 65 can detect the state of the track STRi on the recording layer Lm and the state of the track STR(i-2) on the recording layer Ln based on the signal read by the read head RHDm1 and the signal read by the read head RHDn2.

[0132] In order to simultaneously read data from track STRi on recording layer Lm and data from track STR(i-2) on recording layer Ln, it is necessary to write data (simplified bit data) for detecting the state of track STR to these tracks STR in advance, as shown in Figures 18A, 18B, 19A, and 19B.

[0133] Here, the first direction da, which is parallel to the radial direction d1 and extends from the outer periphery to the inner periphery of the disk DK, is defined as positive. During the period when data is written to the track STRi using the write head WHDm, the position of the read head RHDm1 in the radial direction d1 is defined as a reference position, and the first offset amount is defined as Cm, the second offset amount is defined as Cn, and the third offset amount is defined as C(m, n). Then, the offset correction amount calculated from −Cm+Cn+C(m,n) is set to ΔCR.

[0134] Then, when writing data to track STR(i-2) using write head WHDn, the write processing unit 62 simply offsets read head RHDn2 by ΔCR from the reference position in the first direction da and positions write head WHDn opposite track STR(i-2) on recording layer Ln. This makes it possible to write data to track STRi on recording layer Lm and track STR(i-2) on recording layer Ln, which are positioned so that data can be read simultaneously.

[0135] Then, by using the offset correction amount ΔCR, data can be written to the desired radial position (position in the radial direction d1) of each recording layer L. Therefore, in the direction along the rotation axis of the disk DK, the head HDm and the head HDn do not need to overlap, and the track STRi of the recording layer Lm and the track STRi of the recording layer Ln do not need to overlap. For example, the track pitches of the multiple recording layers L do not need to be the same.

[0136] Furthermore, the heads HDm and HDn may be positioned with a circumferential offset on the disk DK, and the servo areas of the recording layers Lm and Ln may be positioned with a circumferential offset on the disk DK. Next, we will focus on the read process that takes into account the circumferential offset of the head HD and the servo areas.

[0137] Figure 21 is a diagram showing the state in which a read process is being performed in this embodiment to simultaneously read data from track STRi on recording layer Lm and data from track STR(i-2) on recording layer Ln, and also shows the read gate RG, and is a diagram for explaining the read process when the timing at which read head RHDn2 reaches the specified read position is later than the timing at which read head RHDm1 reaches the specified read position.

[0138] 21 and 13, the gate generation unit 151 can generate a read gate RG. When the gate detection unit 14D detects that the read gate RG is asserted, it can cause the read processing unit 63 to execute a read process. The read head RHDm1 and the read head RHDn2 move in the moving direction d2 above the track STRi on the recording layer Lm and the track STR(i-2) on the recording layer Ln, respectively.

[0139] The track STRi on the recording layer Lm and the track STR(i-2) on the recording layer Ln each have a plurality of servo areas SV and a plurality of data areas DTR arranged alternately in the circumferential direction. In the track STRi of the recording layer Lm, the multiple servo areas SV include a first servo area SV1 and a second servo area SV2, and the multiple data areas DTR include a first data area DTR1 that follows the first servo area SV1 and precedes the second servo area SV2 in the travel direction d2.

[0140] In track STR(i-2) of recording layer Ln, the multiple servo areas SV include a third servo area SV3 and a fourth servo area SV4, and the multiple data areas DTR include a second data area DTR2 that follows the third servo area SV3 and precedes the fourth servo area SV4 in the travel direction d2.

[0141] Of the multiple servo areas SV in the track STR(i-2) of the recording layer Ln, the third servo area SV3 is the servo area that the read head RHDn2 comes closest to when the read head RHDm1 faces the first servo area SV1. Of the multiple servo areas SV in the track STR(i-2) of the recording layer Ln, the fourth servo area SV4 is the servo area that the read head RHDn2 comes closest to when the read head RHDm1 faces the second servo area SV2.

[0142] Here, the timing when the read head RHDm1 passes the rear end position of the first servo area SV1 of the track STRi on the recording layer Lm is defined as the first timing T1. The timing when the read head RHDn2 passes the rear end position of the third servo area SV3 of the track STR(i-2) on the recording layer Ln is defined as the second timing T2. The correction period, which is the time period between the first timing T1 and the second timing T2, is defined as ΔTR.

[0143] 21 shows a case where the second timing T2 is later than the first timing T1. In this case, the gate generating unit 151 asserts the read gate RG at the first timing T1, maintains the read gate RG in the asserted state at the third timing T3 when the read head RHDm1 passes the beginning of the second servo region SV2 of the track STRi on the recording layer Lm, and negates the read gate RG at the fourth timing T4, which is ΔTR after the third timing T3. This makes it possible to read all the data in the first data area DTR1 and all the data in the second data area DTR2.

[0144] 22 is a diagram showing a state in which a read process is being performed in which data on track STRi of recording layer Lm and data on track STR(i-2) of recording layer Ln are simultaneously read in this embodiment, and also shows a read gate RG, and is a diagram for explaining the read process when the timing at which read head RHDn2 reaches a predetermined read position coincides with the timing at which read head RHDm1 reaches the predetermined read position. FIG. 22 shows a case in which second timing T2 coincides with first timing T1.

[0145] As shown in FIGS. 22 and 13, the gate generation unit 151 asserts the read gate RG at a first timing T1, and negates the read gate RG at a third timing T3. This makes it possible to read all the data in the first data area DTR1 and all the data in the second data area DTR2.

[0146] 23 is a diagram showing a state in which a read process is being performed in which data from track STRi on recording layer Lm and data from track STR(i-2) on recording layer Ln are simultaneously read in this embodiment, and also shows a read gate RG, and is a diagram for explaining the read process when the timing at which read head RHDn2 reaches a predetermined read position is earlier than the timing at which read head RHDm1 reaches the predetermined read position. FIG. 23 shows a case in which the second timing T2 is earlier than the first timing T1.

[0147] As shown in Figures 23 and 13, the gate generation unit 151 asserts the read gate RG at the fifth timing T5, which is ΔTR before the first timing T1, maintains the read gate RG in the asserted state at the first timing T1, and switches the read gate RG to negate at the third timing T3. This makes it possible to read all the data in the first data area DTR1 and all the data in the second data area DTR2. In any of the cases shown in FIGS. 21 to 23, the data in the first data area DTR1 and the data in the second data area DTR2 can be read without any omission.

[0148] Next, the management of defects on the recording layer L by the management unit 66 will be described. Fig. 24 is a plan view showing a part of the recording layer Lm according to this embodiment, showing a state in which a defect DE detected on the recording layer Lm straddles six adjacent sectors SC. Fig. 25 is a plan view showing a part of the recording layer Lm according to this embodiment, showing the state after the track width Wt and sector length Ls of the recording layer Lm have been changed, following Fig. 24, showing a state in which the defect DE straddles two adjacent sectors SC.

[0149] 24 and 13, the width of each track STR in the radial direction d1 is defined as the track width Wti, and the length of each data sector STR in the circumferential direction is defined as the sector length Lsi. When the detection unit 65 detects a defect DE existing in the recording layer Lm, the management unit 66 can manage information about the area where the defect DE exists in a reference width unit with a higher resolution than the track width Wti in the radial direction d1, and in a reference length unit with a higher resolution than the sector length Lsi in the circumferential direction.

[0150] Here, consider a case where the track width Wt and sector length Ls are changed during the period in which the user is using the magnetic disk device 1.

[0151] 25 and 13, the track width Wti is changed to the track width Wth, and the sector length Lsi is changed to the sector length Lsh. In this case, the management unit 66 determines that the sector SC(h+1) of the track STRj on the recording layer Lm and the sector SC(h+1) of the track STR(j+1) are abnormal sectors, and can treat them as unused sectors NSC.

[0152] 24 before the track width Wt and sector length Ls were changed, it can be seen that the number of unused sectors NSC has decreased from 6 to 2. As such, since it is possible to reduce the number of unused sectors NSC in some cases, it is preferable to manage the track width Wt in units of reference widths with higher resolution and manage the sector lengths Ls in units of reference lengths with higher resolution.

[0153] According to the magnetic disk device 1 of the above embodiment configured as described above, the magnetic disk device 1 is equipped with a plurality of recording layers L, a plurality of write heads WHD, a plurality of read heads RHD, a selection circuit 3Sb, a read target selection unit 64, a read processing unit 63, and a detection unit 65.

[0154] The multiple recording layers L are provided on the same or different disks DK, and each includes a recording layer Lm and a recording layer Ln. The multiple write heads WHD include a write head WHDm that writes data to the recording layer Lm and a write head WHDn that writes data to the recording layer Ln. The multiple read heads RHD include a read head RHDm1 that reads data from the recording layer Lm and a read head RHDn2 that reads data from the recording layer Ln.

[0155] The selection circuit 3Sb is connected to the plurality of read heads RHD and can select two or more read heads from the plurality of read heads RHD. The read processing unit 63 can execute a read process to read data from each recording layer L.

[0156] When the read target selection unit 64 selects the recording layer Lm and the recording layer Ln, the read processing unit 63 controls the driving of the selection circuit 3Sb, causing the selection circuit 3Sb to select the read head RHDm1 and the read head RHDn2, so that the data on the recording layer Lm and the data on the recording layer Ln can be read simultaneously via the selection circuit 3Sb. The detection unit 65 can detect the states of the recording layer Lm and the recording layer Ln based on the signals read by the read head RHDm1 and the read head RHDn2. Since data on the two recording layers L can be read simultaneously, it is possible to obtain a magnetic disk device 1 that can efficiently detect defects on the disk DK.

[0157] Although the embodiments of the present invention have been described, the above embodiments are presented as examples and are not intended to limit the scope of the invention. The above novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the inventions and their equivalents as defined in the claims.

[0158] For example, the selection circuit 3Sb may be configured to select three or more read heads RHD from the plurality of read heads RHD. In this case, the head amplifier IC 130 may have three or more read amplifiers 3R, including a read amplifier 3R1 and a read amplifier 3R2. The read channel 14R2 may have three or more processing circuits 4PC, including a first processing circuit 4PC1 and a second processing circuit 4PC2. This allows data from three or more recording layers L to be read simultaneously, making it possible to more efficiently detect defects on the disk DK.

[0159] The above-described technique is not limited to hybrid recording type magnetic disk devices, but may also be applied to shingled recording type magnetic disk devices and normal recording type magnetic disk devices. [Explanation of symbols]

[0160] 1...magnetic disk device, 60...MPU, 61...read / write processing unit, 62...write processing unit, 63...read processing unit, 64...read target selection unit, 65...detection unit, 66...management unit, 70...volatile memory, 80...buffer memory, 90...non-volatile memory, 100...host, 110...system controller, 120...driver IC, 130...head amplifier IC, 3Sb...selection circuit, 3R...read amplifier, 3W...write driver, 140...R / W channel, 14S...selection circuit, 14D...gate detection unit, 14R1...read channel, 4PC...processing circuit, 14R2...read channel, 4PC1...first processing circuit, 4PC2...second processing circuit path, 150...HDC, 151...gate generation unit, 24...VCM, 30...arm, DK...disk, L...recording layer, DTR...data area, SV...servo area, STR...track, SC...sector, NSC...unused sector, HD...head, WHD...write head, RHD...read head, DE...defect, Ls...sector length, Wt...track width, RG...read gate, Cm...first offset amount, Cn...second offset amount, C(m,n)...third offset amount, ΔCR...offset correction amount, T1, T2, T3, T4, T5...timing, d1...radial direction, d2...traveling direction, d3...rotational direction, d5, d6...overwrite direction, da...first direction.

Claims

1. a plurality of recording layers provided on the same or different discs, the plurality of recording layers including a first recording layer and a second recording layer; a plurality of write heads, the plurality of write heads including a first write head that writes data onto the first recording layer and a second write head that writes data onto the second recording layer; a plurality of read heads, the plurality of read heads including a first read head for reading data from the first recording layer and a second read head for reading data from the second recording layer; a selection circuit connected to the plurality of read heads and capable of selecting two or more read heads from the plurality of read heads; a read target selection unit; a read processing unit capable of executing a read process for reading data from each of the recording layers; a detection unit, When the read target selection unit selects the first recording layer and the second recording layer, the read processing unit controls driving of the selection circuit, causes the selection circuit to select the first read head and the second read head, and simultaneously reads the data of the first recording layer and the data of the second recording layer via the selection circuit; the detection unit detects a state of the first recording layer and a state of the second recording layer based on a signal read by the first read head and a signal read by the second read head. Magnetic disk device.

2. the data of the first recording layer and the data of the second recording layer are bit data whose code arrangement is simpler than that of user data; 2. The magnetic disk drive according to claim 1.

3. It further comprises an administrative department, Each of the recording layers has a plurality of data tracks aligned in the radial direction of the disk, Each of the data tracks has a plurality of data sectors arranged in the circumferential direction of the disk, When the detection unit detects a defect present in the first recording layer, the management unit manages information about the area of ​​the first recording layer where the defect exists, determines one or more data sectors located in the area where the defect exists as abnormal sectors, and excludes each of the abnormal sectors from the targets of the write process for writing data and the read process.

2. The magnetic disk drive according to claim 1.

4. a first read channel having a plurality of processing circuits connected to the selection circuit, the plurality of processing circuits including a first processing circuit and a second processing circuit; When the read target selection unit selects the first recording layer and the second recording layer, the first processing circuit processes the signal read by the first read head and outputs a first processed signal in which noise components have been reduced; the second processing circuit processes the signal read by the second read head and outputs a second processed signal in which noise components have been reduced; the detection unit detects a state of the first recording layer and a state of the second recording layer based on the first processed signal and the second processed signal.

2. The magnetic disk drive according to claim 1.

5. a plurality of arms having a first arm; an actuator for moving the plurality of arms; a second read channel connected to the selection circuit and having a processing circuit for two-dimensional magnetic recording technology; a write processing unit capable of executing a write process for writing data to each of the recording layers, the plurality of read heads further include a third read head that is supported by the first arm together with the first read head and that reads data from the first recording layer; the first recording layer has a first data track; the write processing unit writes user data to the first data track using the first write head; When the read target selection unit selects the first data track of the first recording layer, The read processing unit driving the actuator to control a seek operation of the first read head and the third read head, and moving the first read head and the third read head to a position facing the first data track; controlling the driving of the selection circuit, causing the selection circuit to select the first read head and the third read head, and independently reading the user data of the first data track via the selection circuit; the processing circuit synthesizes and processes the signal read by the first read head and the signal read by the third read head, and outputs a synthesized processed signal in which noise components have been reduced.

2. The magnetic disk drive according to claim 1.

6. a plurality of arms including a first arm and a second arm; an actuator that moves the plurality of arms uniformly; a write processing unit capable of executing a write process for writing data to each of the recording layers, the first arm supports the first write head and the first read head; the second arm supports the second write head and the second read head; the first recording layer has a first data track; the second recording layer has a second data track; the write processing unit writes data to the first data track using the first write head and writes data to the second data track using the second write head; When the read target selection unit selects the first data track of the first recording layer and the second data track of the second recording layer, The read processing unit driving the actuator to control a seek operation of the first read head and the second read head, moving the first read head to a position facing the first data track, and moving the second read head to a position facing the second data track; controlling the driving of the selection circuit, causing the selection circuit to select the first read head and the second read head, and simultaneously reading the data of the first data track and the data of the second data track via the selection circuit; the detection unit detects a state of the first data track and a state of the second data track based on a signal read by the first read head and a signal read by the second read head; If a first direction parallel to the radial direction of the disk, which is from the outer periphery side to the inner periphery side of the disk, is defined as positive, then: During a period in which the data is written to the first data track using the first write head, a position of the first read head in the radial direction of the disk is set as a reference position; a first offset amount that is a distance from the first write head to the first read head in the first direction is defined as Cm; a second offset amount that is a distance from the second write head to the second read head in the first direction is defined as Cn; a third offset amount that is the distance from the first read head to the second read head in the first direction is defined as C(m, n); When the offset correction amount calculated from −Cm+Cn+C(m, n) is ΔCR, When writing the data to the second data track using the second write head, the write processing unit offsets the second read head from the reference position by ΔCR in the first direction and causes the second write head to face the second data track; 2. The magnetic disk drive according to claim 1.

7. a gate generator for generating a read gate; a gate detection unit that causes the read processing unit to execute a read process when it detects that the read gate is asserted; the first read head and the second read head move above the first data track and the second data track, respectively, in a moving direction along the circumferential direction of the disk; each of the first data track and the second data track has a plurality of servo areas and a plurality of data areas arranged alternately in the circumferential direction; In the first data track, the plurality of servo areas include a first servo area and a second servo area, and the plurality of data areas include a first data area that follows the first servo area and is located before the second servo area in the traveling direction, In the second data track, the plurality of servo areas include a third servo area and a fourth servo area, and the plurality of data areas include a second data area that follows the third servo area and is located before the fourth servo area in the traveling direction, the third servo area of ​​the plurality of servo areas of the second data track is the servo area to which the second read head is closest when the first read head faces the first servo area, a timing when the first read head passes the rear end position of the first servo area of ​​the first data track is defined as a first timing; a timing when the second read head passes the rear end position of the third servo area of ​​the second data track is defined as a second timing; When a correction period, which is the time period between the first timing and the second timing, is ΔTR, If the second timing is later than the first timing, the gate generation unit asserts the read gate at the first timing, maintains the read gate in an asserted state at a third timing when the first read head passes a leading position of the second servo area of ​​the first data track, and negates the read gate at a fourth timing when ΔTR has elapsed since the third timing; When the second timing coincides with the first timing, the gate generation unit asserts the read gate at the first timing and negates the read gate at the third timing; When the second timing is earlier than the first timing, the gate generation unit asserts the read gate at a fifth timing that is ΔTR earlier than the first timing, maintains the read gate in an asserted state at the first timing, and switches the read gate to a negated state at the third timing.

7. The magnetic disk drive according to claim 6.

8. It further comprises an administrative department, Each of the recording layers has a plurality of data tracks aligned in the radial direction of the disk, Each of the data tracks has a plurality of data sectors arranged in the circumferential direction of the disk, the width of each of the data tracks in the radial direction is defined as a track width; If the length of each data sector in the circumferential direction is defined as a sector length, then: When the detection unit detects a defect present in the first recording layer, the management unit manages information about the defect-containing area in units of a reference width having a higher resolution than the track width in the radial direction, and in units of a reference length having a higher resolution than the sector length in the circumferential direction.

2. The magnetic disk drive according to claim 1.

9. a write processing unit capable of executing a write process for writing data to each of the recording layers, Each of the recording layers has a plurality of data tracks aligned in the radial direction of the disk, The write processing unit a shingled recording format can be selected in which data of a third data track is written over data of a first data track of the first recording layer in a first overwrite direction parallel to the radial direction; and a shingled recording format can be selected in which data of a fourth data track is written overlapping data of a second data track of the second recording layer in a second overwrite direction parallel to the radial direction; 2. The magnetic disk drive according to claim 1.

Images