Methods for setting disk devices and refresh thresholds

Abstract

This invention provides a disk device capable of improving performance and data reliability, and a method for setting refresh thresholds. The disk device of this embodiment includes: a disk having a first track; a head having a heater for writing data to the disk and reading data from the disk; and a controller for setting variations in parameters associated with write processing to the disk within one cycle of the first track, such that variations in evaluation metrics corresponding to write / read processing characteristics are suppressed within one cycle of the first track.

Description

[0001] This application enjoys priority based on Japanese Patent Application No. 2021-142613 (filed on September 1, 2021). This application incorporates the entire contents of the basic application by reference to that basic application. Technical Field

[0002] The embodiments of the present invention relate to a disk device and a method for setting a refresh threshold. Background Technology

[0003] With the increasing recording density of disk drives (hereinafter referred to as disks), the variation in the recording reproduction characteristics of a disk within one week due to non-uniformity of the magnetic film or mechanical characteristics has become more apparent as a metric for evaluation, such as bit error rate (BER). Ideally, the BER should be constant within a predetermined track on the disk.

[0004] Furthermore, in disk devices, when data is written, side erase may occur due to the influence of leakage flux from the head (Adjacent Track Interference: ATI). To prevent side erase, disk devices have a process (flush processing or rewrite processing) that rewrites the data on a predetermined track if data has been written to adjacent tracks of a predetermined track more than a predetermined number of times. Summary of the Invention

[0005] The problem to be solved by the embodiments of the present invention is to provide a disk device that can improve performance and data reliability and a method for setting refresh threshold.

[0006] The disk device according to this embodiment includes: a disk having a first track; a head having a heater for writing data to the disk and reading data from the disk; and a controller for setting the variation of parameters associated with write processing to the disk within one week of the first track, so as to suppress the variation of evaluation indicators corresponding to write / read processing characteristics within one week of the first track. Attached Figure Description

[0007] Figure 1 This is a block diagram illustrating the configuration of a disk device according to an embodiment.

[0008] Figure 2 This is a schematic diagram illustrating an example of a disk in an embodiment.

[0009] Figure 3 This is an enlarged sectional view showing an example of the disc and head.

[0010] Figure 4 This is a schematic diagram illustrating an example of write processing.

[0011] Figure 5 This is a schematic diagram illustrating an example of the variation of measured evaluation indicators, approximate evaluation indicators, and modified evaluation indicators for a predetermined magnetic track at a circumferential position.

[0012] Figure 6 This is a schematic diagram illustrating an example of the variation of the evaluation index for the correction of the circumferential position and the variation of the correction writing parameters in this embodiment.

[0013] Figure 7 This is a schematic diagram illustrating an example of the variation in BER (Bit Rate) of a predetermined track for a circumferential position when a fringe write is performed.

[0014] Figure 8 This is a schematic diagram illustrating an example of the variation of the TBG value of a predetermined track at a circumferential position and the variation of the threshold correction value at the circumferential position in an embodiment.

[0015] Figure 9 This is a schematic diagram illustrating an example of the variation of the segmentation threshold of the predetermined track for the segmented region in an embodiment.

[0016] Figure 10 This is a schematic diagram illustrating an example of the division of a predetermined magnetic track.

[0017] Figure 11 This is a schematic diagram illustrating an example of a table TB showing the number of writes and the threshold for dividing the region in an implementation method.

[0018] Figure 12 This is a flowchart illustrating an example of a method for setting a refresh threshold in an implementation.

[0019] Figure 13 This is a schematic diagram illustrating an example of a refresh processing method according to an implementation method.

[0020] [Label Explanation]

[0021] 1…Disk device, 10…Disk, 10a…User data area, 10b…System area, 12…Spindle motor (SPM), 13…Arm, 14…Voice coil motor (VCM), 15…Head, 15W…Write head, 15R…Read head, 20…Driver IC, 30…Head amplifier IC, 40…Read / write (R / W) channel, 50…Hard disk controller (HDC), 60…Microprocessor (MPU), 70…Volatile memory, 80…Non-volatile memory, 90…Buffer memory, 100…Host system (host), 130…System controller. Detailed Implementation

[0022] The embodiments will now be described with reference to the accompanying drawings. Furthermore, the drawings are merely examples and do not limit the scope of the invention.

[0023] (Implementation Method)

[0024] Figure 1 This is a block diagram showing the configuration of the disk device 1 according to an embodiment.

[0025] The disk drive 1 includes a head disk assembly (HDA), a driver IC 20, a head amplifier integrated circuit (hereinafter referred to as head amplifier IC or preamplifier) ​​30, volatile memory 70, non-volatile memory 80, buffer memory (cache) 90, and a system controller 130 as a single-chip integrated circuit. Furthermore, the disk drive 1 is connected to a host system (hereinafter referred to as host) 100.

[0026] The HDA includes a disk (hereinafter referred to as a disk) 10, a spindle motor (hereinafter referred to as a SPM) 12, an arm 13 with a head 15 mounted thereon, and a voice coil motor (hereinafter referred to as a VCM) 14. The disk 10 is mounted on the SPM 12 and rotates by the drive of the SPM 12. The arm 13 and VCM 14 constitute an actuator. The actuator, driven by the VCM 14, moves the head 15 mounted on the arm 13 to a predetermined position on the disk 10. Two or more disks 10 and heads 15 can also be provided.

[0027] Disk 10 allocates a user data area 10a for use by the user and a system area 10b for writing information required for system management to its writable data area. Hereinafter, the direction from the inner periphery to the outer periphery of disk 10 or the direction from the outer periphery to the inner periphery of disk 10 will be referred to as the radial direction. Within the radial direction, the direction from the inner periphery to the outer periphery will be referred to as the outer direction (or outer side), and the direction from the inner periphery to the outer periphery will be referred to as the inner direction (or inner side). The circumferential direction corresponds to the direction along the circumference of disk 10. The radial direction and the circumferential direction are orthogonal to each other. Alternatively, a predetermined position in the radial direction of disk 10 may be referred to as the radial position, and a predetermined position in the circumferential direction of disk 10 may be referred to as the circumferential position. Alternatively, the radial position and the circumferential position may be collectively referred to simply as the position. The user data area 10a of disk 10 can be divided into multiple zones. For example, the user data area 10a can be divided in the radial direction into zones (hereinafter, also referred to as zones) containing a predetermined number of tracks. Partitions can be made radially along each track.

[0028] Furthermore, a "track" includes one of several recording areas divided into multiple recording areas in the radial direction of disk 10, a recording area covering one circumference of a predetermined radius position of disk 10, a predetermined recording area at a predetermined radius position of disk 10, a recording area extending in the circumferential direction of disk 10, a recording area corresponding to the path of the head 15 located at the predetermined radius position of disk 10, the path of the head 15 located at the predetermined radius position of disk 10, data written to one of the multiple recording areas divided into multiple recording areas in the radial direction of disk 10, and data written to one circumference of the predetermined radius position of disk 10. The terms "data in the recording area," "data in the predetermined recording area written to a predetermined radius position of disk 10," "data in the recording area written to disk 10 extending in the circumferential direction," "data in the recording area corresponding to the path of the head 15 located at the predetermined radius position of disk 10," "data written along the path of the head 15 located at the predetermined radius position of disk 10," "data extending in the circumferential direction in disk 10," "data written to a predetermined track of disk 10," "data of one circumference of a predetermined track of disk 10," "a portion of the data written to a predetermined track of disk 10," and various other meanings are used. The term "sector" can refer to one of several recording regions divided circumferentially from a predetermined track of disk 10; one of several recording regions divided circumferentially from a predetermined radius position of disk 10; a predetermined recording region of a predetermined track of disk 10; a predetermined circumferential position of a predetermined track of disk 10; a predetermined circumferential position (predetermined location) at a predetermined radius position of disk 10; data written to one of several recording regions divided circumferentially from a predetermined track of disk 10; data written to one of several recording regions divided circumferentially from a predetermined radius position of disk 10; data written to a predetermined recording region of a predetermined track of disk 10; data written to a predetermined circumferential position of a predetermined track of disk 10; data written to a predetermined circumferential position (predetermined location) at a predetermined radius position of disk 10; data written to a predetermined sector; and various other meanings. There are also instances where the "width in the radial direction of the track" is referred to as "track width." There are also cases where the "path that passes through the center position of the predetermined track width" is referred to as the "track center". There are also cases where data that can be used by the user and written to the user data area 10a is referred to as user data.

[0029] The head 15 uses the slider 150 (described later) as its main body and includes a write head 15W and a read head 15R mounted on the slider 150. The write head 15W writes data to the disk 10. The read head 15R reads the data recorded on the disk 10. Furthermore, there are cases where "write head 15W" is simply referred to as "head 15," "read head 15R" is simply referred to as "head 15," and "write head 15W and read head 15R" are collectively referred to as "head 15." There are also cases where the "center portion of head 15" is referred to as "head 15," the "center portion of write head 15W" is referred to as "write head 15W," and the "center portion of read head 15R" is referred to as "read head 15R." There are cases where the "center portion of write head 15W" is simply referred to as "head 15," and the "center portion of read head 15R" is simply referred to as "head 15." There are also cases where "positioning the center of the head 15 in the center of the predetermined magnetic track" is expressed as "positioning the head 15 in the predetermined magnetic track", "arranging the head 15 in the predetermined magnetic track", or "making the head 15 located in the predetermined magnetic track".

[0030] Figure 2 This is a schematic diagram illustrating an example of the disk 10 in an embodiment. For example... Figure 2 As shown, the direction in which disk 10 rotates in the circumferential direction is called the direction of rotation. Furthermore, in... Figure 2 In the example shown, the direction of rotation is counterclockwise, but it can also be the opposite (clockwise). Figure 2 In the middle, disk 10 is divided into an inner peripheral region IR located in the inward direction, an outer peripheral region OR located in the outward direction, and a middle peripheral region MR located between the inner peripheral region IR and the outer peripheral region OR.

[0031] exist Figure 2 In the example shown, disk 10 includes a user data area 10a and a system area 10b. Figure 2 In this configuration, user data area 10a and system area 10b are adjacent in the radial direction. Here, "adjacent" includes not only contacting data, objects, areas, and spaces, but also arrangements separated by a predetermined interval. Figure 2 In this configuration, system area 10b is adjacent to user data area 10a in the outer direction. Alternatively, system area 10b may be adjacent to user data area 10a in the inner direction. Furthermore, system area 10b may be arranged radially between user data areas 10a.

[0032] exist Figure 2 In the example shown, user data area 10a is configured from the inner peripheral area IR to the outer peripheral area OR. System area 10b is configured in the outer peripheral area OR. Alternatively, system area 10b can also be configured in the inner peripheral area IR or the middle peripheral area MR. System area 10b can also be distributed across the outer peripheral area OR, the middle peripheral area MR, or the inner peripheral area IR.

[0033] like Figure 2 As shown, the head 15 is rotated about the rotation axis relative to the disk 10 by the drive of the VCM14 and moved from the inside to the outside to be positioned in a predetermined position, or moved from the outside to the inside to be positioned in a predetermined position.

[0034] Figure 3 This is an enlarged sectional view showing an example of disk 10 and head 15. Hereinafter, the direction from head 15 to disk 10 will be referred to as the downward direction (or lower), and the direction from disk 10 to head 15 will be referred to as the upward direction (or upper). Figure 3 In the middle, the rotation direction B of disk 10 is consistent with the direction of airflow C.

[0035] exist Figure 3 In the example shown, the disk 10 has a substrate 111, a soft magnetic layer 112, a magnetic recording layer 113, and a protective film layer 114 stacked sequentially. The substrate 111 is formed of a non-magnetic material in the shape of a disc. The soft magnetic layer 112 is formed on the substrate 111 from a material exhibiting soft magnetic properties. The magnetic recording layer 113 is formed on the soft magnetic layer 112 and has magnetic anisotropy in a direction perpendicular to the surface of the disk 10. The protective film layer 114 is formed on the magnetic recording layer 113.

[0036] exist Figure 3 In the example shown, head 15 has a slider 150. Slider 150 is formed, for example, from a sintered body of alumina and titanium carbide. Slider 150 has a disk-facing surface (air-supported surface (ABS)) 151 opposite to the surface of disk 10 and a trailing end 153 located on the outflow side of airflow C. Slider 150 includes a write head 15W, a read head 15R, a heater 191, and a heater 192. A portion of the read head 15R and the write head 15W protrudes to the disk-facing surface 151. Heater 191 is disposed between the write head 15W and the read head 15R. Heater 192 is disposed on the opposite side of the read head 15R from the write head 15W. In other words, the read head 15R is disposed between heaters 191 and 192.

[0037] The read head 15R is composed of a magnetic film 161, a shielding film 162, and a shielding film 163. The magnetic film 161 is located between the shielding films 162 and 163, generating a magnetoresistive effect. The shielding film 162 is located on the trailing end 153 side relative to the magnetic film 161. The shielding film 163 is opposite to the shielding film 162. The lower ends of the magnetic film 161, shielding film 162, and shielding film 163 protrude onto the disk-facing surface 151.

[0038] The write head 15W is positioned relative to the read head 15R on the trailing end 153 side of the slider 150. The write head 15W includes a main magnetic pole 171, a trailing shield (write shield) 172, and a recording coil 180 configured to be wound around a magnetic circuit including the main magnetic pole 171 and the write shield 172 in order to allow magnetic flux to flow to the main magnetic pole 171.

[0039] The main magnetic pole 171 is formed of a soft magnetic material with a high saturation magnetic flux density. The main magnetic pole 171 generates a recording magnetic field perpendicular to the surface of the disk 10 in order to magnetize the magnetic recording layer 113 of the disk 10. Figure 3 In the example shown, the main magnetic pole 171 extends almost perpendicularly to the disk-facing surface 151. The lower surface of the front end portion 171a of the main magnetic pole 171 on the disk-facing surface 151 side is exposed to the disk-facing surface 151. The front end portion 171a of the main magnetic pole 171 tapers towards the disk-facing surface 151, forming a narrow columnar shape relative to the other parts. The width of the front end portion 171a of the main magnetic pole 171 in the cross-track direction almost corresponds to the track width. The cross-track direction is, for example, a direction along the radial direction.

[0040] The write shield 172 is formed of a soft magnetic material with a high saturation magnetic flux density. The write shield 172 is provided to effectively enclose the magnetic circuit via the soft magnetic layer 112 directly below the main magnetic pole 171. The write shield 172 is located on the follower end 153 side relative to the main magnetic pole 171. The write shield 172 is connected to the main magnetic pole 171 via an insulator 173. The main magnetic pole 171 and the write shield 172 are electrically insulated and form a magnetic circuit. The write shield 172 is formed in a generally L-shape, having a front end 172a opposite the front end 171a of the main magnetic pole 171 across the write gap. The lower surface of the front end 172a is exposed to the ABS 151 of the slider 150.

[0041] The recording coil 180 is configured to be wound around a magnetic circuit including the main magnetic pole 171 and the write shield 172 in order to direct magnetic flux to the main magnetic pole 171. The recording coil 180 is, for example, positioned between the main magnetic pole 171 and the write shield 172. By supplying a predetermined current (also referred to as recording current (Iw) or writing current (Iw)) to the recording coil 180, a recording magnetic field is generated in the main magnetic pole 171 and the write shield 172. Consequently, the main magnetic pole 171 and the write shield 172 are magnetized. By utilizing the magnetic flux flowing through the magnetized main magnetic pole 171 and the write shield 172, the magnetization direction of the recording bits of the magnetic recording layer 113 of the disk 10 is changed, and a magnetization pattern corresponding to the recording current is recorded on the disk 10.

[0042] The driver IC20 controls the driving of SPM12 and VCM14 according to the control of the system controller 130 (more specifically, MPU60, described later).

[0043] The preamplifier IC 30 includes a read amplifier, a write driver such as a recording current control unit 310, and a heater control unit 320. The read amplifier amplifies the read signal read from the disk 10 and outputs it to the system controller 130 (specifically, the read / write (R / W) channel 40 described later). The recording current control unit 310 is electrically connected to the write head 15W and supplies the recording current corresponding to the write data output from the R / W channel 40 to the write head 15W. In one example, the recording current control unit 310 is electrically connected to the recording coil 180 and supplies the recording current corresponding to the write data output from the R / W channel 40 to the recording coil 180. The recording current control unit 310 supplies the recording current to the write head 15W according to the control of the system controller 130, such as the MPU 60. For example, the recording current control unit 310 supplies the recording current to the recording coil 180 according to the control of the MPU 60. The heater control unit 320 is electrically connected to heaters 191 and 192, and supplies the current output from the R / W channel 40 to drive the heaters to heaters 191 and 192. The heater control unit 320 supplies current to heaters 191 and 192 according to the control of the system controller 130, such as the MPU 60. When the heater control unit 320 supplies current to heaters 191 and 192, heaters 191 and 192 heat up, heating portions of the slider 150 surrounding heaters 191 and 192. As a result, the slider 150, the write head 15W, and the read head 15R thermally expand, and the ABS 151 protrudes towards the surface of the disk 10. Thus, the levitation amount of the head 15 (the distance between the ABS 151 and the surface of the disk 10) can be adjusted by the heaters 191 and 192. The expansion of the slider 150, the write head 15W, and the read head 15R is adjusted according to the value of the current (or voltage) supplied to heaters 191 and 192. That is, the buoyancy of head 15 is adjusted according to the value of the current (or voltage) supplied to heaters 191 and 192.

[0044] Volatile memory 70 is a semiconductor memory whose stored data is lost when the power supply is cut off. Volatile memory 70 stores data required for processing in various parts of disk drive 1. Volatile memory 70 is, for example, DRAM (Dynamic Random Access Memory) or SDRAM (Synchronous Dynamic Random Access Memory).

[0045] Non-volatile memory 80 is a semiconductor memory that records stored data even when the power supply is cut off. Non-volatile memory 80 is, for example, a NOR or NAND type flash ROM (Flash Read Only Memory).

[0046] The buffer memory 90 is a semiconductor memory that temporarily records data transmitted and received between the disk drive 1 and the host computer 100. Furthermore, the buffer memory 90 may be integrated with the volatile memory 70. The buffer memory 90 may be, for example, DRAM, SRAM (Static Random Access Memory), SDRAM, FeRAM (Ferroelectric Random Access Memory), or MRAM (Magnetoresistive Random Access Memory).

[0047] The system controller (controller) 130 is implemented, for example, using a large-scale integrated circuit (LSI) called a System-on-a-Chip (SoC), which integrates multiple components onto a single chip. The system controller 130 includes a read / write (R / W) channel 40, a hard disk controller (HDC) 50, and a microprocessor (MPU) 60. The system controller 130 is electrically connected, for example, to a driver IC 20, a head amplifier IC 30, volatile memory 70, non-volatile memory 80, a buffer memory 90, and a host 100.

[0048] R / W channel 40 performs signal processing for read data transmitted from disk 10 to host 100 and write data transmitted from host 100, according to instructions from MPU 60 (described later). R / W channel 40 has circuitry or functions for measuring the signal quality of read data. R / W channel 40 is electrically connected, for example, to head amplifier IC 30, HDC 50, and MPU 60.

[0049] HDC50 controls the transmission of control data. For example, HDC50 controls the data transmission between host 100 and R / W channel 40 according to instructions from MPU60 (described later). HDC50 is electrically connected, for example, to R / W channel 40, MPU60, volatile memory 70, non-volatile memory 80, and buffer memory 90.

[0050] MPU60 is the main controller that controls the various parts of disk drive 1. MPU60 performs servo control to position the head 15 via VCM14 controlled by driver IC20. MPU60 controls SPM12 via driver IC20 to rotate disk 10. MPU60 controls data writing to disk 10 and selects the destination for data transferred from host 100, such as write data. MPU60 controls data reading from disk 10 and controls the processing of data transferred from disk 10 to host 100, such as read data. Additionally, MPU60 manages the areas where data is recorded. MPU60 is connected to various parts of disk drive 1. MPU60 is electrically connected, for example, to driver IC20, R / W channel 40, and HDC50.

[0051] The MPU60 includes a read / write control unit 610, an access processing control unit 620, and a refresh control unit 630. The MPU60 executes the processing of each component, such as the read / write control unit 610, the access processing control unit 620, and the refresh control unit 630, on the firmware. Alternatively, the MPU60 may also include each component, such as the read / write control unit 610, the access processing control unit 620, and the refresh control unit 630, as circuitry. The read / write control unit 610, the access processing control unit 620, and the refresh control unit 630 may also be included in the R / W channel 40 or the HDC50.

[0052] The read / write control unit 610 controls the read processing of data read from the slave disk 10 and the write processing of data written to the disk 10 according to commands from the host 100. The read / write control unit 610 controls the VCM 14 via the driver IC 20 to position the head 15 at a predetermined position on the disk 10 and perform read or write processing. Hereinafter, the term "access" may be used to mean recording or writing data (or writing) to a predetermined area, reading data (or reading) from a predetermined area, or moving the head 15 to a predetermined area.

[0053] The read / write control unit 610, upon receiving commands from the host 100, performs normal recording by writing data to a predetermined area of ​​the disk 10, where a predetermined interval (gap) is left in the radial direction adjacent to the predetermined track (hereinafter, also referred to as an adjacent track), or by randomly writing data. Furthermore, the read / write control unit 610 can also, upon receiving commands from the host 100, perform tiling recording by overlapping a portion of the track with the next track in the radial direction for each predetermined area of ​​the disk 10 (hereinafter, also referred to as a strip or strip area). Hereinafter, "normal recording" and / or "tiling recording" may be simply represented as "writing." Writing to adjacent tracks of a predetermined track may also be referred to as "edge writing."

[0054] Figure 4 This is a schematic diagram illustrating an example of write processing. Figure 4 The diagram shows the direction of travel in the circumferential direction. There are also cases where the direction in the circumferential direction where the head 15 sequentially writes and reads data relative to the disk 10, that is, the direction in the circumferential direction where the head 15 travels relative to the disk 10, is called the direction of travel. For example, the direction of travel is opposite to the rotation direction of the disk 10. Alternatively, the direction of travel can be the same as the rotation direction of the disk 10. In the circumferential direction, there are also cases where the direction of travel is called the rear direction or simply rear. In the circumferential direction, there are also cases where the direction opposite to the rear direction is called the front direction or simply front. Figure 4 The diagram shows tracks CTRn-1, CTRn, and CTRn+1. Figure 4In this context, for example, tracks CTRn-1, CTRn, and CTRn+1 may have the same track width. Terms such as "same," "identical," "consistent," and "equivalent" encompass both complete identicalness and differences to a degree that can be considered substantially the same. Furthermore, the track widths of tracks CTRn-1 to CTRn+1 may also differ. Figure 4 The diagram shows the center CTCn-1 of track CTRn-1, the center CTCn of track CTRn, and the center CTCn+1 of track CTRn+1. Figure 4 In the example shown, tracks CTRn-1, CTRn, and CTRn+1 are written with track spacing CTP. The track center CTCn-1 of track CTRn-1 is separated from the track center CTCn of track CTRn by track spacing CTP. The track center CTCn of track CTRn is separated from the track center CTCn+1 of track CTRn by track spacing CTP. Tracks CTRn-1 and CTRn are separated by gap GP. Tracks CTRn and CTRn+1 are separated by gap GP. Furthermore, tracks CTRn-1 to CTRn+1 can also be written with different track spacings. Figure 4 For ease of explanation, each track is shown as a rectangular shape extending in the circumferential direction with a predetermined track width, but in reality, it is curved along the circumferential direction. Alternatively, each track can also be wavy, extending in the circumferential direction while varying in the radial direction.

[0055] exist Figure 4 In the example shown, the read / write control unit 610 positions the head 15 at the center of track CTCn-1 in a predetermined area of ​​disk 10 and writes (or normally records) track CTRn-1 or a predetermined sector of track CTRn-1.

[0056] The read / write control unit 610 positions the head 15 at the center CTCn of track CTRn-1, which is located inward from the center CTCn-1 of track CTRn-1 by track spacing CTP, and writes (or normally records) the track CTRn or a predetermined sector of track CTRn.

[0057] The read / write control unit 610 positions the head 15 at the center CTCn+1 of track CTRn, which is located inward from the center CTCn of track CTRn by track spacing CTP, and writes (or normally records) a predetermined sector of track CTRn+1.

[0058] The read / write control unit 610 can sequentially write (or normally record) tracks CTRn-1, CTRn, and CTRn+1 in a predetermined area of ​​disk 10, or randomly write (or normally record) predetermined sectors of track CTRn-1, track CTRn, and track CTRn+1.

[0059] The access processing control unit 620 controls access processing, such as write processing and read processing. Based on evaluation metrics corresponding to the write and read processing characteristics of a predetermined recording area of ​​the disk 10, such as a partition, track, or sector, the access processing control unit 620 controls characteristic values ​​corresponding to write processing (hereinafter, also referred to as write processing parameters or simply parameters). Evaluation metrics include, for example, error rate (bit error rate: BER). Write processing parameters include, for example, recording density (Bits Per Inch: BPI), recording current, a heater setting value equivalent to the value of the current (or voltage) applied to the heater, data transfer speed, and the recording frequency (hereinafter, also referred to as recording frequency) when writing data corresponding to the recording density of the predetermined area. For ease of explanation, the following interpretations are also provided: "BER of data written to a predetermined recording area" is abbreviated as "BER of the predetermined recording area"; "recording density of data written to a predetermined recording area" is abbreviated as "recording density of the predetermined recording area"; "recording current when writing data to a predetermined recording area" is abbreviated as "recording current of the predetermined recording area"; "heater setting value when writing data to a predetermined recording area" is abbreviated as "heater setting value of the predetermined recording area"; "data transfer speed when writing data to a predetermined recording area" is abbreviated as "transfer speed of the predetermined recording area"; and "recording frequency when writing data to a predetermined recording area" is abbreviated as "recording frequency of the predetermined recording area". Evaluation metrics may also include the meaning of the frequency of the signal corresponding to the evaluation metric. BER may also include the meaning of the frequency of the signal corresponding to the BER. Write processing parameters may also include the meaning of the frequency of the signal corresponding to the write processing parameters. Recording density, recording current, heater setting value, transfer speed, or recording frequency may also include the meaning of the frequency of the signal corresponding to the recording density, recording current, heater setting value, transfer speed, or recording frequency.

[0060] The access processing control unit 620 controls the changes in write processing parameters (hereinafter referred to as changes in write processing parameters) of a predetermined track within one week based on changes in evaluation indicators (hereinafter also referred to as changes in evaluation indicators), such as changes in the BER (bit rate) of the track within one week (hereinafter also referred to as changes in BER). These changes include changes in recording density (hereinafter also referred to as changes in recording density), recording current (hereinafter also referred to as changes in recording current), heater setting value (hereinafter also referred to as changes in heater setting value), transfer speed (hereinafter also referred to as changes in transfer speed), or recording frequency (hereinafter also referred to as changes in recording frequency).

[0061] The access processing control unit 620 controls write processing parameters for each predetermined region of a predetermined track, such as the recording density, recording current, heater setting, transfer speed, or recording frequency, based on evaluation metrics for each predetermined region, such as the BER of each divided region of the predetermined track. A divided region corresponds to one of multiple regions divided in the circumferential direction of the predetermined track. A divided region may, for example, be composed of multiple sectors within the predetermined track. Furthermore, the circumferential lengths of the divided regions can be the same or different. In other words, multiple divided regions of the predetermined track can have the same number of sectors or different numbers of sectors. Additionally, a divided region may also correspond to one sector of the predetermined track.

[0062] The access processing control unit 620 controls each write processing parameter of each circumferential position of the predetermined track based on each evaluation index of each circumferential position of the predetermined track, such as each BER of each circumferential position of the predetermined track, such as each recording density, each recording current, each heater setting value, each transfer speed or each recording frequency of each circumferential position of the track.

[0063] The access processing control unit 620 controls the write processing parameters of each sector of the predetermined track based on the evaluation indicators of each sector of the predetermined track, such as the BER of each sector of the predetermined track. These parameters include the recording density, recording current, heater setting value, transfer speed, or recording frequency of each sector of the track.

[0064] The access processing control unit 620 sets the write processing parameters on a predetermined track to a certain write processing parameter (hereinafter also referred to as a reference write processing parameter) as a reference, and measures the change in the evaluation index on that track (hereinafter also referred to as the change in the measured evaluation index). Based on the measured change in the measured evaluation index of that track, the access processing control unit 620 calculates the change in the write processing parameter relative to the reference write processing parameter on that track, used to adjust the change in the measured evaluation index to be uniform or suppressed (hereinafter also referred to as the change in the write processing parameter correction amount or the change in the write processing parameter variation). The access processing control unit 620 adds (or subtracts) the change in the write processing parameter correction amount to the reference write processing parameter on that track. As a result, the access processing control unit 620 corrects (or adjusts) the reference write processing parameter of that track to the change in the write processing parameter of that track (hereinafter also referred to as the change in the corrected write processing parameter or the change in the corrected parameter). The access processing control unit 620 sets the change in the corrected write processing parameter for that track.

[0065] Furthermore, the access processing control unit 620, either idle or in real-time, sets the write processing parameters on a predetermined track as reference write processing parameters and measures the changes in the measured evaluation index on that track. Based on the measured changes in the measured evaluation index of that track, the access processing control unit 620 calculates the change in the write processing parameter correction amount for that track, either idle or in real-time. The access processing control unit 620 adds (or subtracts) the change in the write processing parameter correction amount to the reference write processing parameters on that track, either idle or in real-time. Thus, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of that track to the change in the corrected write processing parameters of that track, either idle or in real-time. The access processing control unit 620 sets the change in the corrected write processing parameters for that track, either idle or in real-time. Additionally, the access processing control unit 620 can also store the changes in each corrected write processing parameter on each track in a predetermined storage area, such as the system area 10b of disk 10 and the non-volatile memory 80.

[0066] For example, the access processing control unit 620 sets the recording density, recording current, heater setting value, transfer speed, or recording frequency on a predetermined track to a certain recording density (hereinafter also referred to as a reference recording density), a certain recording current (hereinafter also referred to as a reference recording current), a certain heater setting value (hereinafter also referred to as a reference heater setting value), a certain transfer speed (hereinafter also referred to as a reference transfer speed), or a certain recording frequency (hereinafter also referred to as a reference recording frequency), and measures the change in BER on that track (hereinafter also referred to as the change in measured BER). Based on the measured BER variation of the track, the access processing control unit 620 calculates the variation of the recording density relative to the reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency on the track, which are used to adjust the variation of the measured BER of the track to be uniform or suppressed. These variations include the variation of the recording density (hereinafter also referred to as the variation of recording density correction amount or the variation of recording density variation), the variation of the recording current (hereinafter also referred to as the variation of recording current correction amount or the variation of recording current variation), the variation of the heater setting value (hereinafter also referred to as the variation of heater setting value correction amount or the variation of heater setting value variation), the variation of the transport speed (hereinafter also referred to as the variation of transport speed correction amount or the variation of transport speed variation), and the variation of the recording frequency (hereinafter also referred to as the variation of recording frequency correction amount or the variation of recording frequency variation). The access processing control unit 620 adds (or subtracts) changes in recording density correction, recording current correction, heater setting correction, transport speed correction, or recording frequency correction to the reference recording density, reference recording current, reference heater setting, reference transport speed correction, or recording frequency correction of the track. As a result, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of the track to changes in recording density (hereinafter, there may also be a case of correcting changes in recording density), recording current (hereinafter, there may also be a case of correcting changes in recording current), heater setting (hereinafter, there may also be a case of correcting changes in heater setting), transport speed (hereinafter, there may also be a case of correcting changes in transport speed), or recording frequency (hereinafter, there may also be a case of correcting changes in recording frequency). The access processing control unit 620 sets corrections for changes in recording density, recording current, heater setting, transport speed, or recording frequency of the track.The access processing control unit 620 can also store changes in correction recording density, correction recording current, correction heater setting, correction transfer speed, or correction recording frequency on each track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0067] The access processing control unit 620 sets each write processing parameter at each circumferential position on a predetermined track as a reference write processing parameter, and measures each evaluation index (hereinafter, also referred to as a measured evaluation index) at each circumferential position of the track. Based on the measured evaluation indexes at each circumferential position of the track, the access processing control unit 620 calculates the amount of change in each write processing parameter at each circumferential position relative to the reference write processing parameters at each circumferential position of the track, used to adjust the measured evaluation indexes at each circumferential position of the track to be uniform or suppressed (hereinafter, also referred to as write processing parameter correction amount or write processing parameter change amount). The access processing control unit 620 adds (or subtracts) the write processing parameter correction amount at each circumferential position to the reference write processing parameters at each circumferential position of the track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters at each circumferential position on the track to write processing parameters at each circumferential position (hereinafter, it may also be referred to as corrected write processing parameters). The access processing control unit 620 sets each corrected write processing parameter corresponding to each circumferential position of the track. The access processing control unit 620 may also store each corrected write processing parameter at each circumferential position of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0068] The changes in evaluation metrics (or measured evaluation metrics) on the predetermined track include the evaluation metrics (or measured evaluation metrics) at each circumferential position of the predetermined track. The changes in write processing parameter corrections on the predetermined track include the write processing parameter corrections at each circumferential position of the predetermined track. The changes in write processing parameters on the predetermined track include the write processing parameters at each circumferential position of the predetermined track. The changes in corrected write processing parameters on the predetermined track include the corrected write processing parameters at each circumferential position of the predetermined track.

[0069] For example, the access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency at each circumferential position on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures each BER at each circumferential position of the track (hereinafter, there may also be a case referred to as measured BER). The access processing control unit 620 calculates, based on the measured BER at each circumferential position of the track, the amount of change in recording density at each circumferential position relative to each reference recording density, each reference recording current, each reference heater setting value, each reference transport speed, or each reference recording frequency at each circumferential position on the track (hereinafter, it may also be called recording density correction amount or recording density change amount), the amount of change in recording current (hereinafter, it may also be called recording current correction amount or recording current change amount), the amount of change in heater setting value (hereinafter, it may also be called heater setting correction amount or heater setting change amount), the amount of change in transport speed (hereinafter, it may also be called transport speed correction amount or transport speed change amount), or the amount of change in recording frequency (hereinafter, it may also be called recording frequency correction amount or recording frequency change amount) for adjusting the measured BER at each circumferential position of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) correction amounts for recording density, recording current, heater setting, transport speed, or recording frequency at each circumferential position on the track to each reference recording density, reference recording current, heater setting, transport speed, or recording frequency. As a result, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency at each circumferential position on the track to the corresponding recording density (hereinafter, also referred to as corrected recording density), recording current (hereinafter, also referred to as corrected recording current), heater setting (hereinafter, also referred to as corrected heater setting), transport speed (hereinafter, also referred to as corrected transport speed), or recording frequency (hereinafter, also referred to as corrected recording frequency) at each circumferential position on the track. The access processing control unit 620 sets the correction recording density, correction recording current, correction heater setting value, correction transfer speed, or correction recording frequency corresponding to each circumferential position of the track. The access processing control unit 620 may also maintain the correction recording density, correction recording current, correction heater setting value, correction transfer speed, or correction recording frequency at each circumferential position of the predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0070] Variations in BER (or measured BER) on a predetermined track include the BER (or measured BER) at each circumferential position of the predetermined track. Variations in recording density on a predetermined track include the recording density at each circumferential position of the predetermined track. Variations in recording density correction on a predetermined track include the recording density correction at each circumferential position of the predetermined track. Variations in corrected recording density on a predetermined track include the corrected recording density at each circumferential position of the predetermined track. Variations in recording current on a predetermined track include the recording current at each circumferential position of the predetermined track. Variations in recording current correction on a predetermined track include the recording current correction at each circumferential position of the predetermined track. Variations in corrected recording current on a predetermined track include the corrected recording current at each circumferential position of the predetermined track. Variations in heater setting on a predetermined track include the heater setting at each circumferential position of the predetermined track. Variations in heater setting correction on a predetermined track include the heater setting correction at each circumferential position of the predetermined track. Variations in the correction heater setting value on the predetermined track include the correction heater setting value at each circumferential position of the predetermined track. Variations in the transport speed on the predetermined track include the transport speed at each circumferential position of the predetermined track. Variations in the transport speed correction amount on the predetermined track include the transport speed correction amount at each circumferential position of the predetermined track. Variations in the corrected transport speed on the predetermined track include the corrected transport speed at each circumferential position of the predetermined track. Variations in the recording frequency on the predetermined track include the recording frequency at each circumferential position of the predetermined track. Variations in the recording frequency correction amount on the predetermined track include the recording frequency correction amount at each circumferential position of the predetermined track. Variations in the corrected recording frequency on the predetermined track include the corrected recording frequency at each circumferential position of the predetermined track.

[0071] The access processing control unit 620 sets the write processing parameters of each partitioned region on a predetermined track as reference write processing parameters and measures each measured evaluation index of each partitioned region of the track. Based on the measured evaluation indexes of each partitioned region of the track, the access processing control unit 620 calculates a correction amount for each partitioned region's write processing parameters relative to the reference write processing parameters of each partitioned region of the track, used to adjust the measured evaluation indexes of each partitioned region of the track to uniformity or suppression. The access processing control unit 620 adds (or subtracts) the correction amount for each partitioned region's write processing parameters to the reference write processing parameters of each partitioned region of the track. Thus, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of each partitioned region of the track to corrected write processing parameters for each partitioned region. The access processing control unit 620 sets corrected write processing parameters corresponding to each partitioned region of the track. The access processing control unit 620 can also store the correction write processing parameters of each partitioned area of ​​the predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0072] Changes in evaluation metrics (or measured evaluation metrics) on a predetermined track include changes in each evaluation metric (or measured evaluation metric) for each sub-region of the predetermined track. Changes in write processing parameters on a predetermined track include changes in each write processing parameter for each sub-region of the predetermined track. Changes in write processing parameter correction amounts on a predetermined track include changes in write processing parameter correction amounts for each sub-region of the predetermined track. Changes in corrected write processing parameters on a predetermined track include corrected write processing parameters for each sub-region of the predetermined track.

[0073] For example, the access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency of each segmented region on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures each BER (hereinafter, also referred to as measured BER) of each segmented region of the track. Based on the measured BER of each segmented region of the track, the access processing control unit 620 calculates a correction amount for each recording density, each recording current, each heater setting, each transport speed, or each recording frequency of each segmented region on the track, relative to the reference recording density, each reference recording current, each reference heater setting value, each reference transport speed, or each reference recording frequency of each segmented region on the track, for adjusting the measured BER of each segmented region of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) correction amounts for the recording density, recording current, heater setting, transport speed, or recording frequency of each segmented region on the track to each reference recording density, reference recording current, reference heater setting, transport speed, or recording frequency. As a result, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of each segmented region on the track to corrected recording density, corrected recording current, corrected heater setting, corrected transport speed, or corrected recording frequency for each segmented region on the track. The access processing control unit 620 sets corrected recording densities, corrected recording currents, corrected heater setting values, corrected transport speeds, or corrected recording frequencies for each segmented region on the track. The access processing control unit 620 can also maintain each correction recording density, each correction recording current, each correction heater setting value, each correction transmission speed, or each correction recording frequency in each divided area of ​​the predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0074] Variations in BER (or measured BER) on a predetermined track include the BER (or measured BER) for each sub-region of the predetermined track. Variations in recording density on a predetermined track include the recording density for each sub-region of the predetermined track. Variations in recording density correction on a predetermined track include the recording density correction for each sub-region of the predetermined track. Variations in corrected recording density on a predetermined track include the corrected recording density for each sub-region of the predetermined track. Variations in recording current on a predetermined track include the recording current for each sub-region of the predetermined track. Variations in recording current correction on a predetermined track include the recording current correction for each sub-region of the predetermined track. Variations in corrected recording current on a predetermined track include the corrected recording current for each sub-region of the predetermined track. Variations in heater setting on a predetermined track include the heater setting for each sub-region of the predetermined track. Variations in heater setting correction on a predetermined track include the heater setting correction for each sub-region of the predetermined track. Variations in corrected heater setting on a predetermined track include the corrected heater setting for each sub-region of the predetermined track. Variations in transport speed on a predetermined track include the transport speeds of each division of the predetermined track. Variations in transport speed correction on a predetermined track include the transport speed corrections of each division of the predetermined track. Variations in corrected transport speed on a predetermined track include the corrected transport speeds of each division of the predetermined track. Variations in recording frequency on a predetermined track include the recording frequencies of each division of the predetermined track. Variations in corrected recording frequency on a predetermined track include the corrected recording frequencies of each division of the predetermined track.

[0075] The access processing control unit 620 sets the write processing parameters of each sector on a predetermined track as reference write processing parameters and measures the measured evaluation indices of each sector on that track. Based on the measured evaluation indices of each sector on that track, the access processing control unit 620 calculates the write processing parameter correction amount for each sector relative to the reference write processing parameters of each sector on that track, used to adjust the measured evaluation indices of each sector on that track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the write processing parameter correction amount for each sector to the reference write processing parameters of each sector on that track. Thus, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of each sector on that track to the write processing parameters of each sector (hereinafter, there may also be cases referred to as corrected write processing parameters). The access processing control unit 620 sets the corrected write processing parameters corresponding to each sector on that track. The access processing control unit 620 can also store the correction and write processing parameters of each sector of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0076] Changes in evaluation metrics (or measured evaluation metrics) on a predetermined track include all evaluation metrics (measured evaluation metrics) for each sector of the predetermined track. Changes in write processing parameters on a predetermined track include all write processing parameters for each sector of the predetermined track. Changes in write processing parameter correction amounts on a predetermined track include all write processing parameter correction amounts for each sector of the predetermined track. Changes in corrected write processing parameters on a predetermined track include all corrected write processing parameters for each sector of the predetermined track.

[0077] For example, the access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency of each sector on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures each measured BER of each sector of the track. Based on the measured BER of each sector of the track, the access processing control unit 620 calculates a correction amount for each sector, a correction amount for each recording density, a correction amount for each recording current, a correction amount for each heater setting, a correction amount for each transport speed, or a correction amount for each recording frequency of each sector on the track, relative to each reference recording density, each reference recording current, each reference heater setting value, each reference transport speed, or each reference recording frequency of each sector on the track, to correct (or adjust) the measured BER of each sector of the track to be uniform. The access processing control unit 620 adds (or subtracts) corrections for the recording density, recording current, heater setting, transport speed, or recording frequency of each sector on the track to each reference recording density, reference recording current, reference heater setting, transport speed, or recording frequency. As a result, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of each sector on the track to each recording density (hereinafter, also referred to as corrected recording density), recording current (hereinafter, also referred to as corrected recording current), heater setting (hereinafter, also referred to as corrected heater setting), transport speed (hereinafter, also referred to as corrected transport speed), or recording frequency (hereinafter, also referred to as corrected recording frequency) of each sector on the track. The access processing control unit 620 sets the correction recording density, correction recording current, correction heater setting value, correction transfer speed, or correction recording frequency corresponding to each sector of the track. The access processing control unit 620 may also store the correction recording density, correction recording current, correction heater setting value, correction transfer speed, or correction recording frequency of each sector of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0078] Variations in BER (or measured BER) on a predetermined track include the BER (or measured BER) of each sector on that predetermined track. Variations in recording density on a predetermined track include the recording density of each sector on that predetermined track. Variations in recording density correction on a predetermined track include the recording density correction of each sector on that predetermined track. Variations in corrected recording density on a predetermined track include the corrected recording density of each sector on that predetermined track. Variations in recording current on a predetermined track include the recording current of each sector on that predetermined track. Variations in recording current correction on a predetermined track include the recording current correction of each sector on that predetermined track. Variations in corrected recording current on a predetermined track include the corrected recording current of each sector on that predetermined track. Variations in heater settings on a predetermined track include the heater settings of each sector on that predetermined track. Variations in heater setting correction on a predetermined track include the heater setting correction of each sector on that predetermined track. Variations in corrected heater settings on a predetermined track include the corrected heater settings of each sector on that predetermined track. Variations in the transfer speed on a predetermined track include the transfer speed of each sector of the predetermined track. Variations in the transfer speed correction amount on a predetermined track include the transfer speed correction amount of each sector of the predetermined track. Variations in the corrected transfer speed on a predetermined track include the corrected transfer speed of each sector of the predetermined track. Variations in the recording frequency on a predetermined track include the recording frequency of each sector of the predetermined track. Variations in the recording frequency correction amount on a predetermined track include the recording frequency correction amount of each sector of the predetermined track. Variations in the corrected recording frequency on a predetermined track include the corrected recording frequency of each sector of the predetermined track.

[0079] The access processing control unit 620 sets the write processing parameters on a predetermined track as the reference write processing parameters and measures the variation of the measured evaluation index of that track. The access processing control unit 620 approximates the measured variation of the measured evaluation index of that track and calculates the approximate variation of the measured evaluation index of that track (hereinafter, there may also be a case referred to as the variation of the approximate evaluation index). The access processing control unit 620 corrects (or adjusts) the calculated variation of the approximate evaluation index of that track and calculates the corrected (or adjusted) variation of the approximate evaluation index of that track (hereinafter, there may also be a case referred to as the variation of the corrected evaluation index). Based on the calculated variation of the corrected evaluation index of that track, the access processing control unit 620 calculates a write processing parameter correction amount relative to the reference write processing parameters on that track, used to adjust the variation of the corrected evaluation index on that track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the variation of the write processing parameter correction amount to the reference write processing parameters on that track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of the track to a change in the corrected write processing parameters of the track. The access processing control unit 620 sets the change in the corrected write processing parameters for the track. The access processing control unit 620 may also store the change in the corrected write processing parameters on a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0080] Furthermore, the access processing control unit 620, either idle or in real-time, sets the write processing parameters on a predetermined track as reference write processing parameters and measures the variation of the measured evaluation index of that track. The access processing control unit 620, either idle or in real-time, approximates the measured variation of the track's measured evaluation index and calculates the approximate variation of the track's approximate evaluation index. The access processing control unit 620, either idle or in real-time, corrects (or adjusts) the calculated variation of the track's approximate evaluation index and calculates the corrected (or adjusted) variation of the track's corrected evaluation index. Based on the calculated variation of the track's corrected evaluation index, the access processing control unit 620, either idle or in real-time, calculates a write processing parameter correction amount relative to the reference write processing parameters on that track to correct (or adjust) the variation of the corrected evaluation index to a uniform level. The access processing control unit 620, either idle or in real-time, adds (or subtracts) the variation of the write processing parameter correction amount to the reference write processing parameters on that track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of the track to the modified write processing parameters of the track, either when idle or in real time. The access processing control unit 620 sets the modified write processing parameters for the track, either when idle or in real time. Additionally, the access processing control unit 620 can also store the changes in the modified write processing parameters of each track in a predetermined storage area, such as the system area 10b of disk 10 and the non-volatile memory 80, either when idle or in real time.

[0081] The access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures the variation in the measured BER of that track. The access processing control unit 620 approximates the measured variation in the measured BER of that track and calculates the approximate variation in the measured BER of that track (hereinafter, there may also be a case referred to as the approximate BER variation). The access processing control unit 620 corrects (or adjusts) the calculated approximate BER variation of that track and calculates the corrected (or adjusted) approximate BER variation of that track (hereinafter, there may also be a case referred to as the corrected BER variation). Based on the calculated variation in the corrected BER of the track, the access processing control unit 620 calculates variations in recording density correction, recording current correction, heater setting correction, transport speed correction, or recording frequency correction relative to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of the track, used to adjust the variation in the corrected BER of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the variations in recording density correction, recording current correction, heater setting correction, transport speed correction, or recording frequency correction to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of the track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of the track to the variations in the corrected recording density, corrected recording current, corrected heater setting, corrected transport speed, or corrected recording frequency of the track. The access processing control unit 620 sets corrections for changes in recording density, recording current, heater setting, transfer speed, or recording frequency for each track. The access processing control unit 620 can also store these corrections for changes in recording density, recording current, heater setting, transfer speed, or recording frequency for each track in a predetermined storage area, such as the system area 10b of disk 10 or the non-volatile memory 80.

[0082] For example, the access processing control unit 620 sets the recording density on a predetermined track as a reference recording density and measures the variation in the measured BER of that track. The access processing control unit 620 approximates the measured variation in the measured BER of the track and calculates the approximate BER for each circumferential position of the track. The access processing control unit 620 corrects (or adjusts) the calculated variation in the approximate BER of the track and calculates the corrected (or adjusted) variation in the track's BER. Based on the calculated variation in the corrected BER of the track, the access processing control unit 620 calculates the variation in the track's recording density correction amount relative to the reference recording density of the track, used to adjust the variation in the corrected BER of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the recording density correction amount for each circumferential position to the reference recording density of the track. Thus, the access processing control unit 620 adds (or subtracts) the variation in the track's recording density correction amount to the reference recording density of the track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density of the track to the change in the recording density correction amount of the track, and the change in the corrected recording density of the track. The access processing control unit 620 calculates the change in the time base generator (TBG) value (hereinafter, there is also a case referred to as the change in TBG value) corresponding to the change in the recording frequency (corrected recording frequency) proportional to the change in the corrected recording density on the track. The access processing control unit 620 sets the change in the TBG value for the track. The access processing control unit 620 may also store the change in the TBG value on a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and the non-volatile memory 80.

[0083] The access processing control unit 620 sets each write processing parameter at each circumferential position on a predetermined track as a reference write processing parameter, and measures each measured evaluation index at each circumferential position of the track. The access processing control unit 620 approximates each measured evaluation index at each circumferential position of the track, and calculates each approximate evaluation index at each circumferential position of the track after approximation. The access processing control unit 620 corrects (or adjusts) each approximate evaluation index at each circumferential position of the track, and calculates each corrected evaluation index at each circumferential position of the track after correction (or adjustment). Based on the calculated corrected evaluation index at each circumferential position of the track, the access processing control unit 620 calculates a correction amount for each write processing parameter at each circumferential position relative to the reference write processing parameters at each circumferential position of the track, used to adjust the correction evaluation index at each circumferential position of the track to uniformity or suppression. The access processing control unit 620 adds (or subtracts) the correction amount of each write processing parameter at each circumferential position on the track to the reference write processing parameters at each circumferential position. Thus, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters at each circumferential position on the track to corrected write processing parameters for each circumferential position. The access processing control unit 620 sets each corrected write processing parameter corresponding to each circumferential position of the track. The access processing control unit 620 may also store each corrected write processing parameter at each circumferential position of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0084] The changes in the approximate evaluation indexes on the predetermined track include the approximate evaluation indexes for each circumferential position of the predetermined track. The changes in the corrected evaluation indexes on the predetermined track include the corrected evaluation indexes for each circumferential position of the predetermined track.

[0085] For example, the access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency at each circumferential position on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures each measured BER at each circumferential position of the track. The access processing control unit 620 approximates each measured BER at each circumferential position of the track and calculates each approximate BER at each circumferential position of the track. The access processing control unit 620 corrects (or adjusts) each approximate BER at each circumferential position of the track and calculates each corrected (or adjusted) BER at each circumferential position of the track. Based on the calculated correction BER at each circumferential position on the track, the access processing control unit 620 calculates a correction amount for each circumferential position of the track, relative to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency, for adjusting the correction BER at each circumferential position of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the correction amounts for each circumferential position of the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transfer speed, or reference recording frequency at each circumferential position on the track to corrected recording densities, corrected recording currents, corrected heater settings, corrected transfer speeds, or corrected recording frequencies at each circumferential position on the track. The access processing control unit 620 sets corrected recording densities, corrected recording currents, corrected heater settings, corrected transfer speeds, or corrected recording frequencies corresponding to each circumferential position on the track. The access processing control unit 620 may also maintain the corrected recording densities, corrected recording currents, corrected heater settings, corrected transfer speeds, or corrected recording frequencies at each circumferential position on a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and the non-volatile memory 80.

[0086] Variations in the approximate BER on a predetermined track include the approximate BER at each circumferential position of the predetermined track. Variations in the corrected BER on a predetermined track include the corrected BER at each circumferential position of the predetermined track.

[0087] For example, the access processing control unit 620 sets the recording density of each circumferential position on a predetermined track as a reference recording density and measures the measured BER of each circumferential position on the track. The access processing control unit 620 approximates the measured BER of each circumferential position on the track and calculates the approximate BER of each circumferential position on the track. The access processing control unit 620 corrects (or adjusts) the calculated approximate BER of each circumferential position on the track and calculates the corrected BER of each circumferential position on the track. Based on the calculated corrected BER of each circumferential position on the track, the access processing control unit 620 calculates a recording density correction amount for each circumferential position relative to the reference recording density of each circumferential position on the track, used to adjust the corrected BER of each circumferential position on the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) a correction amount for each circumferential position of the reference recording density at each circumferential position on the track. Thus, the access processing control unit 620 corrects (or adjusts) the reference recording density at each circumferential position of the track to a corrected recording density for each circumferential position. The access processing control unit 620 calculates a TBG value for each circumferential position that corresponds to a recording frequency (corrected recording frequency) proportional to the corrected recording density at each circumferential position on the track. The access processing control unit 620 sets a TBG value corresponding to each circumferential position of the track. The access processing control unit 620 may also store the TBG values ​​at each circumferential position of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and the non-volatile memory 80.

[0088] The variation of TBG value on the predetermined track includes the TBG value at each circumferential position of the predetermined track.

[0089] The access processing control unit 620 sets the write processing parameters of each partitioned region on a predetermined track as reference write processing parameters and measures each measured evaluation index of each partitioned region of the track. The access processing control unit 620 approximates the measured evaluation indexes of each partitioned region of the track and calculates the approximate evaluation indexes of each partitioned region of the track. The access processing control unit 620 corrects (or adjusts) the calculated approximate evaluation indexes of each partitioned region of the track and calculates the corrected (or adjusted) evaluation indexes of each partitioned region of the track. Based on the calculated corrected evaluation indexes of each partitioned region of the track, the access processing control unit 620 calculates the write processing parameter correction amount for each partitioned region relative to the reference write processing parameters of each partitioned region on the track, used to adjust the corrected evaluation indexes of each partitioned region of the track to uniformity or suppression. The access processing control unit 620 adds (or subtracts) the write processing parameter correction amount for each partitioned region to the reference write processing parameters of each partitioned region on the track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of each partitioned region on the track to the corrected write processing parameters of each partitioned region. The access processing control unit 620 sets the corrected write processing parameters corresponding to each partitioned region of the track. The access processing control unit 620 may also store the corrected write processing parameters of each partitioned region of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0090] Changes in the approximate evaluation indexes on the predetermined track include the approximate evaluation indexes for each sub-region of the predetermined track. Changes in the revised evaluation indexes on the predetermined track include the revised evaluation indexes for each sub-region of the predetermined track.

[0091] For example, the access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency of each segmented region on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures each measured BER of each segmented region of the track. The access processing control unit 620 approximates each measured BER of each segmented region of the track and calculates each approximate BER of each segmented region of the track after approximation. The access processing control unit 620 corrects (or adjusts) each approximate BER of each segmented region of the track and calculates each corrected BER of each segmented region of the track after correction (or adjustment). Based on the calculated correction BER of each segmented region on the track, the access processing control unit 620 calculates a correction amount for each recording density, recording current, heater setting, transport speed, or recording frequency relative to the reference recording density, reference recording current, reference heater setting, transport speed, or recording frequency of each segmented region on the track, used to adjust the correction BER of each segmented region of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the correction amounts for each recording density, recording current, heater setting, transport speed, or recording frequency of each segmented region on the track to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of each segmented region. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transfer speed, or reference recording frequency of each segmented region on the track to the corrected recording density, corrected recording current, corrected heater setting, corrected transfer speed, or corrected recording frequency of each segmented region on the track. The access processing control unit 620 sets the corrected recording density, corrected recording current, corrected heater setting, corrected transfer speed, or corrected recording frequency corresponding to each circumferential position on the track. The access processing control unit 620 may also maintain the corrected recording density, corrected recording current, corrected heater setting, corrected transfer speed, or corrected recording frequency of each segmented region on a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0092] Variations in the approximate BER on a predetermined track include the approximate BER at each circumferential position of the predetermined track. Variations in the corrected BER on a predetermined track include the corrected BER at each circumferential position of the predetermined track.

[0093] For example, the access processing control unit 620 sets the recording density of each segmented region on a predetermined track as a reference recording density and measures the measured BER of each segmented region on that track. The access processing control unit 620 approximates the measured BER of each segmented region on that track and calculates the approximate BER of each segmented region on that track. The access processing control unit 620 corrects (or adjusts) the calculated approximate BER of each segmented region on that track and calculates the corrected BER of each segmented region on that track. Based on the calculated corrected BER of each segmented region on that track, the access processing control unit 620 calculates a recording density correction amount for each segmented region relative to the reference recording density of each segmented region on that track, used to adjust the corrected BER of each segmented region on that track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the recording density correction amount for each segmented region to the reference recording density of each segmented region on that track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density of each partitioned region on the track to the corrected recording density of each partitioned region. The access processing control unit 620 calculates the TBG value of each partitioned region, which is proportional to the corrected recording density of each partitioned region on the track. The access processing control unit 620 sets the TBG value corresponding to each partitioned region of the track. The access processing control unit 620 may also store the TBG values ​​of each partitioned region of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and the non-volatile memory 80.

[0094] The variation in TBG values ​​on a predetermined track includes the TBG values ​​of each division of the predetermined track.

[0095] The access processing control unit 620 sets the write processing parameters of each sector on a predetermined track as reference write processing parameters and measures the measured evaluation indexes of each sector on that track. The access processing control unit 620 approximates the measured evaluation indexes of each sector on that track and calculates the approximate evaluation indexes of each sector on that track. The access processing control unit 620 corrects (or adjusts) the calculated approximate evaluation indexes of each sector on that track and calculates the corrected (or adjusted) evaluation indexes of each sector on that track. Based on the calculated corrected evaluation indexes of each sector on that track, the access processing control unit 620 calculates the write processing parameter correction amount for each sector relative to the reference write processing parameters of each sector on that track, used to adjust the corrected evaluation indexes of each sector on that track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the write processing parameter correction amount for each sector to the reference write processing parameters of each sector on that track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of each sector on the track to the corrected write processing parameters of each sector. The access processing control unit 620 sets the corrected write processing parameters corresponding to each sector of the track. The access processing control unit 620 may also store the corrected write processing parameters of each sector of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0096] Changes in the approximate evaluation indexes on the predetermined track include the approximate evaluation indexes for each sector of the predetermined track. Changes in the corrected evaluation indexes on the predetermined track include the corrected evaluation indexes for each sector of the predetermined track.

[0097] For example, the access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency of each sector on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures each measured BER of each sector of that track. The access processing control unit 620 approximates each measured BER of each sector of that track and calculates each approximate BER of each sector of that track. The access processing control unit 620 corrects (or adjusts) each approximate BER of each sector of that track and calculates each corrected BER of each sector of that track. Based on the calculated correction BER of each sector on the track, the access processing control unit 620 calculates the correction amounts for each sector of the track relative to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of each sector on the track, used to adjust the correction BER of each sector of the track to be uniform or suppressed. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transfer speed, or reference recording frequency of each sector on the track to the corrected recording density, corrected recording current, corrected heater setting, corrected transfer speed, or corrected recording frequency of each sector on the track. The access processing control unit 620 sets the corrected recording density, corrected recording current, corrected heater setting, corrected transfer speed, or corrected recording frequency corresponding to each sector on the track. The access processing control unit 620 may also store the corrected recording density, corrected recording current, corrected heater setting, corrected transfer speed, or corrected recording frequency of each sector on a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0098] The variation in approximate BER on a predetermined track includes the approximate BER for each sector of the predetermined track. The variation in corrected BER on a predetermined track includes the corrected BER for each sector of the predetermined track.

[0099] For example, the access processing control unit 620 sets the recording density of each sector on a predetermined track as a reference recording density and measures the measured BER of each sector on that track. The access processing control unit 620 approximates the measured BER of each sector on that track and calculates the approximate BER of each sector on that track. The access processing control unit 620 corrects (or adjusts) the calculated approximate BER of each sector on that track and calculates the corrected BER of each sector on that track. Based on the calculated corrected BER of each sector on that track, the access processing control unit 620 calculates a recording density correction amount for each sector relative to the reference recording density of each sector on that track, used to adjust the corrected BER of each sector on that track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the recording density correction amount for each sector to the reference recording density of each sector on that track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density of each sector on the track to the corrected recording density of each sector. The access processing control unit 620 calculates the TBG value of each sector, which is proportional to the corrected recording density of each sector on the track. The access processing control unit 620 sets the TBG value corresponding to each sector of the track. The access processing control unit 620 may also store the TBG values ​​of each sector of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and the non-volatile memory 80.

[0100] The variation in TBG value on a predetermined track includes the TBG value of each sector of the predetermined track.

[0101] The access processing control unit 620 sets each write processing parameter at each circumferential position on a predetermined track as a reference write processing parameter, and measures each measured evaluation index at each circumferential position of the track. The access processing control unit 620 approximates each measured evaluation index at each circumferential position of the track, and calculates each approximate evaluation index at each circumferential position of the track after approximation. The access processing control unit 620 corrects (or adjusts) each approximate evaluation index at each circumferential position of the track, and calculates each corrected evaluation index for each segmented region of the track after correction (or adjustment). Based on the calculated corrected evaluation indexes for each segmented region of the track, the access processing control unit 620 calculates a correction amount for each segmented region of the write processing parameters relative to the reference write processing parameters for each segmented region of the track, used to adjust the correction evaluation indexes for each segmented region of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the correction amount for each segmented region of the write processing parameters to the reference write processing parameters for each segmented region of the track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference write processing parameters of each partitioned region on the track to the corrected write processing parameters of each partitioned region. The access processing control unit 620 sets the corrected write processing parameters corresponding to each partitioned region of the track. The access processing control unit 620 may also store the corrected write processing parameters of each partitioned region of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0102] For example, the access processing control unit 620 sets each recording density, each recording current, each heater setting value, each transport speed, or each recording frequency at each circumferential position on a predetermined track as a reference recording density, reference recording current, reference heater setting value, reference transport speed, or reference recording frequency, and measures each measured BER at each circumferential position of the track. The access processing control unit 620 approximates each measured BER at each circumferential position of the track and calculates each approximate BER at each circumferential position of the track after approximation. The access processing control unit 620 corrects (or adjusts) each approximate BER at each circumferential position of the track and calculates each corrected BER for each divided region of the track after correction (or adjustment). Based on the calculated correction BER of each segmented region of the track, the access processing control unit 620 calculates correction amounts for each recording density, recording current, heater setting, transport speed, or recording frequency of each segmented region of the track, relative to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of each segmented region on the track, for adjusting the correction BER of each segmented region of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the correction amounts for each recording density, recording current, heater setting, transport speed, or recording frequency of each segmented region on the track to the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of each segmented region. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density, reference recording current, reference heater setting, reference transport speed, or reference recording frequency of each segmented region on the track to the corrected recording density, corrected recording current, corrected heater setting, corrected transport speed, or corrected recording frequency of each segmented region. The access processing control unit 620 sets the correction recording density, correction recording current, correction heater setting value, correction transfer speed, or correction recording frequency corresponding to each division region of the track. The access processing control unit 620 may also store the correction recording density, correction recording current, correction heater setting value, correction transfer speed, or correction recording frequency in each division region of the predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0103] For example, the access processing control unit 620 sets the recording density of each circumferential position on a predetermined track as a reference recording density and measures the measured BER of each circumferential position on the track. The access processing control unit 620 approximates the measured BER of each circumferential position on the track and calculates the approximate BER of each circumferential position on the track. The access processing control unit 620 corrects (or adjusts) the calculated approximate BER of each circumferential position on the track and calculates the corrected BER of each segmented region of the track. Based on the calculated corrected BER of each segmented region on the track, the access processing control unit 620 calculates a recording density correction amount for each segmented region relative to the reference recording density of each segmented region on the track, used to adjust the corrected BER of each segmented region of the track to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the recording density correction amount of each segmented region to the reference recording density of each segmented region on the track. Therefore, the access processing control unit 620 corrects (or adjusts) the reference recording density of each partitioned region on the track to the corrected recording density of each partitioned region. The access processing control unit 620 calculates the TBG value of each partitioned region on the track. The access processing control unit 620 sets the TBG value corresponding to each partitioned region on the track. The access processing control unit 620 may also store the TBG values ​​of each partitioned region of a predetermined track in a predetermined storage area, such as the system area 10b of disk 10 and non-volatile memory 80.

[0104] Figure 5 This is a schematic diagram illustrating an example of the variation of the measured evaluation index MBL5, the variation of the approximate evaluation index ABL5, and the variation of the corrected evaluation index CBL5 for the circumferential position of a predetermined magnetic track. Figure 5 In the diagram, the vertical axis represents the BER (Breakpoint Requirement), and the horizontal axis represents the circumferential position. Figure 5 On the vertical axis, BER increases as it moves toward the front of the arrow and decreases as it moves toward the opposite side of the arrow. Figure 5 The circumferential position of the horizontal axis includes the circumferential position where data writing begins on the predetermined track (hereinafter, it may also be called the start position) and the circumferential position where data writing ends on the predetermined track (hereinafter, it may also be called the end position). The start position and the end position may be the same or different in the circumferential direction of the predetermined track. Figure 5The diagram shows variations in measured evaluation indices for circumferential positions on a predetermined track (hereinafter, also simply referred to as variations in measured evaluation indices), such as variations in measured BER for circumferential positions (hereinafter, also simply referred to as variations in measured BER) MBL5; variations in approximate evaluation indices for circumferential positions on a predetermined track (hereinafter, also simply referred to as variations in approximate evaluation indices), such as variations in approximate BER for circumferential positions (hereinafter, also simply referred to as variations in approximate BER) ABL5; and variations in corrected evaluation indices for circumferential positions on a predetermined track (hereinafter, also simply referred to as variations in corrected evaluation indices), such as variations in corrected BER for circumferential positions (hereinafter, also simply referred to as variations in corrected BER) CBL5. Additionally, in Figure 5 The front side of the horizontal axis shows the maximum (Max) and average (Ave.) of the measured BER variation, the maximum (Max) and average (Ave.) of the approximate BER variation, and the maximum (Max) and average (Ave.) of the corrected BER variation.

[0105] exist Figure 5 In the example shown, the access processing control unit 620 sets the recording density of each circumferential position on a predetermined track, such as the track currently being accessed (hereinafter, there may also be a case called the track on-track), as the reference recording density, measures each measured BER at each circumferential position on the track, and obtains the variation MBL5 of the measured BER of the track.

[0106] The access processing control unit 620 uses the formula (1) described below to approximate each measured BER of each circumferential position of the track, calculates each approximate BER of each circumferential position of the track after approximation, and obtains the variation ABL5 of the approximate BER of the track.

[0107] ya=a×cos(px1+b)+ca (1)

[0108] Here, ya is the approximate BER, p is the coefficient, x1 is the measured BER, a is the coefficient, b is the coefficient, and ca is the average value of the variation of the approximate BER of the predetermined track ABL5.

[0109] The access processing control unit 620 uses the formula (2) described below to correct (or adjust) each approximate BER of each circumferential position of the track, calculates each corrected BER of each circumferential position of the track after correction (or adjustment), and obtains the change CBL5 of the corrected BER of the track.

[0110] yc=x+cv (2)

[0111] Here, yc is the corrected BER, and cv is the correction amount. The correction amount cv can be calculated using the following formula (3).

[0112] cv=x2-ca (3)

[0113] Here, x2 is the approximate BER.

[0114] Figure 6 This is a schematic diagram illustrating an example of the variation CBL6 of the correction evaluation index for circumferential position and the variation CPL6 of the correction write processing parameter in this embodiment. Figure 6 In the diagram, the vertical axis represents BER and write processing parameters, and the horizontal axis represents the circumferential position. Figure 6 In the diagram, BER increases as it moves towards the tip of the larger arrow and decreases as it moves towards the tip of the smaller arrow. Figure 6 In the text, the write processing parameters increase as you move towards the front of the larger arrow and decrease as you move towards the front of the smaller arrow. Figure 6 The circumferential position of the horizontal axis includes the start position and the end position. Figure 6 The diagram shows the following: reference write processing parameters, such as reference recording density DPL6; variations in corrected write processing parameters for circumferential position (hereinafter also referred to as variations in corrected write processing parameters), such as variations in corrected recording density for circumferential position (hereinafter also referred to as variations in corrected recording density) CPL6; variations in corrected evaluation index (or measured evaluation index) for circumferential position (hereinafter also referred to as variations in corrected evaluation index (or measured evaluation index)), such as variations in corrected BER (or measured BER) for circumferential position (hereinafter also referred to as variations in corrected BER (or measured BER)) MBL6; and variations in evaluation index for circumferential position corresponding to variations in corrected write processing parameters (hereinafter also referred to as variations in suppression evaluation index), such as variations in measured BER for circumferential position corresponding to the variation in corrected recording density CPL6 (hereinafter also referred to as variations in suppression BER) SBL6.

[0115] exist Figure 6In the example shown, the access processing control unit 620 sets the recording density on the current track as the reference recording density and measures the variation in BER (bit difference) MBL6 on the current track. Based on the measured variation in BER MBL6, the access processing control unit 620 calculates a change in the recording density correction amount on the current track to adjust the variation in BER MBL6 to be uniform or suppressed. The access processing control unit 620 adds (or subtracts) the change in recording density correction amount to the reference recording density on the current track. Thus, the access processing control unit 620 corrects (or adjusts) the reference recording density DPL6 on the current track to the change in corrected recording density CPL6 on the current track. The access processing control unit 620 sets the change in corrected recording density CPL6 on the current track. Figure 6 As shown, on the track, by setting the change in recording density CPL6, the change in measured BER MBL6 is suppressed to the change in BER SBL6.

[0116] exist Figure 6 In the example shown, the access processing control unit 620 sets each recording density on the current track as a reference recording density DPL6 and measures the variation in the measured BER of the current track. The access processing control unit 620 approximates the measured variation in the measured BER of the current track and calculates the approximate variation in the BER of the current track. The access processing control unit 620 corrects (or adjusts) the calculated variation in the approximate BER of the current track and calculates the corrected (or adjusted) variation in the corrected BER of the current track MBL6. Based on the calculated variation in the corrected BER of the current track MBL6, the access processing control unit 620 calculates a change in the recording density correction amount used to adjust the variation in the corrected BER of the current track MBL6 to uniformity or suppression. The access processing control unit 620 adds (or subtracts) the change in the recording density correction amount to the reference recording density of the current track. Thus, the access processing control unit 620 corrects (or adjusts) the reference recording density of the current track to the variation in the corrected recording density of the current track CPL6. The access processing control unit 620 sets a correction recording density variation CPL6 for the current track. For example... Figure 6 As shown, on the track, by setting the change in modified recording density CPL6, the change in modified BER MBL6 is suppressed to the change in suppressed BER SBL6.

[0117] Figure 7 This is a schematic diagram illustrating an example of the variation in BER (BER) of a predetermined track for a circumferential position when edge writing has been performed. Figure 7 In the diagram, the vertical axis represents the BER (Breakpoint Requirement), and the horizontal axis represents the circumferential position. Figure 7 In the diagram, BER increases as it moves toward the front of the larger arrow and decreases as it moves toward the front of the smaller arrow. Figure 7 The circumferential position of the horizontal axis includes the start position and the end position. Figure 7 The diagram illustrates changes in modified evaluation metrics (or measured evaluation metrics), such as changes in modified BER (or measured BER) MBL6, and changes in suppression evaluation metrics, such as changes in suppressed BER SBL6. Additionally, Figure 7 The diagram shows the changes in the evaluation index for the circumferential position of the track where the track containing the modified evaluation index (or measured evaluation index), such as the change in modified BER (or measured BER), are shown in DFBL7, and the changes in the evaluation index for the circumferential position of the track where the track containing the modified evaluation index (or measured BER), such as the change in modified BER (or measured BER), are shown in CFBL7, and the changes in the evaluation index for the circumferential position of the track where the track containing the modified BER, such as the change in modified BER, are shown in CFBL7, when the track containing the modified evaluation index (or measured BER), such as the change in modified BER, are shown in CFBL7, when the track containing the modified evaluation index (or measured BER), is shown in CFBL7, when the track containing the modified BER, such as the change in modified BER, are shown in CFBL7, when the track containing the modified BER, such as the change in modified BER, are shown in CFBL7, when the track containing the modified BER, such as the change in modified BER, are shown in CFBL7.

[0118] exist Figure 7 In the example shown, the access processing control unit 620 measures the variation of the measured BER (MBL6) on the track where a reference recording density (DPL6) is set. When the access processing control unit 620 performs an edge write to an adjacent track of the track where the measured BER variation (MBL6) is located, it measures the variation of the initial edge BER (DFBL7).

[0119] exist Figure 7 In the example shown, when the access processing control unit 620 sets a change in the modified recording density CPL6 for the current track, it measures the change in the suppressed BER SBL6 on the current track. When the access processing control unit 620 writes to an adjacent track of the current track with the changed BER SBL6, it measures the change in the modified edge BER CFBL7.

[0120] like Figure 7 As shown, the change in edge BER CFBL7 after correction is greater than the change in edge BER DFBL7 of the initial edge BER. Figure 7In the example shown, a portion of the corrected edge BER change CFBL7 is larger than a portion of the initial edge BER change DFBL7, and a portion of the corrected edge BER change CFBL7 is smaller than a portion of the initial edge BER change DFBL. Therefore, compared to the case where a write was made to a track adjacent to the track containing the measured BER change MBL6, the case where a write was made to a track adjacent to the track containing the suppressed BER change SBL6 may result in a larger effect (Adjacent Track Interference: ATI) from the first 15 of the predetermined region of the track and a smaller ATI from the first 15 of other regions of the track. In other words, compared to the case where a write was made to a track adjacent to the track containing the suppressed BER change SBL6, the case where a write was made to a track adjacent to the track containing the measured BER change MBL6 may result in data in the predetermined region of the track being more prone to degradation and data in other regions of the track being less prone to degradation. In other words, compared to writing data to an adjacent track of the track after the write processing parameters have been corrected, writing data to an adjacent track of the track without correction may result in data degradation in a predetermined area of ​​the track, while data in other areas of the track may not degrade as easily.

[0121] The refresh control unit 630 counts the number of times data is written (hereinafter, also referred to as the number of writes). The refresh control unit 630 also counts the number of times data is written to a region (hereinafter, also referred to as a proximity region) located within a predetermined radius from the target region (hereinafter, also referred to as the target region). For example, the refresh control unit 630 counts the number of times data is written to a proximity region (hereinafter, also referred to as an outer-direction proximity region) located within a predetermined radius from the target region in the outward direction. Additionally, the refresh control unit 630 counts the number of times data is written to a proximity region (hereinafter, also referred to as an inner-direction proximity region) located within a predetermined radius from the target region in the inward direction. The refresh control unit 630 can also store the number of writes as a table in a predetermined recording area, such as the system area 10b of disk 10, volatile memory 70, non-volatile memory 80, or buffer memory 90.

[0122] When the refresh control unit 630 writes data to a proximity region located within a predetermined radius from the target region, it increases the number of writes to the proximity region by a predetermined value. For example, when writing data to a proximity region located within a predetermined radius from the target region, the refresh control unit 630 increases the number of writes to the proximity region by 1. When the refresh control unit 630 writes data to a proximity region in the outward direction, it increases the number of writes to the proximity region in the outward direction by a predetermined value. For example, when writing data to a proximity region in the outward direction, the refresh control unit 630 increases the number of writes to the proximity region in the outward direction by 1. When the refresh control unit 630 writes data to a proximity region in the inward direction, it increases the number of writes to the proximity region in the inward direction by a predetermined value. For example, when writing data to a proximity region in the inward direction, the refresh control unit 630 increases the number of writes to the proximity region in the inward direction by 1.

[0123] The refresh control unit 630 counts the number of times data is written to a region adjacent to the object region in the radial direction (hereinafter also referred to as an adjacent region). For example, the refresh control unit 630 counts the number of times data is written to an adjacent region (hereinafter also referred to as an outer adjacent region) that is adjacent to the object region in the outer direction. Additionally, the refresh control unit 630 counts the number of times data is written to an adjacent region (hereinafter also referred to as an inner adjacent region) that is adjacent to the object region in the inner direction.

[0124] When the refresh control unit 630 writes data to an adjacent region located in the radial direction of the target region, it increases the number of writes to the adjacent region by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an adjacent region located in the radial direction of the target region, it increases the number of writes to the adjacent region by 1 (increment). When the refresh control unit 630 writes data to an adjacent region in the outward direction, it increases the number of writes to the adjacent region in the outward direction (outward write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an adjacent region in the outward direction, it increases the number of writes to the adjacent region in the outward direction (outward write count) by 1 (increment). When the refresh control unit 630 writes data to an adjacent region in the inward direction, it increases the number of writes to the adjacent region in the inward direction (inward write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an adjacent region in the inward direction, it increases the number of writes to the adjacent region in the inward direction (inward write count) by 1 (increment).

[0125] The refresh control unit 630 counts the number of times data is written to a region located within a predetermined radius in the radial direction of the region to which the object is defined (hereinafter, there may also be a region near the object region). For example, the refresh control unit 630 counts the number of times data is written to a region located within a predetermined radius in the outer direction of the object region. Additionally, the refresh control unit 630 counts the number of times data is written to a region located within a predetermined radius in the inner direction of the object region.

[0126] When the refresh control unit 630 writes data to a near-divided region located within a predetermined radius from the object's partitioned region, it increases the number of writes to the near-divided region by a predetermined value (increment). For example, when the refresh control unit 630 writes data to a near-divided region located within a predetermined radius from the object's partitioned region, it increases the number of writes to the near-divided region by 1 (increment). When the refresh control unit 630 writes data to a near-divided region in the outer direction, it increases the number of writes to the near-divided region in the outer direction (outer direction write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to a near-divided region in the outer direction, it increases the number of writes to the near-divided region in the outer direction (outer direction write count) by 1 (increment). When the refresh control unit 630 writes data to a near-divided region in the inner direction, it increases the number of writes to the near-divided region in the inner direction (inner direction write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to a near-divided region in the inner direction, it increases the number of writes to the near-divided region in the inner direction (inner direction write count) by 1 (increment).

[0127] The refresh control unit 630 counts the number of times data is written to a partitioned region that is radially adjacent to the object partitioned region (hereinafter also referred to as an adjacent partitioned region). For example, the refresh control unit 630 counts the number of times data is written to an adjacent partitioned region that is radially adjacent to the object partitioned region (hereinafter also referred to as an outer adjacent partitioned region). Additionally, the refresh control unit 630 counts the number of times data is written to an adjacent partitioned region that is radially adjacent to the object partitioned region (hereinafter also referred to as an outer adjacent partitioned region).

[0128] When the refresh control unit 630 writes data to an adjacent partitioned region located in the radial direction of the object partitioned region, it increases the number of writes to the adjacent partitioned region by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an adjacent partitioned region located in the radial direction of the object partitioned region, it increases the number of writes to the adjacent partitioned region by 1 (increment). When the refresh control unit 630 writes data to an adjacent partitioned region in the outward direction, it increases the number of writes to the adjacent partitioned region in the outward direction (outward write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an adjacent partitioned region in the outward direction, it increases the number of writes to the adjacent partitioned region in the outward direction (outward write count) by 1 (increment). When the refresh control unit 630 writes data to an adjacent partitioned region in the inward direction, it increases the number of writes to the adjacent partitioned region in the inward direction (inward write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an adjacent partitioned region in the inward direction, it increases the number of writes to the adjacent partitioned region in the inward direction (inward write count) by 1 (increment).

[0129] The refresh control unit 630 counts the number of times data is written to sectors located within a predetermined radius from the target sector (hereinafter also called "target sector") (hereinafter also called "nearby sector"). For example, the refresh control unit 630 counts the number of times data is written to nearby sectors located within a predetermined radius from the target sector (hereinafter also called "outer-direction near sector"). Additionally, for example, the refresh control unit 630 counts the number of times data is written to nearby sectors located within a predetermined radius from the target sector (hereinafter also called "outer-direction near sector"). Furthermore, sectors that cause bleeding, leakage magnetic fields, or other effects on the target area when data is written can be detected during the manufacturing stage, and these detected sectors can be designated as proximity sectors. Alternatively, sectors that cause bleeding, leakage magnetic fields, or other effects on the target area when data is written can be detected during the operation processing stage, and these detected sectors can be designated as proximity sectors.

[0130] When the refresh control unit 630 writes data to a nearby sector located within a predetermined radius from the target sector, it increases the number of writes to the nearby sector by a predetermined value (increment). For example, when the refresh control unit 630 writes data to a nearby sector located within a predetermined radius from the target sector, it increases the number of writes to the nearby sector by 1 (increment). When the refresh control unit 630 writes data to a sector located in the outer direction, it increases the number of writes to the sector located in the outer direction (outer direction write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to a sector located in the outer direction, it increases the number of writes to the sector located in the outer direction by 1 (increment). When the refresh control unit 630 writes data to a sector located in the inner direction, it increases the number of writes to the sector located in the inner direction by a predetermined value (increment). For example, when the refresh control unit 630 writes data to a sector located in the inner direction, it increases the number of writes to the sector located in the inner direction by 1 (increment).

[0131] The refresh control unit 630 counts the number of times data is written to adjacent sectors (hereinafter also referred to as adjacent sectors) in the radial direction of the target sector. For example, the refresh control unit 630 counts the number of times data is written to adjacent sectors (hereinafter also referred to as outer-direction adjacent sectors) in the outer direction of the target sector. Additionally, the refresh control unit 630 counts the number of times data is written to adjacent sectors (hereinafter also referred to as outer-direction adjacent sectors) in the inner direction of the target sector.

[0132] When the refresh control unit 630 writes data to an adjacent sector in the radial direction of the target sector, it increases the number of adjacent sector writes by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an adjacent sector in the radial direction of the target sector, it increases the number of adjacent sector writes by 1 (increment). When the refresh control unit 630 writes data to an outer adjacent sector, it increases the number of outer adjacent sector writes (outer direction write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an outer adjacent sector, it increases the number of outer adjacent sector writes (outer direction write count) by 1 (increment). When the refresh control unit 630 writes data to an inner adjacent sector, it increases the number of inner adjacent sector writes (inner direction write count) by a predetermined value (increment). For example, when the refresh control unit 630 writes data to an inner adjacent sector, it increases the number of inner adjacent sector writes (inner direction write count) by 1 (increment).

[0133] The refresh control unit 630 performs a process of rewriting data identical to data written to the object area back to the object area (hereinafter, this may also be referred to as rewriting, rewriting processing, refresh, or refresh processing), or a process of overwriting or rewriting data to the object area (hereinafter, this may also be referred to as overwriting processing, rewriting processing, rewriting, rewriting processing, refresh, or refresh processing). Hereinafter, the rewriting process, overwriting process, or rewriting process may be collectively referred to as rewriting, rewriting processing, refresh, or refresh processing. "Overwriting" includes "writing data on data written to a predetermined position in a predetermined area" and "writing data at the same position in the same area as data written to a predetermined position in a predetermined area."

[0134] The refresh control unit 630 has a threshold (hereinafter also referred to as the refresh threshold) for the number of write operations performed on a predetermined area. The refresh threshold is equivalent to the number of write operations performed on the area in the radial direction of the predetermined area when the data in the predetermined area is subjected to an ATI greater than a specific amount, such as the amount of data corruption. The refresh control unit 630 may also maintain the refresh threshold corresponding to the predetermined area as a table in a predetermined recording area, such as the system area 10b of disk 10, volatile memory 70, non-volatile memory 80, or buffer memory 90.

[0135] like Figure 7As shown, when the write processing parameters on a predetermined track are modified to suppress changes in evaluation metrics, edge writes to adjacent tracks may occur, potentially causing data degradation in a predetermined region of the track due to ATI (Automatic Data Interference) and suppressing data degradation in other regions of the track. Therefore, when the write processing parameters on a predetermined track are modified to suppress changes in evaluation metrics, it is preferable to set refresh thresholds for each region of the track by decreasing the refresh threshold for regions where data is easily degraded by ATI and increasing the refresh threshold for regions where data is less susceptible to ATI. In other words, when the write processing parameters on a predetermined track are modified to suppress changes in evaluation metrics, it is preferable to set refresh thresholds for each region of the track by decreasing the refresh threshold for regions where data is easily affected by ATI and increasing the refresh threshold for regions where data is less susceptible to ATI.

[0136] The refresh control unit 630 has refresh thresholds (hereinafter also referred to as partition region thresholds) for each partitioned region on a predetermined track. Based on changes in write processing parameters on the predetermined track, the refresh control unit 630 calculates the partition region thresholds by correcting a certain refresh threshold (hereinafter also referred to as a reference threshold) used for each partitioned region on the predetermined track. In other words, the refresh control unit 630 calculates the changes in partition region thresholds on the predetermined track, which are used to correct the reference thresholds on the predetermined track, and include multiple partition region thresholds corresponding to multiple partitioned regions.

[0137] For example, the refresh control unit 630 calculates each correction value (hereinafter also referred to as a threshold correction value) for each segmented region on the predetermined track based on the change in the TBG value, which corresponds to the change in the correction recording frequency proportional to the change in the correction recording density. In other words, the refresh control unit 630 calculates the change in the threshold correction value on the track that corrects for the change in the refresh threshold on the track based on the change in the TBG value on the predetermined track. The refresh control unit 630 calculates each segmented region threshold based on the reference threshold of each segmented region and the threshold correction value of each segmented region. In other words, the refresh control unit 630 calculates the change in the segmented region threshold on the track based on the change in the reference threshold and the threshold correction value on the predetermined track. For example, the refresh control unit 630 accumulates the threshold correction values ​​of each segmented region to the reference threshold of each segmented region on the predetermined track to calculate the segmented region threshold of each segmented region. In other words, the refresh control unit 630 accumulates the changes in the threshold correction value to the reference threshold on the predetermined track, and calculates the changes in the segmented region threshold on that track. Multiple segmented region thresholds on the predetermined track can also be different. A portion of the multiple segmented region thresholds on the predetermined track can also be the same.

[0138] When the refresh control unit 630 determines that the number of writes corresponding to the target region is greater than the refresh threshold corresponding to the target region, it performs refresh processing on the target region. Furthermore, when the refresh control unit 630 determines that the number of writes corresponding to the target region is greater than the refresh threshold corresponding to the target region, it performs refresh processing on the track including the target region (target track). After performing refresh processing on the target region, the refresh control unit 630 resets the number of writes corresponding to the target region, for example, to 0.

[0139] For example, if it is determined that the number of writes corresponding to an object partition region (e.g., the sum of outward and inward writes) is greater than the partition region threshold corresponding to that object partition region, the refresh control unit 630 reads the object partition region and performs a refresh process that rewrites the data in the object partition region to the same position in the object partition region. Furthermore, if it is determined that the number of writes corresponding to an object partition region is greater than the partition region threshold corresponding to that object partition region, the refresh control unit 630 may also read from the track containing the object partition region (object track) and perform a refresh process that rewrites the data in the track containing the object partition region to the same position in that track.

[0140] Figure 8 This is a schematic diagram illustrating an example of the variation of the TBG value of the predetermined track with respect to the circumferential position and the variation of the threshold correction value with respect to the circumferential position in this embodiment. Figure 8In the diagram, the vertical axis represents the TBG value and threshold correction value, and the horizontal axis represents the circumferential position. Figure 8 In the equation, the TBG value increases as it moves towards the front of the arrow that is more positive than the origin (=0), and decreases as it moves towards the front of the arrow that is more negative than the origin (=0). Figure 8 In the process, the threshold correction value increases as the arrow moves towards the front end of the arrow that is larger than the origin (=1), and decreases as the arrow moves towards the front end of the arrow that is smaller than the origin (=1). Figure 6 The circumferential position of the horizontal axis includes the start and end positions. Figure 8 The area at the circumference of the horizontal axis, from the start position to the end position, is divided into each subdivided region. Figure 8 The diagram shows the variation of the TBG value (hereinafter also referred to as the variation of the TBG value) on the predetermined track for the circumferential position, TBGL8, and the variation of the threshold correction value (hereinafter also referred to as the variation of the threshold correction value) on the predetermined track for the circumferential position, TCVL8.

[0141] exist Figure 8 In the example shown, the refresh control unit 630 calculates the change in threshold correction value TCVL8 for each division region of the predetermined track based on the change in TBGL8 of the TBG of the predetermined track. The refresh control unit 630 calculates the change in threshold correction value TCVL8 as follows: in division regions where the change in TBGL8 of TBG is smaller than the origin (=0), the change in threshold correction value TCVL8 is larger than the origin (=1); and in division regions where the change in TBGL8 of TBG is larger than the origin (=0), the change in threshold correction value TCVL8 is smaller than the origin (=1). For example, the refresh control unit 630 calculates the change in threshold correction value TCVL8 in a shape that is the inverse of the shape (waveform shape) of the change in TBGL8 of TBG. In other words, the refresh control unit 630 calculates the change in threshold correction value TCVL8 in a shape that is the inverse of the shape (waveform shape) of the write processing parameter, such as the change in recording density, corresponding to the change in TBGL8 of TBG. For example, the refresh control unit 630 calculates the change in threshold correction value TCVL8 in a way that is the shape of the change in correction write processing parameters corresponding to the change in TBG, such as the change in correction record density.

[0142] Figure 9 This is a schematic diagram illustrating an example of the variation of the segmentation threshold for a predetermined track in this embodiment. Figure 9 In the diagram, the vertical axis represents the refresh threshold, and the horizontal axis represents the circumferential position. Figure 9 In the middle, the refresh threshold increases as you move towards the front of the larger arrow and decreases as you move towards the front of the smaller arrow. Figure 9 The circumferential position of the horizontal axis includes the start and end positions. Figure 9The area at the circumference of the horizontal axis, from the start position to the end position, is divided into each subdivided region. Figure 9 The diagram shows the reference threshold CTVL9 on the predetermined track and the variation of the partition threshold for the partitioned region on the predetermined track (hereinafter, it may also be referred to as the variation of the partition threshold) DATL9.

[0143] exist Figure 9 In the example shown, the refresh control unit 630 will Figure 8 The variation of the threshold correction value, TCVL8, is accumulated to the reference threshold, CTVL9, to calculate the threshold for each segmented region, thus obtaining the variation of the segmented region threshold, DATL9. The variation of the segmented region threshold, DATL9, corresponds to the variation of the threshold correction value, TCVL8. In other words, the shape (e.g., waveform shape) of the variation of the segmented region threshold, DATL9, is almost identical to the shape of the variation of the threshold correction value, TCVL8. The shape of the variation of the segmented region threshold, DATL9, is almost the reverse of the shape of the variation of write processing parameters, such as the recording density, corresponding to the variation of the TBG, TBGL8. In segmented regions where the variation of TBG, TBGL8, is smaller than the origin (=0), the variation of the segmented region threshold, DATL9, is larger than the reference threshold, CTVL9; conversely, in segmented regions where the variation of TBG, TBGL8, is larger than the origin (=0), the variation of the segmented region threshold, DATL9, is smaller than the reference threshold, CTVL9. For example, the variation of the segmented region threshold, DATL9, is more susceptible to a smaller ATI segmented region when writing data to an adjacent track of a predetermined track, and less susceptible to a larger ATI segmented region when writing data to an adjacent track.

[0144] Figure 10 This is a schematic diagram illustrating an example of the division of a predetermined magnetic track. Figure 10 The diagram shows tracks CTRn-1, CTRn, and CTRn+1. Tracks CTRn-1, CTRn, and CTRn+1 correspond to... Figure 4 The magnetic tracks CTRn-1, CTRn, and CTRn+1 are shown. Figure 10 In the example shown, track CTRn-1 is divided into partition regions DA0(n-1), DA1(n-1), DA2(n-1), DA3(n-1), and DA4(n-1). These partition regions DA0(n-1), DA1(n-1), DA2(n-1), DA3(n-1), and DA4(n-1) are arranged consecutively in the described order. Figure 10 In the diagram, track CTRn is divided into regions DA0n, DA1n, DA2n, DA3n, and DA4n. These regions DA0n, DA1n, DA2n, DA3n, and DA4n are arranged consecutively in the order they are described. Figure 10In the diagram, track CTRn+1 is divided into regions DA0(n+1), DA1(n+1), DA2(n+1), DA3(n+1), and DA4(n+1). These regions are arranged consecutively in the order they are described. Figure 10 In the example shown, the regions DA0(n-1), DA0n, and DA0(n+1) are arranged consecutively in the inward direction, spaced apart, in the radial direction. Figure 10 In the example shown, in the radial direction, the regions DA1(n-1), DA1n, and DA1(n+1) are arranged consecutively in the inward direction, spaced apart by intervals, in the order described. Figure 10 In the example shown, in the radial direction, the regions DA2(n-1), DA2n, and DA2(n+1) are arranged consecutively in the inward direction, spaced apart by intervals, in the order described. Figure 10 In the example shown, in the radial direction, the regions DA3(n-1), DA3n, and DA3(n+1) are arranged consecutively at intervals in the inward direction in the recorded order. Figure 10 In the example shown, in the radial direction, the regions DA4(n-1), DA4n, and DA4(n+1) are arranged consecutively in the inward direction with intervals in the order described.

[0145] exist Figure 10 In the example shown, the refresh control unit 630 counts the number of writes to the partitioned regions DA0(n-1) and DA0(n+1). For example, when the refresh control unit 630 writes to the partitioned regions DA0(n-1) and DA0(n+1), it increments the number of writes to the partitioned region DA0n by 1.

[0146] exist Figure 10 In the example shown, the refresh control unit 630 counts the number of writes to the partitioned regions DA1(n-1) and DA1(n+1). For example, when the refresh control unit 630 writes to the partitioned regions DA1(n-1) and DA1(n+1), it increments the number of writes to the partitioned region DA1n by 1.

[0147] exist Figure 10 In the example shown, the refresh control unit 630 counts the number of writes to partitioned regions DA2(n-1) and DA2(n+1). For example, when partitioned regions DA2(n-1) and DA2(n+1) are written to, the refresh control unit 630 increments the number of writes to partitioned region DA2n by 1.

[0148] exist Figure 10 In the example shown, the refresh control unit 630 counts the number of writes to partitioned regions DA3(n-1) and DA3(n+1). For example, when partitioned regions DA3(n-1) and DA3(n+1) are written to, the refresh control unit 630 increments the number of writes to partitioned region DA3n by 1.

[0149] exist Figure 10 In the example shown, the refresh control unit 630 counts the number of writes to partitioned regions DA4(n-1) and DA4(n+1). For example, when partitioned regions DA4(n-1) and DA4(n+1) are written to, the refresh control unit 630 increments the number of writes to partitioned region DA4n by 1.

[0150] Figure 11 This is a schematic diagram illustrating an example of Table TB, which shows the number of writes and the threshold for dividing the region in this embodiment. Figure 11 In the table TB, track CTRn is included. Track CTRn corresponds to... Figure 10 . Figure 11 In this table, TB includes: partitioned regions DA0n, DA1n, DA2n, DA3n, and DA4n; write counts WC0n, WC1n, WC2n, WC3n, and WC4n; and partitioned region thresholds RHT0n, RHT1n, RHT2n, RHT3n, and RHT4n. Table TB can be recorded in predetermined recording areas, such as the system area 10b of disk 10, volatile memory 70, non-volatile memory 80, or buffer memory 90. Partitioned regions DA0n, DA1n, DA2n, DA3n, and DA4n correspond to tracks CTRn. Write counts WC0n correspond to partitioned region DA0n. Write counts WC1n correspond to partitioned region DA1n. Write counts WC2n correspond to partitioned region DA2n. Write counts WC3n correspond to partitioned region DA3n. Write counts WC4n correspond to partitioned region DA4n. Partitioned region threshold RHT0n corresponds to partitioned region DA0n. The region segmentation threshold RHT1n corresponds to the region segmentation DA1n. The region segmentation threshold RHT2n corresponds to the region segmentation DA2n. The region segmentation threshold RHT3n corresponds to the region segmentation DA3n. The region segmentation threshold RHT4n corresponds to the region segmentation DA4n.

[0151] exist Figure 11In the example shown, when the refresh control unit 630 writes to partitioned regions DA0(n-1) and DA0(n+1), it increases the write count WC0n corresponding to partitioned region DA0n by 1. If the refresh control unit 630 determines that the write count WC0n corresponding to partitioned region DA0n is greater than the partitioned region threshold RHT0n corresponding to partitioned region DA0n, it performs refresh processing on partitioned region DA0n. Furthermore, if the refresh control unit 630 determines that the write count WC0n corresponding to partitioned region DA0n is greater than the partitioned region threshold RHT0n corresponding to partitioned region DA0n, it performs refresh processing on track CTRn.

[0152] When the refresh control unit 630 writes to partitioned regions DA1(n-1) and DA1(n+1), it increments the write count WC1n corresponding to partitioned region DA1n by 1. If the refresh control unit 630 determines that the write count WC1n corresponding to partitioned region DA1n is greater than the partitioned region threshold RHT1n corresponding to partitioned region DA1n, it performs refresh processing on partitioned region DA1n. Furthermore, if the refresh control unit 630 determines that the write count WC1n corresponding to partitioned region DA1n is greater than the partitioned region threshold RHT1n corresponding to partitioned region DA1n, it performs refresh processing on track CTRn.

[0153] When the refresh control unit 630 writes to partitioned regions DA2(n-1) and DA2(n+1), it increments the write count WC2n corresponding to partitioned region DA2n by 1. If the refresh control unit 630 determines that the write count WC2n corresponding to partitioned region DA2n is greater than the partitioned region threshold RHT2n corresponding to partitioned region DA2n, it performs refresh processing on partitioned region DA2n. Furthermore, if the refresh control unit 630 determines that the write count WC2n corresponding to partitioned region DA2n is greater than the partitioned region threshold RHT2n corresponding to partitioned region DA2n, it performs refresh processing on track CTRn.

[0154] When the refresh control unit 630 writes to partitioned regions DA3(n-1) and DA3(n+1), it increments the write count WC3n corresponding to partitioned region DA3n by 1. If the refresh control unit 630 determines that the write count WC3n corresponding to partitioned region DA3n is greater than the partitioned region threshold RHT3n corresponding to partitioned region DA3n, it performs refresh processing on partitioned region DA3n. Furthermore, if the refresh control unit 630 determines that the write count WC3n corresponding to partitioned region DA3n is greater than the partitioned region threshold RHT3n corresponding to partitioned region DA3n, it performs refresh processing on track CTRn.

[0155] When the refresh control unit 630 writes to partitioned regions DA4(n-1) and DA4(n+1), it increments the write count WC4n corresponding to partitioned region DA4n by 1. If the refresh control unit 630 determines that the write count WC4n corresponding to partitioned region DA4n is greater than the partitioned region threshold RHT4n corresponding to partitioned region DA4n, it performs refresh processing on partitioned region DA4n. Furthermore, if the refresh control unit 630 determines that the write count WC4n corresponding to partitioned region DA4n is greater than the partitioned region threshold RHT4n corresponding to partitioned region DA4n, it performs refresh processing on track CTRn.

[0156] Figure 12 This is a flowchart illustrating an example of the refresh threshold setting method in this embodiment.

[0157] On a predetermined track, the MPU60 sets the write processing parameters to the baseline write processing parameters (B1201) and measures the variation of the measured evaluation index on that track (B1202). Based on the measured variation of the measured evaluation index on the predetermined track, the MPU60 calculates the variation of the write processing parameter correction amount on that track to adjust the variation of the measured evaluation index on that track to uniformity or suppression (B1203). Based on the variation of the baseline write processing parameters and the variation of the write processing parameter correction amount, the MPU60 calculates the variation of the corrected write processing parameters for the predetermined track (B1204). Based on the variation of the corrected write processing parameters for the predetermined track, the MPU60 calculates the variation of the threshold correction value on that track by reducing the refresh threshold of areas of the predetermined track that are susceptible to ATI, etc., and increasing the refresh threshold of areas of the track that are not susceptible to ATI, etc. (B1205). In other words, the MPU60 calculates the threshold correction value for each segment of the track based on the changes in the correction write processing parameters of the predetermined track, thereby reducing the refresh threshold of areas of the predetermined track that are susceptible to ATI and increasing the refresh threshold of areas of the track that are not susceptible to ATI and the like. Based on the changes in the threshold correction values ​​on the predetermined track, the MPU60 sets the threshold change for each segment of the track (B1206) and ends the processing. In other words, the MPU60 sets the threshold for each segment of the track based on the threshold correction values ​​for each segment.

[0158] Figure 13 This is a schematic diagram illustrating an example of the refresh processing method of this embodiment.

[0159] MPU60 writes data to adjacent partition regions of the target track in the radial direction that are adjacent to the target partition region (B1301), and counts the number of writes to the target partition region (B1302). MPU60 determines whether the number of writes to the target partition region is greater than or less than the partition region threshold (B1303). If it is determined that the number of writes to the target partition region is less than the partition region threshold (B1303 "No"), MPU60 ends the processing. If it is determined that the number of writes to the target partition region is greater than the partition region threshold (B1303 "Yes"), MPU60 performs refresh processing on the target partition region (B1304) and ends the processing. Alternatively, if it is determined that the number of writes to the target partition region is greater than the partition region threshold, MPU60 may also perform refresh processing on the target track.

[0160] According to this embodiment, the disk drive 1 sets the write processing parameters as reference write processing parameters on a predetermined track and measures the variation of the measured evaluation index on that track. Based on the measured variation of the measured evaluation index on the predetermined track, the disk drive 1 calculates a change in the write processing parameter correction amount on that track to adjust the variation of the measured evaluation index on that track to be uniform or suppressed. Based on the variation of the reference write processing parameters and the change in the write processing parameter correction amount, the disk drive 1 calculates a change in the corrected write processing parameters for the predetermined track. Based on the change in the corrected write processing parameters of the predetermined track, the disk drive 1 calculates a change in the threshold correction value on that track by reducing the refresh threshold of areas of the predetermined track that are easily affected by ATI, etc., and increasing the refresh threshold of areas of the track that are not easily affected by ATI, etc. Based on the change in the threshold correction value on the predetermined track, the disk drive 1 sets a change in the segmentation threshold of that track. Therefore, the disk drive 1 can improve performance and data reliability.

[0161] While several embodiments have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in a wide variety of other ways, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their variations are included in the scope and spirit of the invention, and are also included in the scope of the invention as described in the claims and their equivalents.

Claims

1. A disk drive, comprising: The disk has a first track; A head, having a heater, for writing data to the disk and reading data from the disk; and The controller sets the variation of parameters associated with write processing to the disk within one cycle of the first track, so as to suppress the variation of evaluation indicators corresponding to write / read processing characteristics within one cycle of the first track. The controller, based on the changes in the parameters, sets the refresh threshold for performing rewrite processing on the first track within one week. The changes in the refresh threshold include: Multiple refresh thresholds corresponding to the multiple division regions obtained by dividing the first track, The change in the refresh threshold is the inverse of the change in the shape set by the controller and the change in the shape of the parameter.

2. The disk drive according to claim 1, The controller sets the refresh threshold to vary such that the first partition region in the plurality of partitioned regions becomes smaller and the second partition region in the plurality of partitioned regions becomes larger. The first partition region is a region that is easily affected by the leakage flux of the head when data is written to an adjacent track that is adjacent to the first track in the radial direction of the disk. The second partition region is a region that is less affected by the leakage flux of the head when data is written to the adjacent track.

3. The disk drive according to claim 2, The change in the evaluation metric is the change in bit error rate.

4. The disk drive according to claim 3, The change in the parameter is a change in the recording density.

5. The disk drive according to claim 3, The change in the parameter is a change in the recorded current.

6. The disk drive according to claim 4, The change in the parameter is a change in the set value of the heater.

7. The disk drive according to claim 4, The change in the parameter is a change in the data transmission speed.

8. The disk drive according to claim 4, The change in the parameter is a change in the recording frequency.

9. The disk drive according to claim 1, The controller rewrites the data in the first partition region if it determines that the first write count of the data written to the adjacent partition region of the first partition region in the radial direction of the disk is greater than the first refresh threshold in the change of the refresh threshold corresponding to the first partition region.

10. The disk drive according to claim 1, The controller rewrites the data on the first track if it determines that the first write count of the data written to the adjacent partition region of the first partition region in the radial direction of the disk is greater than the first refresh threshold in the change of the refresh threshold corresponding to the first partition region.

11. A method for setting a refresh threshold, applicable to a disk device comprising: a disk having a first track; and a head having a heater, for writing data to the disk and reading data from the disk, the method for setting the refresh threshold comprising: The parameters associated with write processing to the disk are set to vary within one week of the first track, so as to suppress variations in evaluation metrics corresponding to write / read processing characteristics within one week of the first track. Based on the changes in the aforementioned parameters, the refresh threshold for performing rewrite processing within one week is set to change for the first track. The variation of the refresh threshold includes: multiple refresh thresholds corresponding to the multiple division regions obtained by dividing the first track. The refresh threshold is changed by setting the shape and the shape of the change in the parameter.

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