Magnetic disk drive

Abstract

The present invention provides a magnetic disk device that can predict, in conjunction with seek operations, whether error correction on the data track of the disk has reached its limit. [Solution] The magnetic disk device comprises a disk DK, a head HD, a read processing unit 63, a write processing unit 62, an error correction unit 64, an adjustment unit 65, a correction limit prediction unit 66, and a determination unit 67. During the first write period, the adjustment unit 65 derives a first predicted excess amount that varies according to the distance the read head RHD seeks, and also derives a predicted upper threshold, and the correction limit prediction unit 66 calculates a first cumulative predicted excess amount. If the determination unit 67 determines that the first cumulative predicted excess amount is less than or equal to the predicted upper threshold, it instructs the write processing unit 62 to continue the write process. If the determination unit 67 determines that the first cumulative predicted excess amount exceeds the predicted upper threshold, it instructs the write processing unit 62 to pause the write process.

Description

Technical Field

[0001] Embodiments of the present invention relate to a magnetic disk drive.

Background Art

[0002] As magnetic disk drives, there are known a magnetic disk drive of a Conventional Magnetic Recording (CMR) format (or, a conventional recording format) that writes a plurality of tracks at intervals in the radial direction of a disk, a magnetic disk drive of a Shingled Magnetic Recording (SMR) format that overlays and writes a plurality of tracks in the radial direction of a disk, and a magnetic disk drive of a hybrid recording format that selects and executes the conventional recording format and the shingled recording format.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Summary of the Invention

Problems to be Solved by the Invention

[0004] The present embodiment provides a magnetic disk drive capable of predicting whether error correction for a data track of a disk has reached a limit in association with a seek operation.

Means for Solving the Problems

[0005] A magnetic disk device according to one embodiment is described as follows: A disk having a first data track and a second data track adjacent to each other on a recording layer, wherein the first data track and the second data track each include a plurality of target sectors on which data is to be written, and the first data track is located in a first direction parallel to the radial direction of the disk with respect to the second data track, A head having a write head for writing data to the recording layer and a read head for reading data from the recording layer, A read processing unit capable of performing a seek operation to seek the read head, A write processing unit capable of performing a write operation to write data to the recording layer, An error correction unit that performs error correction on the data of one or more corrupted target sectors of the first data track that are determined to have corrupted data, Adjustment section, Correction limit prediction unit, It comprises a determination unit, During the first write period, which is the period after the write processing unit has performed the write processing on the plurality of target sectors of the first data track and during the period in which the write processing is performed on the plurality of target sectors of the second data track, The read processing unit performs a first seek process to seek the read head, moves the read head by a first distance, and positions the write head opposite the second data track. The adjustment unit is, This is a first predicted excess amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction during the first light period, and the first predicted excess amount is derived which varies depending on the distance the read head seeks. This is a predictive upper limit threshold that indicates the limit of the range in which the error correction can be performed on the first data track, and the predictive upper limit threshold, which is a constant, is derived. The correction limit prediction unit measures the actual excess amount by which the position of the light head extends beyond the reference radius position in the first direction each time data is written to the target sector of the second data track, updates the cumulative actual excess amount which is the sum of the actual excess amounts, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount. The unit that makes the determination said, If it is determined that the first cumulative excess amount is less than or equal to the prediction upper threshold, the write processing unit is instructed to continue the write processing for the second data track. If it is determined that the first cumulative excess amount exceeds the prediction upper threshold, the write processing unit is instructed to pause the write processing for the second data track.

[0006] Furthermore, the magnetic disk device according to one embodiment is A disk having a first data track and a second data track adjacent to each other on a recording layer, wherein the first data track and the second data track each include a plurality of target sectors on which data is to be written, and the first data track is located in a first direction parallel to the radial direction of the disk with respect to the second data track, A head having a write head for writing data to the recording layer and a read head for reading data from the recording layer, A read processing unit capable of performing a seek operation to seek the read head, A write processing unit capable of performing a write operation to write data to the recording layer, An error correction unit that performs error correction on the data of one or more corrupted target sectors of the first data track that are determined to have corrupted data, Adjustment section, Correction limit prediction unit, It comprises a determination unit, During the first write period, which is the period after the write processing unit has performed the write processing on the plurality of target sectors of the first data track and during the period in which the write processing is performed on the plurality of target sectors of the second data track, The read processing unit performs a first seek process to seek the read head, moves the read head by a first distance, and positions the write head opposite the second data track. The adjustment unit is, This is a first predicted excess amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction during the first light period, and the first predicted excess amount is derived which varies depending on the distance the read head seeks, and, A prediction upper limit threshold that indicates the limit of the range in which the error correction can be performed on the first data track, wherein the prediction upper limit threshold has a smaller value as each prediction excess amount, including the first prediction excess amount, increases, and the prediction upper limit threshold, which is a variable, is derived. The correction limit prediction unit measures the actual excess amount by which the position of the light head extends beyond the reference radius position in the first direction each time data is written to the target sector of the second data track, updates the cumulative actual excess amount which is the sum of the actual excess amounts, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount. The unit that makes the determination said, If it is determined that the first cumulative excess amount is less than or equal to the prediction upper threshold, the write processing unit is instructed to continue the write processing for the second data track. If it is determined that the first cumulative excess amount exceeds the prediction upper threshold, the write processing unit is instructed to pause the write processing for the second data track. [Brief explanation of the drawing]

[0007] [Figure 1] Figure 1 is a block diagram showing the configuration of a magnetic disk device according to one embodiment. [Figure 2]FIG. 2 is a perspective view showing a part of the magnetic disk device, and shows a plurality of disks and a plurality of heads. [Figure 3] FIG. 3 is a schematic view showing an example of the arrangement of a plurality of servo areas and a plurality of data areas on one disk according to the above embodiment. [Figure 4] FIG. 4 is a schematic diagram showing three tracks of a user data area where the tiled recording process of the disk shown in FIG. 3 is performed, and a write head. [Figure 5] FIG. 5 is a schematic diagram showing three tracks of a media cache where the normal recording process of the disk shown in FIG. 3 is performed, and a write head. [Figure 6] FIG. 6 is a schematic diagram showing an example of the write process of data on a disk. [Figure 7] FIG. 7 is a schematic diagram showing two bands and one guard band in the user data area shown in FIG. 6. [Figure 8] FIG. 8 is a schematic diagram showing three sectors in one track of the band shown in FIG. 6. [Figure 9] FIG. 9 is a schematic diagram showing two bands and one guard band shown in FIG. 7, and is a diagram for explaining a plurality of target sectors and a plurality of unused sectors. [Figure 10] FIG. 10 is a schematic diagram showing an example of a first track and a second track when it is assumed that the magnetic disk device does not have a function of performing track unit error correction on track data, and is a diagram for explaining the write process for the first track and the second track. It is a diagram for explaining a state in which the write process for the second track is continued until the sector unit error correction for the first track reaches the limit, and is a diagram showing, in a graph, the change in BER for the first track and the change in BER for the positioning error, respectively. [Figure 11]Figure 11 is a schematic diagram showing an example of the first and second tracks, assuming that the magnetic disk device does not have the function to perform track-level error correction on the track data. It is a diagram to explain the write process for the first and second tracks. It is a diagram to explain the state in which the write process for the second track is terminated when the judgment value is set to a write-off track slice smaller than the track margin (stricter) and it is detected that the positioning error exceeds the reference radius position. It is a diagram that shows the change in BER for the first track and the change in BER for the positioning error in graph form. [Figure 12] Figure 12 is a schematic diagram showing an example of the first and second tracks of the magnetic disk device described above, which has a function to perform track-level error correction on the data of the track. It is a diagram for explaining the write process for the first and second tracks. It is a diagram for explaining a state in which the judgment value is set to a write-off track slice that is larger (looser) than the track margin, and the write process for the second track is continued until the track-level error correction for the first track reaches its limit. The diagram shows the change in BER for the first track and the change in BER for positioning error, respectively, in graph form. [Figure 13] Figure 13 is a table showing the presence or absence of track ECC in the first to third methods of the first and second light operations, the function name for controlling the DOL, the processing when the positioning error exceeds the reference radius position, the setting of the predicted upper threshold, and the setting of the predicted excess amount. [Figure 14] Figure 14 is a bar graph showing the change in the predicted excess amount with respect to the seek distance of the magnetic disk device described above. [Figure 15] Figure 15 shows the changes in positioning error, cumulative excess amount, and cumulative predicted excess amount when the second track is subjected to the second and third methods of the second light operation described above, and is a diagram showing the case when the predicted upper threshold is constant. [Figure 16]Figure 16 shows the changes in positioning error, cumulative excess amount, and cumulative predicted excess amount when the second track is written using the second and third methods of the second writing operation described above, and illustrates the case where the predicted upper threshold is a variable. [Figure 17] Figure 17 is a bar graph showing the number of PTS occurrences (occurrence rate) when the magnetic disk drive employs the first method of second write operation and the second method of second write operation. [Figure 18] Figure 18 is a flowchart showing a write processing method for the nth target sector of the second track according to the above embodiment, and is a diagram showing the case when the magnetic disk device employs the first write operation during the first write period. [Figure 19] Figure 19 is a flowchart showing the write processing method for the nth target sector of the second track according to the above embodiment, and is a diagram showing the case when the magnetic disk device adopts the second method of the second write operation during the first write period. [Figure 20] Figure 20 is a flowchart showing the light processing method described above, following Figure 19. [Figure 21] Figure 21 is a flowchart showing the write processing method for the nth target sector of the second track according to the above embodiment, and is a diagram showing the case when the magnetic disk device adopts the third method of the second write operation during the first write period and the second write period. [Figure 22] Figure 22 is a flowchart showing the light processing method described above, following Figure 21. [Figure 23] Figure 23 is a flowchart showing the light processing method described above, following Figure 22. [Modes for carrying out the invention]

[0008] Hereinafter, a magnetic disk device 1 according to one embodiment will be described in detail with reference to the drawings. First, the configuration of the magnetic disk device 1 will be described. Figure 1 is a block diagram showing the configuration of the magnetic disk device 1 according to this embodiment. In this embodiment, the magnetic disk device 1 is a hybrid recording type magnetic disk device that can select and perform both normal recording and tile recording. However, the technology described later may be applied to a tile recording type magnetic disk device or a normal recording type magnetic disk device.

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

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

[0011] The head stack assembly 22 can move the head HD mounted on the arm 30 to a target position on the disk DK, i.e., seek, by driving the voice coil motor (hereinafter referred to as VCM) 24. The VCM 24 functions as an actuator. Disk DK has two areas allocated to its writable data: a user data area U, which is accessible to users, and a system area S, which is used to write information necessary for system management.

[0012] The head HD records and plays back information to and from the disk DK. The head HD consists of a slider as its main body, and includes a write head WHD and a read head RHD mounted on the slider. The write head WHD writes data to the recording layer of the disk DK. The read head RHD reads data from the data track of the recording layer of the disk DK.

[0013] Sometimes the "center of the head HD" is referred to as "head HD," the "center of the light head WHD" as "light head WHD," and the "center of the read head RHD" as "read head RHD." Sometimes the "center of the light head WHD" is simply referred to as "head HD," and sometimes the "center of the read head RHD" is simply referred to as "head HD."

[0014] The driver IC 120 controls the driving of the SPM20 and VCM24 according to the control of the system controller 110 (specifically, the MPU 60, which will be described later). The SPM20 supports and rotates multiple disk DKs.

[0015] The head amplifier IC 130 includes a read amplifier and a write driver. The read amplifier amplifies the read signal read from the disk DK and outputs it to the system controller 110 (specifically, the read / write (R / W) channel 140, which will be described later). The write driver outputs a write current to the head HD corresponding to the signal output from the R / W channel 140.

[0016] The volatile memory 70 is a semiconductor memory in which the data stored is lost when the power supply is cut off. The volatile memory 70 stores data necessary for processing in each part of the magnetic disk device 1. The volatile memory 70 is a random access memory (RAM). For example, the volatile memory 70 is a DRAM (Dynamic Random Access Memory). However, the volatile memory 70 may also be an SDRAM (Synchronous Dynamic Random Access Memory).

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

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

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

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

[0021] The HDC150 controls data transfer between the host 100 and the R / W channel 140 in response to instructions from the MPU60. The HDC150 is electrically connected to, for example, the R / W channel 140, the MPU60, the volatile memory 70, the buffer memory 80, the non-volatile memory 90, etc.

[0022] The HDC150 has a gate generation unit. The gate generation unit generates various gates, such as write gates, read gates, and servo gates, in response to commands from the host 100, instructions from the MPU 60, etc., and outputs them to the R / W channel 140, for example, the gate detection unit. Hereinafter, "raising a predetermined gate" may be referred to as "asserting a predetermined gate." Similarly, "lowering a predetermined gate" may be referred to as "negating a predetermined gate." "Asserting a predetermined gate" and "negating a predetermined gate" may also include the meaning of "generating a predetermined gate." The gate generation unit may be included in the R / W channel 140 or the MPU 60.

[0023] The R / W channel 140 has a gate detection unit. The gate detection unit detects whether various gates, such as a light gate, read gate, or servo gate, are in an asserted or negated state. For example, the gate detection unit executes the write process when it detects that the write gate is asserted, and pauses (stops) the write process when it detects that the write gate is negated. In addition, the gate detection unit executes read processing when it detects that a read gate is asserted, and stops read processing when it detects that a read gate is negated. The gate detection unit executes servo read processing when it detects that a servo gate is asserted, and stops servo read processing when it detects that a servo gate is negated. The gate detection unit may be located within the HDC150 or MPU60.

[0024] The MPU60 is a control unit that controls various parts of the magnetic disk drive 1 and is the main controller. The MPU60 controls the VCM24 via the driver IC120 and performs servo control to position the head HD. The MPU60 controls the write operation of data to the disk DK and selects the storage location for the write data transferred from the host 100. The MPU60 also controls the read operation of data from the disk DK and controls the processing of the read data transferred from the disk DK to the host 100. The MPU60 is connected to various parts of the magnetic disk drive 1. For example, the MPU60 is electrically connected to the driver IC120, R / W channel 140, HDC150, etc.

[0025] The MPU60 includes a read / write processing unit 61, an error correction unit 64, an adjustment unit 65, a correction limit prediction unit 66, a decision unit 67, a management unit 68, and the like. The MPU60 executes the processing of each of these units, such as the read / write processing unit 61, the error correction unit 64, the adjustment unit 65, the correction limit prediction unit 66, the decision unit 67, and the management unit 68, on the firmware. The MPU60 may also include each of these units as a circuit.

[0026] The read / write processing unit 61 includes a write processing unit 62 and a read processing unit 63. According to commands from the host 100, the write processing unit 62 controls the data writing process, and the read processing unit 63 controls the data reading process, causing the read head RHD to read data from the disk DK. The read processing unit 63 is capable of performing a seek process to move the read head RHD. The write processing unit 62 is capable of performing write operations to write data to the recording layer of the disk DK. The read / write processing unit 61 controls the VCM24 via the driver IC 120 to position the head HD at a target position (a predetermined radius position) on the disk DK and performs read or write operations.

[0027] Figure 2 is a perspective view showing a part of the magnetic disk drive 1, and shows multiple disks DK and multiple heads HD. As shown in Figure 2, the direction in which the disk DK rotates in the circumferential direction is called the rotation direction d3. In the example shown in Figure 2, the rotation direction d3 is shown as counterclockwise, but it may also be in the opposite direction (clockwise). Furthermore, the direction of travel d2 of the head HD relative to the disk DK is opposite to the rotation direction d3. The direction of travel d2 is the direction in which the head HD sequentially writes and reads data relative to the disk DK in the circumferential direction, that is, the direction in which the head HD moves relative to the disk DK in the circumferential direction.

[0028] The magnetic disk drive 1 comprises i disks, numbered DK1 to DKi, and j heads, numbered HD1 to HDj. In this embodiment, the number of heads HD is twice the number of disks DK (j = 2 × i). Disks DK1 through DKi are mounted coaxially and stacked with a gap between them. Disks DK1 through DKi have the same diameter. Here, terms such as “same,” “identical,” “matching,” and “equivalent” include not only the meaning of being exactly the same, but also the meaning of being different to the extent that they can be considered substantially the same. Note that the diameters of disks DK1 through DKi may differ from each other.

[0029] Each disk DK has recording layers L on both sides. For example, disk DK1 has a first recording layer La1 and a second recording layer Lb1 on the opposite side of the first recording layer La1. Disk DK2 has a first recording layer La2 and a second recording layer Lb2 on the opposite side of the first recording layer La2. Disk DKi has a first recording layer Lai and a second recording layer Lbi on the opposite side of the first recording layer Lai. Each first recording layer La may also be referred to as the front or recording surface. Each second recording layer Lb may also be referred to as the back or recording surface. However, each first recording layer La is sometimes referred to as the back surface. In this case, each second recording layer Lb is sometimes referred to as the front surface.

[0030] Each recording layer L has a user data area U and a system area S. The first recording layer La1 has a user data area Ua1 and a system area Sa1. The second recording layer Lb1 has a user data area Ub1 and a system area Sb1. The first recording layer La2 has a user data area Ua2 and a system area Sa2. The second recording layer Lb2 has a user data area Ub2 and a system area Sb2. The first recording layer Lai has a user data area Uai and a system area Sai. The second recording layer Lbi has a user data area Ubi and a system area Sbi.

[0031] Within the user data area Ua1 (first recording layer La1), the track enclosed by the double dashed lines in the diagram is designated as track Ta1. Within the user data area Ub1 (second recording layer Lb1), the track located on the opposite side of track Ta1 is designated as track Tb1. In the user data area Ua2 (first recording layer La2), the track enclosed by the double dashed lines in the diagram is designated as track Tc1. In the user data area Ub2 (second recording layer Lb2), the track located on the opposite side of track Tc1 is designated as track Td1. Within the user data area Uai (first recording layer Lai), the track enclosed by the double dashed lines in the diagram is designated as track Te1. Within the user data area Ubi (second recording layer Lbi), the track located on the opposite side of track Te1 is designated as track Tf1. In this embodiment, tracks Ta1, Tb1, Tc1, Td1, Te1, and Tf1 are located in the same cylinder.

[0032] The head HD faces the disk DK. In this embodiment, one head HD faces each recording layer L of the disk DK. For example, head HD1 faces the first recording layer La1 of disk DK1, writes data to the first recording layer La1, and reads data from the first recording layer La1. Head HD2 faces the second recording layer Lb1 of disk DK1, writes data to the second recording layer Lb1, and reads data from the second recording layer Lb1.

[0033] Head HD3 faces the first recording layer La2 of disk DK2, writes data to the first recording layer La2, and reads data from the first recording layer La2. Head HD4 faces the second recording layer Lb2 of disk DK2, writes data to the second recording layer Lb2, and reads data from the second recording layer Lb2. Head HDj-1 faces the first recording layer Lai of disk DKi, writes data to the first recording layer Lai, and reads data from the first recording layer Lai. Head HDj faces the second recording layer Lbi of disk DKi, writes data to the second recording layer Lbi, and reads data from the second recording layer Lbi.

[0034] Figure 3 is a schematic diagram showing an example of the arrangement of multiple servo regions SV and multiple data regions DTR on a single disk DK according to this embodiment. As shown in Figure 3, in the radial direction d1 of the disk DK, the direction toward the outer circumference of the disk DK is referred to as the outward direction (outside), and the direction opposite to the outward direction is referred to as the inward direction (inside). In Figure 3, the user data area U is divided into an inner circumference area IR located in the inward direction, an outer circumference area OR located in the outward direction, and a middle circumference area MR located between the inner circumference area IR and the outer circumference area OR.

[0035] The disk DK has multiple servo regions SV and multiple data regions DTR. The multiple servo regions SV may, for example, extend radially in the radial direction of the disk DK and be discretely arranged at predetermined intervals in the circumferential direction. The multiple servo regions SV may, for example, extend linearly from the inner circumference to the outer circumference and be discretely arranged at predetermined intervals in the circumferential direction. The multiple servo regions SV may, for example, extend spirally from the inner circumference to the outer circumference and be discretely arranged at predetermined intervals in the circumferential direction. Alternatively, the multiple servo regions SV may, for example, be arranged in an island-like manner in the radial direction and discretely arranged at predetermined intervals in the circumferential direction.

[0036] Hereafter, a single servo region SV on a given track may be referred to as a "servo sector." Furthermore, a "servo region SV" may also be referred to as a "servo sector SV." A servo sector contains servo data. Hereafter, the "arrangement of several servo data that constitute a servo sector" may be referred to as a "servo pattern." Furthermore, the "servo data written to a servo sector" may also be referred to as a "servo sector."

[0037] Multiple data areas DTR are each positioned between multiple servo areas SV. For example, a data area DTR corresponds to the area between two consecutive servo areas SV in the circumferential direction. Hereinafter, one data area DTR in a given track may be referred to as a "data sector." Note that a "data area DTR" may also be referred to as a "data sector DTR." A data sector contains user data. Note that "user data written to a data sector" may also be referred to as a "data sector." A "data sector" may also be referred to as "user data." Furthermore, a "pattern composed of several data" may also be referred to as a "data pattern." In the example shown in Figure 3, the data pattern of a given track consists of multiple servo data (servo sectors) and multiple user data (data sectors).

[0038] The servo region SV has multiple zone servo regions ZSV, etc. In addition to the zone servo regions ZSV, the servo region SV may also include a region containing a gap (the circumferential positional difference between two zone servo regions), a region containing servo data, and a data region DTR, etc. The multiple zone servo regions ZSV are discretely arranged along the radial direction d1. Each of the multiple zone servo regions ZSV extends radially along d1.

[0039] A single zone servo area (servo area) ZSV on a given track may be referred to as a "zone servo sector" or "servo sector." Furthermore, a "zone servo area (servo area) ZSV" may also be referred to as a "zone servo sector ZSV" or "servo sector ZSV." The "servo data written to a zone servo sector" may also be referred to as a "zone servo sector" or "servo sector." Hereafter, the "arrangement of several servo data that constitute a zone servo sector" may be referred to as a "zone servo pattern" or "servo pattern." Hereafter, a single servo area SV on a given track may also be referred to as a "zone pattern sector."

[0040] Note that the “servo area SV” may also be referred to as the “zone pattern sector.” The “at least one piece of data written to the zone pattern sector” may also be referred to as the “zone pattern sector.” A zone pattern sector includes at least one zone servo sector. Hereinafter, the “data pattern of the zone pattern sector” may also be referred to as the “zone data pattern.”

[0041] In the example shown in Figure 3, the servo region SV has zone servo regions ZSV0, ZSV1, and ZSV2. The zone servo regions ZSV0, ZSV1, and ZSV2 are arranged in a staggered pattern in the radial direction. The zone servo regions ZSV0, ZSV1, and ZSV2 may also be arranged in a stepped pattern in the radial direction.

[0042] Zone servo region ZSV2 is located on the inner circumference side of zone servo region ZSV1. Zone servo region ZSV0 is located on the outer circumference side of zone servo region ZSV1. For example, zone servo region ZSV2 is arranged from the inner circumference region IR to the middle circumference region MR, zone servo region ZSV1 is arranged from the inner circumference region IR to the outer circumference region OR, and zone servo region ZSV0 is arranged from the middle circumference region MR to the outer circumference region OR. Hereinafter, in a given servo region SV, a predetermined radial region in which multiple zone servo regions ZSV are arranged in the circumferential direction may be referred to as a zone servo boundary region, a double servo region, or a double zone servo region ZB.

[0043] In the example shown in Figure 3, the main servo region SVO and the secondary servo region SVE are arranged alternately with spacing in the circumferential direction. For example, one secondary servo region SVE is placed between two main servo regions SVO that are spaced apart and arranged consecutively in the circumferential direction. In other words, one secondary servo region SVE is placed between two main servo regions SVO that are spaced apart and arranged consecutively in the circumferential direction. For example, if all servo regions SV of disk DK are assigned sequential numbers, the main servo region SVO corresponds to the odd-numbered servo region SV, and the secondary servo region SVE corresponds to the even-numbered servo region SV. Note that two or more secondary servo regions SVE may be placed between two main servo regions SVO that are spaced apart and arranged consecutively in the circumferential direction.

[0044] The main servo region SVO and the secondary servo region SVE may consist, for example, only of a servo region that reads and demodulates servo data overall (hereinafter sometimes referred to as the normal servo region). Hereinafter, "reading and demodulating servo data" may be referred to as "servo reading". The main servo region SVO and the secondary servo region SVE may consist, for example, of a normal servo region and a servo region that servo reads a range of servo data in the circumferential direction that is smaller than the range of servo data read in the normal servo region (hereinafter sometimes referred to as the short servo region).

[0045] The media cache M is allocated to disk DK. However, the media cache M does not necessarily have to be located on disk DK. By using the multiple servo data mentioned above, it is possible to derive, for example, the positioning error of the head HD (e.g., the light head WHD).

[0046] In this embodiment, the case where the disk DK has 3 zones was described as an example, but the number of zones in the disk DK can be changed in various ways. The number of zones in the disk DK may be 30 to 40. Furthermore, each zone has multiple bands. For example, each zone may have several hundred bands.

[0047] Figure 4 is a schematic diagram showing the three tracks STR of the user data area U where the tile recording process of disk DK shown in Figure 3 takes place, and the write head WHD. The user data area U is a tile recording area. Within the user data area U, sequential writing of data on a band-by-band basis is permitted; in other words, tile recording is permitted.

[0048] As shown in Figure 4, the write head WHD can sequentially write data to disk DK in the direction of travel d2. The read head RHD shown in Figure 3 can also sequentially read data written to disk DK in the direction of travel d2.

[0049] In a direction parallel to the radial direction d1, the direction in which multiple data tracks, or multiple track STRs, are recorded consecutively, that is, the direction in which the next track STR to be written is superimposed on the track STR that was written one step earlier in the radial direction d1, is called the overwriting direction or recording progress direction. In band BAe shown in Figure 4, the overwriting direction d5 is inward, but the overwriting direction may also be outward. For example, the overlay direction applied to multiple bands BA (multiple zones Z) located on the outer circumference side of a specific radial position may be opposite to the overlay direction applied to multiple bands BA (multiple zones Z) located on the inner circumference side of the specific radial position.

[0050] Band BAe has multiple tracks STR, including tracks STRe, STRe+1, and STRe+2. Tracks STRe, STRe+1, and STRe+2 are written sequentially in the writing direction d5 in the order they are described. Of tracks STRe, STRe+1, and STRe+2, track STRe is the track to which data is written first, and track STRe+2 is the track to which data is written last.

[0051] Track STRe has a track center STCe at the center of radial d1 when no other tracks are overlapping it. Track STRe+1 has a track center STCe+1 at the center of radial d1 when no other tracks are overlapping it. Track STRe+2 has a track center STCe+2 at the center of radial d1 when no other tracks are overlapping it.

[0052] In the example shown in Figure 4, tracks STRe, STRe+1, and STRe+2 are lit with a pitch (tile recording track pitch) STP. The track center STCe of track STRe and the track center STCe+1 of track STRe+1 are separated by a pitch STP in the radial direction d1. The track center STCe+1 of track STRe+1 and the track center STCe+2 of track STRe+2 are separated by a pitch STP in the radial direction d1. Tracks STRe through STRe+2 may be lit with different pitches.

[0053] The radial width d1 of the area within track STRe where track STRe+1 is not superimposed is the same as the radial width d1 of the area within track STRe+1 where track STRe+2 is not superimposed. However, the radial width d1 of the area within track STRe where track STRe+1 is not superimposed is different from the radial width d1 of the area within track STRe+1 where track STRe+2 is not superimposed.

[0054] In Figure 4, for the sake of explanation, each track STR is shown as a rectangle, but in reality, each track STR is curved along the circumference. Furthermore, each track STR may be wavy, extending circumferentially while fluctuating radially d1. Note that in Figure 4, three track STRs are superimposed, but two track STRs may be superimposed, or more than three track STRs may be superimposed.

[0055] The write processing unit 62 can select a tile recording format in which data is written to multiple tracks STR in the overlay direction d5 and cause the write head WHD to write data to each band BA. In the example shown in Figure 4, the write processing unit 62 sequentially records data to tracks STRe to STRe+2 in the band BAe with a pitch STP toward the inward direction (overlay direction d5). Since the user data area U is an area where data is written in the tile recording format, the recording density of the user data area U can be improved.

[0056] The light processing unit 62 lights track STre+1 inward of track STre with pitch STP, overwriting track STre+1 onto a portion of the inner circumference of track STre. The light processing unit 62 lights track STre+2 inward of track STre+1 with pitch STP, overwriting track STre+2 onto a portion of the inner circumference of track STre+1.

[0057] Figure 5 is a schematic diagram showing the three tracks CTR and the write head WHD of the media cache M where the normal recording process of disk DK shown in Figure 3 takes place. The media cache M and the system area S shown in Figure 3 are normal recording areas. Random data writing is permitted in the media cache M and system area S; in other words, normal recording is permitted.

[0058] As shown in Figure 5, the media cache M has multiple tracks CTR, including tracks CTRe, CTRe+1, and CTRe+2. Each of the multiple tracks CTR is a data track. For example, the radial width d1 (track width) of tracks CTRe, CTRe+1, and CTRe+2 is the same. However, the track widths of tracks CTRe to CTRe+2 may be different from each other.

[0059] Track CTRe has a track center CTCe at the center of radial d1, track CTRe+1 has a track center CTCe+1 at the center of radial d1, and track CTRe+2 has a track center CTCe+2 at the center of radial d1. In the example shown in Figure 5, tracks CTRe, CTRe+1, and CTRe+2 are written at pitch (normal recording track pitch) CTP. The track center CTCe of track CTRe and the track center CTCe+1 of track CTRe+1 are separated by pitch CTP. The track center CTCe+1 of track CTRe+1 and the track center CTCe+2 of track CTRe+2 are separated by pitch CTP.

[0060] Tracks CTRe and CTRe+1 are separated by a gap GP. Tracks CTRe+1 and CTRe+2 are separated by a gap GP. Tracks CTRe to CTRe+2 may be lit at different pitches. In Figure 5, for the sake of explanation, each track CTR is shown as a rectangle, but in reality, each track CTR is curved along the circumference. Furthermore, each track CTR may be wavy, extending circumferentially while fluctuating in the radial direction d1.

[0061] The write processing unit 62 can select a normal recording format in which data is written to multiple tracks CTR at intervals in the radial direction d1 of the disk DK and perform the write process. In the example shown in Figure 5, the write processing unit 62 positions the write head WHD on the track center CTCe in a predetermined area of ​​the disk DK and performs normal recording on track CTRe or a predetermined sector of track CTRe.

[0062] The write processing unit 62 positions the write head WHD at track center CTCe+1, which is located inward from track center CTCe of track CTRe by a pitch CTP, and normally records track CTRe+1 or a predetermined sector of track CTRe+1. The write processing unit 62 positions the write head WHD at track center CTCe+2, which is located inward from track center CTCe+1 of track CTRe+1 by a pitch CTP, and normally records track CTRe+2 or a predetermined sector of track CTRe+2.

[0063] The write processing unit 62 may sequentially record tracks CTRe, CTRe+1, and CTRe+2 in a predetermined area of ​​disk DK, or it may randomly record them in predetermined sectors of track CTRe, track CTRe+1, and track CTRe+2.

[0064] Figure 6 is a schematic diagram illustrating an example of data writing in disk DK. Tracks STR and CTR are data tracks, respectively. As shown in Figure 6, the user data area U has bands BAa, BAb, and BAc. Bands BAa, BAb, and BAc belong to the same zone Ze. In zone Ze, bands BAa, BAb, and BAc are arranged intermittently in the overlay direction in the order they are described.

[0065] Bands BAa and BAb are adjacent in the radial direction d1, and bands BAb and BAc are adjacent in the radial direction d1. Band BAa contains x tracks: STRa0, STRa1, STRa2, ..., STRa(x-3), STRa(x-2), and STRa(x-1). Tracks STRa0 through STRa(x-1) are recorded in the order listed above in the overwriting direction d5. In band BAa, track STRa0 corresponds to the first track on which data is written, and track STRa(x-1) corresponds to the last track on which data is written.

[0066] Band BAb contains x tracks: STRb0, STRb1, STRb2, ..., STRb(x-3), STRb(x-2), and STRb(x-1). Tracks STRb0 through STRb(x-1) are recorded in the order listed above in the overlay direction d5. In band BAb, track STRb0 corresponds to the first track on which data is written, and track STRb(x-1) corresponds to the last track on which data is written.

[0067] Band BAc contains x tracks: STRc0, STRc1, STRc2, ..., STRc(x-3), STRc(x-2), and STRc(x-1). Tracks STRc0 through STRc(x-1) are recorded in the order listed above in the overlay direction d5. In band BAc, track STRc0 corresponds to the first track on which data is written, and track STRc(x-1) corresponds to the last track on which data is written.

[0068] Each band BA belonging to the same zone Z has the same number of track STRs. For example, each band BA belonging to zone Ze has the same number of track STRs. In other words, the number of track STRs that each band BA has is fixed for each zone Z. In this example, each band BA belonging to zone Ze has x track STRs.

[0069] Figure 6 shows tracks CTR(x-2) and CTR(x-1). In Figure 6, tracks CTR(x-2) and CTR(x-1) are normally recorded in the media cache M or system area S. Tracks CTR(x-2) and CTR(x-1) are adjacent in the radial direction d1.

[0070] Figure 7 is a schematic diagram showing two bands BAa and BAb and one guard band GB within the user data area U shown in Figure 6. As shown in Figure 7, unlike the normal recording method, the tile recording method has the characteristic of overwriting a portion of track STR, so the MPU60 manages the track groups of the user data area U in units called bands.

[0071] Generally, a guard band GB is provided between adjacent bands BA in the radial direction d1. The guard band GB includes a guard track GTR. Unlike this embodiment, the guard band GB may include multiple guard tracks GTR. The guard band GB plays a role in suppressing interference between adjacent bands BA. The guard band GB makes it possible to perform sequential recording in units of one band BA. In addition, the guard band GB makes it possible to separate the range (band BA) to be written sequentially.

[0072] For example, the track centers STCa(x-3) of track STRa(x-3), STCa(x-2) of track STRa(x-2), STCa(x-1) of track STRa(x-1), GTC of guard track GTR, STCb0 of track STRb0, STCb1 of track STRb1, and STCb2 of track STRb2 are all positioned at equal pitches in the overlapping direction d5.

[0073] With the exception of the guard band GB, the recording capacity of each band BA in the user data area U is usually predetermined based on the user's requirements. The MPU60 can record the same amount of data in each band BA. Generally, the recording capacity of each band BA is 128 MiB or 256 MiB.

[0074] Figure 8 is a schematic diagram showing three sectors SCe, SC(e+1), and SC(e+2) of track STRa0 in band BAa shown in Figure 6. As shown in Figure 8, each track STR has multiple sectors SC. Track STRa1 has multiple sectors SC, including sectors SCe, SC(e+1), and SC(e+2).

[0075] If we consider sector SC(e+1) as the nth sector among the multiple sectors SC of track STRa0, then sector SC(e+2) is the (n+1)th sector following sector SC(e+1) in the direction of travel d2, and sector SCe is the (n-1)th sector located before sector SC(e+1) in the direction of travel d2. Each track STR belonging to the same zone Z has the same number of sectors SC. In this embodiment, each track STR belonging to zone Ze has y sectors SC.

[0076] Each sector SC has a length Ls in the circumferential direction of disk DK. Each sector SC may also be a split sector, divided by a servo sector SV. In this case, the length of sector SC does not have to be Ls. The light head (WHD) is a magnetic head for energy-assisted magnetic recording (EAMR). In this embodiment, the light head (WHD) is configured to utilize energy other than magnetic energy, but it is not limited to this configuration; the light head (WHD) may be a magnetic head that is not configured to perform energy-assisted recording.

[0077] Figure 9 is a schematic diagram showing the two bands BAa and BAb shown in Figure 7, and one guard band GB, and is a diagram for explaining multiple target sectors RSC and multiple unused sectors VSC. In Figure 9, for illustrative purposes, each track STR is shown as a rectangle; however, in reality, each track STR is curved along the circumference. Also, while multiple track STRs are shown aligned in the overlapping direction d5 without overlapping, in reality, multiple track STRs overlap while aligned in the overlapping direction d5. Furthermore, in the figure, the target sector RSC is marked with a dot pattern. Unused sector VSC is represented as blank.

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

[0079] In this embodiment, band BAa is a band adjacent to band BAb and is positioned above band BAb in the overlay direction d5. Each track STR in band BAa contains G target sector RSCs (one or more target sector RSCs) on which valid data has been written. For example, track STRa0 has y target sector RSCs (G=y). All sector SCs in track STRa0 are target sector RSCs. Track STRa(x-1) has 5 target sector RSCs (G=5). The remaining sector SCs in track STRa(x-1) are unused sector VSCs on which no valid data has been written. From the above, the number of target sector RSCs in track STRa0 is different from the number of target sector RSCs in track STRa(x-1).

[0080] In each band BA of Zone Ze, all sector SCs of the x-1 tracks STR from 0 to x-2 are target sector RSCs and recording sector USCs with valid data written to them. In the x-1 track STR of each band BA in Zone Ze, the five sector SCs from 0 to 4 are target sector RSCs and recording sector USCs. On the other hand, in the x-1 track STR, the remaining sector SCs from 5 to y-1 are unused sector VSCs with no valid data written to them.

[0081] Figure 10 is a schematic diagram showing an example of a first track STR0 and a second track STR1, assuming that the magnetic disk drive 1 does not have a function to perform error correction on the data of track TR. It is a diagram for explaining the write process to the first track STR0 and the second track STR1. It is a diagram for explaining the state in which the write process to the second track STR1 is continued until the sector-by-sector error correction for the first track STR0 reaches its limit. It is a diagram that shows the change in the bit error rate (BER) for the first track STR0 and the change in BER with respect to the position error (PE) as graphs. In the explanation using Figure 10, the magnetic disk drive 1 is described as not having the error correction unit 64 of Figure 1. Also, in Figure 10, for the sake of explanation, the first track STR0, etc. are drawn as if the circumferential direction is a straight line.

[0082] As shown in Figure 10, in the recording layer L, multiple tracks STR are adjacent in the radial direction d1. The first track STR0 and the second track STR1 are data tracks, adjacent to each other, and all sectors SC of the first track STR0 and all sectors (data sectors) SC of the second track STR1 are target sectors RSC, respectively. The write operation to the first track STR0 is performed ideally without positioning error PE (PE ≈ 0, or PE = 0).

[0083] If the magnetic disk drive 1 is affected by external vibrations during the write process, a positioning error PE occurs when positioning the write head WHD. The positioning error PE is the amount of deviation of the write head WHD from the target position in the radial direction d1. By setting the track margin TM, it is possible to determine the acceptable range within which it is guaranteed that data on adjacent tracks can be read.

[0084] For example, if a write operation is performed on the second track STR1, and the target sectors RSCe, RSC(e+1), and RSC(e+2) of the first track STR0 are adjacent to the light head WHD in the radial direction d1 during the period when the positioning error PE exceeds the track margin TM, then the data in target sectors RSCe, RSC(e+1), and RSC(e+2) of the first track STR0 is judged (expected) to be corrupted. A lower BER for the data is desirable, but the BER of the data in target sectors RSCe, RSC(e+1), and RSC(e+2) of the first track STR0 exceeds the threshold BERTH. As can be seen from the graph on the right side of Figure 10, the larger the positioning error PE, the greater the adverse effect of ATI (Adjacent Track Interference), and the BER of the data in the first track STR0, which is excessively affected by the adverse effect of ATI, becomes excessively high.

[0085] Therefore, among the multiple target sector RSCs of the first track STR0, target sector RSCe, target sector RSC(e+1), and target sector RSC(e+2) are determined to be corrupted sector CSC1, target sector CSC2, and target sector CSC3. This can lead to a deterioration in the quality of the signal obtained by reading the data from corrupted sectors CSC1 to CSC3, or the erasure of the data from corrupted sectors CSC1 to CSC3.

[0086] In the example explained using Figure 10, the magnetic disk drive 1 does not have the function to perform track-level error correction on the data of track TR. Here, track-level error correction is also called track ECC (Error Checking and Correcting). Therefore, target sectors RSCe, RSC(e+1), and RSC(e+2) remain as corrupted sectors CSC1, CSC2, and CSC3.

[0087] Here, in Figure 10, it is assumed that all target sector RSCs of track TR have a common track margin TM. In the explanations of Figures 11 and 12 described later, it is also assumed that all target sector RSCs of track TR have a common track margin TM. However, the above setting of track margin TM is just an example, and the track margin TM may be different for each target sector RSC.

[0088] Figure 11 is a schematic diagram showing an example of a first track STR0 and a second track STR1, assuming that the magnetic disk drive 1 does not have a function to perform track-level error correction on the data of track TR. It is a diagram for explaining the write process for the first track STR0 and the second track STR1. It is a diagram for explaining the state in which the write process for the second track STR1 is terminated when the judgment value is set to a write-off track slice WOS that is smaller (stricter) than the track margin TM and the positioning error PE is detected to have exceeded the reference radius position PO. It is a diagram that shows the change in BER for the first track STR0 and the change in BER for the positioning error PE, respectively, as graphs. In Figure 11, for the sake of explanation, the first track STR0, etc., are drawn as if the circumferential direction is a straight line. In the explanation using Figure 11, the magnetic disk drive 1 is described as not having the error correction unit 64 of Figure 1.

[0089] As shown in Figure 11, the first track STR0 and the second track STR1 are data tracks, and all sectors SC of the first track STR0 and all sectors (data sectors) SC of the second track STR1 are target sectors RSC, respectively. The write operation to the first track STR0 is performed ideally without positioning error PE (PE ≈ 0, or PE = 0). The first track STR0 is located in a first direction Da parallel to the radial direction d1 when viewed from the second track STR1. The write processing unit 62 can select a recording format in which the data of the second track STR1 is written over the data of the first track STR0 in the overwriting direction d5, which is opposite to the first direction Da.

[0090] To prevent or suppress the write process in a state where the positioning error PE exceeds the track margin TM, the magnetic disk drive 1 has a write-off track slice WOS. The reference radius position PO is a position offset by the write-off track slice WOS in the first direction Da from the track center STC1 of the second track STR1. During the period of writing data to the second track STR1, when it is determined that the positioning error PE has exceeded the reference radius position PO, the writing of data to the second track STR1 can be paused. Among the plurality of target sectors RSC of the second track STR1, the remaining target sectors RSC for which the writing of data has been postponed become empty sectors ESC where no data has been written. By avoiding a situation where the positioning error PE exceeds the track margin TM, the occurrence of damaged target sectors CSC in the first track STR0 can be prevented.

[0091] Note that the track STR has servo sectors in addition to the sector SC which is a data sector. In the track STR, generally, the data sectors and the servo sectors are arranged alternately. The head HD (read head RHD) can derive the positioning error PE together with the servo sectors. Therefore, generally, the positioning error PE is information obtained intermittently.

[0092] In order not to have PE > TM, it is necessary to set the write-off track slice WOS so that WOS ≤ TM. To avoid a situation where PE > TM, it is desirable to set the write-off track slice WOS so that WOS < TM. Thereby, before the positioning error PE exceeds the track margin TM, the write process for the second track STR1 can be paused, and a situation where the quality of the data in the first track STR0 deteriorates can be avoided.

[0093] However, it should be noted that setting the write-off track slice WOS to a small value makes write operations more likely to be interrupted, leading to a decrease in the write performance of the magnetic disk drive 1. In the case of the magnetic disk drive 1, which does not have a function to perform track-level error correction, if write operations to the second track STR1 are interrupted, a write retry process is executed, which waits for the disk DK to rotate until PE ≤ WOS before resuming write operations to the second track STR1. The write retry process allows the free sector ESC of the second track STR1 to be changed to the recording sector USC, thus avoiding a situation where the utilization efficiency of the second track STR1 remains low.

[0094] Here, in Figure 11, it is assumed that all target sector RSCs of track TR have a common write-off track slice WOS. In the explanation of Figure 12, which will be described later, it is also assumed that all target sector RSCs of track TR have a common write-off track slice WOS. However, the above setting of the write-off track slice WOS is just an example, and the write-off track slice WOS may be different for each target sector RSC.

[0095] Figure 12 is a schematic diagram showing an example of a first track STR0 and second track STR1 of a magnetic disk drive 1 that has a function to perform track-level error correction on the data of track TR. It is a diagram to explain the write process for the first track STR0 and second track STR1. It is a diagram to explain a state in which the write-off track slice WOS is set to a value greater than (looser than) the track margin TM, and the write process for the second track STR1 is continued until the track-level error correction for the first track STR0 reaches its limit. The diagram shows the change in BER for the first track STR0 and the change in BER for the positioning error PE, respectively, as graphs. In Figure 12, for the sake of explanation, the first track STR0, etc., are drawn as if the circumferential direction is a straight line.

[0096] As shown in Figure 12, the light operation on the first track STR0 is performed ideally without positioning error PE (PE ≈ 0, or PE = 0). The magnetic disk device 1 is equipped with an error correction unit 64. When a corrupted sector CSC occurs on track ST, the read processing unit 63, together with the head amplifier IC 130, can detect that a corrupted sector CSC has occurred on track ST, and the error correction unit 64 can perform error correction processing to recover the data of the corrupted sector CSC. For example, if a corrupted sector CSC occurs on the first track STR0, the error correction unit 64 can recover the data of the corrupted sector CSC based on the data of multiple target sector RSCs and parity sector data on the first track STR0.

[0097] The above parity sector is generated based on the data of multiple target sector RSCs of the first track STR0 and can be provided in a portion of the multiple target sector RSCs of the first track STR0. For example, one or two target sector RSCs of the first track STR0 can be used as the parity sector. However, the above parity sector may be provided in a track TR other than the first track STR0. Alternatively, the above parity sector may be provided in memory other than disk (for example, non-volatile memory 90).

[0098] As described above, even if a corrupted sector CSC occurs on the first track STR0, the error correction unit 64 can perform error correction processing to recover the data of the corrupted sector CSC, thus allowing the occurrence of a corrupted sector CSC on the first track STR0 to be tolerated. In a magnetic disk device 1 equipped with an error correction unit 64, the write-off track slice WOS can be set such that WOS ≥ TM, making it difficult for the write process to terminate and suppressing a decrease in the write performance of the magnetic disk device 1.

[0099] It should be noted that there is an upper limit on the number of corrupted sectors that the error correction unit 64 can perform error correction on a track-by-track basis. For example, if the number of corrupted sectors CSC on the first track STR0 exceeds the upper limit (e.g., 12), it will be difficult for the error correction unit 64 to recover the data from all of the corrupted sectors CSC.

[0100] Figure 13 is a table showing the presence or absence of track ECC, the function name for controlling DOL, the processing when the positioning error PE exceeds the reference radius position PO, the setting of the predicted upper threshold, and the setting of the predicted excess amount for the first to third methods of the first and second write operations. As shown in Figures 13, 11, and 1, assuming that the magnetic disk drive 1 does not have the track ECC function, the magnetic disk drive 1 can adopt the first write operation. The function name for controlling DOL (Drift-Off Level) is DDOL (Dynamic Drift-Off Level). The first write operation corresponds to the write operation shown using Figure 11.

[0101] If, during the first write period while performing write operations on the second track STR1, the positioning error PE exceeds the reference radius position PO, the write operation on the second track STR1 is paused before the positioning error PE exceeds the track margin TM. Subsequently, a write retry process is executed, which waits for disk DK to rotate until PE ≤ WOS, and then resumes the write operation on the second track STR1.

[0102] However, if the magnetic disk drive 1 employs the first write operation, write retry processes such as waiting for disk DK to rotate may occur frequently, making it difficult to improve the write performance of the magnetic disk drive 1. Therefore, in order to improve the write performance of the magnetic disk drive 1, the magnetic disk drive 1 employing the second write operation has a track ECC function. In the magnetic disk drive 1 employing the second write operation, the function name for controlling DOL is iDDOL (intelligence Dynamic Drift-Off Level). This allows for a certain number of corrupted sectors (CSCs) to occur in the track STR, improving TPI (Tracks Per Inch).

[0103] (Second method of second light operation) (Predicted upper threshold: constant) Next, we will explain the second method of the second write operation. Here, the prediction upper threshold is treated as a constant. As shown in Figures 13, 1, and 12, the error correction unit 64 can perform error correction on the data of one or more corrupted target sectors CSC among the multiple target sectors RSC of the first track STR0 that are determined to have corrupted data.

[0104] Here, we focus on the first write period, which is the period after the write processing unit 62 has performed write operations on multiple target sector RSCs of the first track STR0, and the period during which it performs write operations on multiple target sector RSCs of the second track STR1.

[0105] During the first write period, the read processing unit 63 performs a first seek operation to seek the read head RHD, moving the read head RHD by a first distance and positioning the write head WHD opposite the second track STR1. For example, when performing a write operation to the second track STR1 immediately following a write operation to the first track STR0, the first distance corresponds to the distance by which the read head RHD is moved by one track.

[0106] The adjustment unit 65 derives a first predicted excess amount, which is the expected amount by which the position of the light head WHD will extend beyond the reference radius position PO in the first direction Da during the first light period. The first predicted excess amount is an amount that varies depending on the distance the read head RHD is sought (seek distance). The adjustment unit 65 can adjust the first predicted excess amount and other predicted excess amounts according to the seek distance. For example, if the first distance corresponds to the distance required to move the read head RHD by one track, the adjustment unit 65 adjusts the predicted excess amount to the minimum predicted excess amount that minimizes the predicted excess amount. Furthermore, the adjustment unit 65 derives a predicted upper threshold value that indicates the limit of the range in which error correction is possible for the first track STR0. The predicted upper threshold value is a constant.

[0107] Each time data is written to each target sector RSC of the second track STR1, the correction limit prediction unit 66 measures the actual excess amount by which the position of the light head WHD extends beyond the reference radius position PO in the first direction Da, updates the cumulative actual excess amount which is the sum of the actual excess amounts, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount. Here, the cumulative measured excess represents the estimated amount of data corruption in the first track STR0 at the point when the write operation has been performed up to the target sector RSC, which is opposite the write head WHD, in the second track STR1. The first cumulative predicted excess represents the expected amount of data corruption in the first track STR0, assuming that the write head WHD is positioned opposite the next target sector RSC following the direction of travel d2 and a write operation is performed on that target sector RSC.

[0108] If the determination unit 67 determines that the first cumulative predicted excess amount is below the prediction upper threshold, it can instruct the write processing unit 62 to continue writing to the second track STR1. Furthermore, if the determination unit 67 determines that the first cumulative predicted excess amount has exceeded the prediction upper threshold, it can cause the write processing unit 62 to pause (or terminate) the write processing for the second track STR1.

[0109] As described above, in the second method of the second write operation, the predicted excess amount can be adjusted according to the seek distance. For example, consider the case where the first distance corresponds to the distance the read head RHD moves by one track. When the second method of the second write operation is adopted, the adjustment unit 65 adjusts the predicted excess amount to the minimum predicted excess amount. On the other hand, when the first method of the second write operation is adopted, the adjustment unit 65 adjusts the predicted excess amount to the maximum predicted excess amount. This is because, in the first method of the second write operation, the predicted excess amount is always fixed at the maximum predicted excess amount.

[0110] Compared to the first method of second write operation, the second method of second write operation does not cause the cumulative predicted excess amount to become excessively large, thus reducing the frequency of pausing (or terminating) the write operation to the second track STR1. Furthermore, when the write operation is terminated, the frequency of activating PTS (Partial Track Slip), which saves the remaining data that could not be written to the second track STR1, can be reduced. The second method of second write operation can contribute to improving the write performance of the magnetic disk device 1.

[0111] Now, let's focus on the target sector RSCn of the second track, STR1n. Multiple target sector RSCs on the second track STR1 include the nth target sector RSCn and the (n+1)th target sector RSC(n+1) that follows the nth target sector RSCn in the direction of travel d2.

[0112] During the first write period described above, the write processing unit 62 performs write processing up to the nth target sector RSCn of the second track STR1. The correction limit prediction unit 66 measures the actual excess amount, updates the cumulative actual excess amount, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount. The first predicted excess amount is the amount by which the position of the write head WHD is expected to extend beyond the reference radius position PO in the first direction Da, assuming that data is written to the (n+1)th target sector RSC(n+1) during the first write period.

[0113] If the determination unit 67 determines that the first cumulative predicted excess amount is less than or equal to the prediction upper limit threshold, it can cause the write processing unit 62 to continue writing to the (n+1)th target sector RSC(n+1) of the second track STR1. Furthermore, if the determination unit 67 determines that the first cumulative predicted excess amount has exceeded the prediction upper limit threshold, it can cause the write processing unit 62 to pause (or terminate) the write operation for the (n+1)th target sector RSC(n+1) of the second track STR1.

[0114] Next, we will focus on predicted excess amounts, such as the first predicted excess amount. If the above-mentioned first distance is less than or equal to the distance required to move the read head RHD by one track in the radial direction d1, the adjustment unit 65 can adjust the first predicted excess amount (predicted excess amount) to the minimum predicted excess amount. On the other hand, if the first distance is greater than or equal to the distance required to move the read head RHD by two tracks in the radial direction d1, the adjustment unit 65 can adjust the first predicted excess amount (predicted excess amount) to an amount greater than the minimum predicted excess amount. Furthermore, because the seek operation employs technology to reduce head sway, the above predicted excess amount is not proportional to the seek distance. However, it is expected that head HD sway will be greater when the seek distance is two tracks or more than when it is one track or less. Therefore, when the seek distance is two tracks or more, the predicted excess amount is adjusted to be greater than the minimum predicted excess amount (Figure 14). Note that the values ​​on the vertical axis in Figure 14 are examples and can be varied in various ways.

[0115] Here, we will explain the seek action, which can reduce head wobble. The period during which the read processing unit 63 performs the seek process includes an acceleration period, which is the first period, and a deceleration period, which is the last period. During the acceleration period, the read processing unit 63 seeks the read head RHD while gradually increasing the speed in the first seek direction. During the deceleration period, the read processing unit 63 seeks the read head RHD while gradually decreasing the speed in the first seek direction. When the read head RHD seeks onto the second track STR1 from the outer circumference, the first seek direction is inward, and when the read head RHD seeks onto the second track STR1 from the inner circumference, the first seek direction is outward.

[0116] Instead of seeking the read head RHD at a constant speed, the read head RHD is sought using ease-in and ease-out. This suppresses abrupt changes in the speed of the read head RHD during seeking, thereby reducing the risk of exciting the resonant frequency of the mechanical system. By adopting this type of seek operation together with the second method of the second write operation, it is possible to improve the write performance of the magnetic disk drive 1.

[0117] Next, we will explain the case where a seek operation is inserted in the middle of the write operation to the second track STR1. Here, we focus on the nth target sector RSCn. If, during the first write period, write processing is performed up to the nth target sector RSCn of the second track STR1, and after the first write period the read head RHD is made to seek, and then during the second write period write processing is resumed from the (n+1)th target sector RSC(n+1) of the second track STR1, then during the first write period, the write processing unit 62 and the correction limit prediction unit 66 perform the following processing.

[0118] The write processing unit 62 performs write operations up to the nth target sector RSCn of the second track STR1. The correction limit prediction unit 66 measures the actual excess amount, updates the cumulative actual excess amount, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount. The first predicted excess amount is the amount by which the position of the light head WHD is expected to extend beyond the reference radius position PO in the first direction Da, assuming that data is written to the (n+1)th target sector RSC(n+1) during the first write period.

[0119] During the second write period, the read processing unit 63, adjustment unit 65, correction limit prediction unit 66, and determination unit 67 perform the following processes. The read processing unit 63 performs a second seek operation to seek the read head RHD, moves the read head RHD by a second distance, and positions the write head WHD facing the second track STR1 again. The adjustment unit 65 re-derives a second predicted excess amount, which is the amount by which the position of the light head WHD is expected to extend beyond the reference radius position PO in the first direction Da during the second light period. The second predicted excess amount is the amount corresponding to the second distance.

[0120] The correction limit prediction unit 66 recalculates the second cumulative predicted excess amount by adding the second predicted excess amount to the cumulative measured excess amount. The second predicted excess amount is the amount by which the position of the light head WHD is expected to extend beyond the reference radius position PO in the first direction Da, assuming that data is written to the (n+1)th target sector RSC(n+1) during the second write period. If the determination unit 67 determines that the second cumulative predicted excess amount is less than or equal to the prediction upper limit threshold, it can cause the write processing unit 62 to resume the write operation for the (n+1)th target sector RSC(n+1) of the second track STR1. Furthermore, if the determination unit 67 determines that the second cumulative predicted excess amount has exceeded the prediction upper limit threshold, it can cause the write processing unit 62 to pause (or terminate) the write operation for the (n+1)th target sector RSC(n+1) of the second track STR1. As described above, if the magnetic disk drive 1 adopts the second method of the second write operation, the predicted excess amount can be adjusted, thereby improving the write performance of the magnetic disk drive 1.

[0121] By the way, if the seek distance is 2 tracks or more, the predicted excess is adjusted to be greater than the minimum predicted excess. Therefore, compared to the case where the seek distance is 1 track or less, There is a risk that the frequency of pausing (or terminating) write operations to the second track STR1 may increase. Furthermore, if write operations are terminated, there is a risk that the frequency of PTS activation, which backs up any remaining data that could not be written to the second track STR1, may increase. Therefore, the magnetic disk device 1, which employs the third method of second write operation, can adjust the predicted excess amount to a smaller amount by performing a disk DK rotation waiting operation when the write operation to the second track STR1 is paused.

[0122] (Third method of second light operation) (Predicted upper threshold: constant) Next, we will explain the third method of the second write operation. Here, the prediction upper threshold will be treated as a constant. If, during the first write period, the first distance the read processing unit 63 moves the read head RHD is greater than or equal to the distance of two data tracks, and the first predicted excess amount adjusted by the adjustment unit 65 is greater than the minimum amount, and the determination unit 67 determines that the first cumulative predicted excess amount exceeds the prediction upper limit threshold, then the correction limit prediction unit 66 and the determination unit 67 execute the following processes.

[0123] The correction limit prediction unit 66 further calculates the minimum cumulative predicted excess amount by adding the above minimum predicted excess amount to the cumulative measured excess amount. If the determination unit 67 determines that the minimum cumulative predicted excess amount is below the predicted upper threshold, it controls the drive of the write processing unit 62, pauses the write operation for the second track STR1, maintains the position of the write head WHD in the radial direction d1, waits for the disk DK to rotate, and then transitions to a write retry operation to resume the write operation. As a result, compared to the second method of the second write operation, the frequency of PTS activation can be reduced, and the utilization efficiency of track STR can be improved. Furthermore, since activating PTS results in a longer delay in command processing than a write retry operation, having the option to switch to a write retry operation is effective in improving write performance.

[0124] Furthermore, if the determination unit 67 determines that the minimum cumulative predicted excess amount exceeds the predicted upper threshold, it can instruct the write processing unit 62 to terminate the write operation for the second track STR1 and save the remaining data that could not be written to the second track STR1 to a recording area other than the first track STR0 and the second track STR1. Examples of recording areas other than the first track STR0 and the second track STR1 include tracks on the disk DK, such as the third track STR, which is located in the overwriting direction d5 from the perspective of the second track STR1 and is adjacent to the second track STR1. The recording areas other than the first track STR0 and the second track STR1 may also be storage media outside the disk DK.

[0125] (Second method of second light operation) (Predicted upper threshold: variable) Next, we will describe another example of the second method of the second Wright operation. Here, we will treat the prediction upper threshold as a variable. Furthermore, the second method of the second Wright operation that treats the prediction upper threshold as a variable is the same as the second method of the second Wright operation that treats the prediction upper threshold as a constant, except for what is described here. As shown in Figures 13, 1, and 12, we focus on the first write period, which is the period after the write processing unit 62 has performed write processing on multiple target sector RSCs of the first track STR0, and the period during which it performs write processing on multiple target sector RSCs of the second track STR1.

[0126] During the first write period, the read processing unit 63 executes the first seek process described above, and positions the write head WHD opposite the second track STR1. The adjustment unit 65 derives the first predicted excess amount. Furthermore, the adjustment unit 65 derives a prediction upper threshold that indicates the limit of the range in which error correction is possible for the first track STR0. The prediction upper threshold is a variable. The prediction upper threshold has a smaller value as each prediction excess, including the first prediction excess, increases. The correction limit prediction unit 66 calculates the first cumulative predicted excess amount each time data is written to each target sector RSC of the second track STR1. If the determination unit 67 determines that the first cumulative predicted excess amount is below the prediction upper threshold, it can instruct the write processing unit 62 to continue writing to the second track STR1. Furthermore, if the determination unit 67 determines that the first cumulative predicted excess amount has exceeded the prediction upper threshold, it can cause the write processing unit 62 to pause (or terminate) the write processing for the second track STR1.

[0127] As described above, in the second method of the second write operation, which treats the prediction upper threshold as a variable, the prediction excess amount can be adjusted according to the seek distance. Also, in the second method of the second write operation, which treats the prediction upper threshold as a variable, the prediction upper threshold is a variable. For example, if the first distance corresponds to the distance that moves the read head RHD by one track, the adjustment unit 65 can adjust the first prediction excess amount to the minimum prediction excess amount, adjust the first cumulative prediction excess amount to the minimum, and adjust the prediction upper threshold to the maximum prediction upper threshold amount. Since the first cumulative prediction excess amount is set to be less likely to exceed the prediction upper threshold, it is possible to make it easier to continue the write operation to the second track STR1.

[0128] On the other hand, if the first distance corresponds to the distance by which the read head RHD moves by two tracks or more, and the adjustment unit 65 adjusts the first predicted excess amount to the maximum predicted excess amount, and also adjusts the first cumulative predicted excess amount to the maximum, the adjustment unit 65 can adjust the predicted upper limit threshold to the minimum predicted upper limit threshold. Since the first cumulative predicted excess amount is set to easily exceed the predicted upper limit threshold, it is possible to pause (or terminate) the write operation for the second track STR1. A second method of the second write operation, which treats the predicted upper threshold as a variable, can also contribute to improving the write performance of the magnetic disk device 1.

[0129] Next, we will focus on the predicted excess amounts, such as the first predicted excess amount, and the predicted upper threshold. If the above-mentioned first distance is less than or equal to the distance required to move the read head RHD by one track in the radial direction d1, the adjustment unit 65 can adjust the first predicted excess amount (predicted excess amount) to the minimum predicted excess amount and adjust the predicted upper limit threshold to the maximum predicted upper limit threshold. On the other hand, if the first distance is greater than or equal to the distance required to move the read head RHD by two tracks in the radial direction d1, the adjustment unit 65 can adjust the first predicted excess amount (predicted excess amount) to an amount greater than the minimum predicted excess amount, and adjust the predicted upper limit threshold to a value smaller than the maximum predicted upper limit threshold.

[0130] Next, we will explain the case where a seek operation is inserted in the middle of the write operation to the second track STR1. Here, we focus on the nth target sector RSCn. If, during the first write period, write processing is performed up to the nth target sector RSCn of the second track STR1, and after the first write period the read head RHD is made to seek, and then during the second write period write processing is resumed from the (n+1)th target sector RSC(n+1) of the second track STR1, then during the first write period, the write processing unit 62 and the correction limit prediction unit 66 perform the following processing.

[0131] The write processing unit 62 performs write operations up to the nth target sector RSCn of the second track STR1. The correction limit prediction unit 66 measures the actual excess amount, updates the cumulative actual excess amount, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount.

[0132] During the second write period, the read processing unit 63, adjustment unit 65, correction limit prediction unit 66, and determination unit 67 perform the following processes. The read processing unit 63 executes the second seek process described above and positions the write head WHD opposite the second track STR1 again. The adjustment unit 65 re-derives the second predicted excess amount. Furthermore, the adjustment unit 65 adjusts the prediction upper threshold to a value corresponding to the second predicted excess amount. The correction limit prediction unit 66 adds the second predicted excess amount to the cumulative actual excess amount and recalculates the second cumulative predicted excess amount.

[0133] If the determination unit 67 determines that the second cumulative predicted excess amount is less than or equal to the prediction upper limit threshold, it can cause the write processing unit 62 to resume the write operation for the (n+1)th target sector RSC(n+1) of the second track STR1. Furthermore, if the determination unit 67 determines that the second cumulative predicted excess amount has exceeded the prediction upper limit threshold, it can cause the write processing unit 62 to pause (or terminate) the write operation for the (n+1)th target sector RSC(n+1) of the second track STR1.

[0134] Furthermore, the second method of the second write operation, which treats the predicted upper threshold as a variable, can also adjust the predicted excess amount to a smaller amount by performing a disk DK rotation waiting operation when the write operation to the second track STR1 is paused.

[0135] (Third method of second light operation) (Predicted upper threshold: variable) Next, we will describe another example of the third method of the second Wright operation. Here, we will treat the upper limit of the prediction threshold as a variable. Furthermore, the third method of the second Wright operation that treats the upper limit of the prediction threshold as a variable is the same as the third method of the second Wright operation that treats the upper limit of the prediction threshold as a constant, except for what is described here.

[0136] If, during the first write period, the first distance the read processing unit 63 moves the read head RHD is greater than or equal to the distance of two data tracks, the first predicted excess amount adjusted by the adjustment unit 65 is greater than the minimum amount, the predicted upper limit threshold adjusted by the adjustment unit 65 is less than the maximum predicted upper limit threshold, and the determination unit 67 determines that the first cumulative predicted excess amount exceeds the predicted upper limit threshold, then the correction limit prediction unit 66 and the determination unit 67 execute the following processes.

[0137] The correction limit prediction unit 66 further calculates the minimum cumulative predicted excess amount by adding the above minimum predicted excess amount to the cumulative measured excess amount. If the determination unit 67 determines that the minimum cumulative predicted excess amount is below the predicted upper threshold, it controls the drive of the write processing unit 62, pauses the write operation for the second track STR1, maintains the position of the write head WHD in the radial direction d1, waits for the disk DK to rotate, and then transitions to a write retry operation to resume the write operation. This reduces the frequency of PTS activation and improves the utilization efficiency of track STR.

[0138] Furthermore, if the determination unit 67 determines that the minimum cumulative predicted excess amount exceeds the prediction upper threshold, it can instruct the write processing unit 62 to terminate the write process for the second track STR1 and save the remaining data that could not be written to the second track STR1 to a recording area other than the first track STR0 and the second track STR1.

[0139] (Examples of the second and third methods of the second light operation) (Predicted upper threshold: constant) Next, the second and third methods of the second write operation will be explained exemplified. Here, the predicted upper threshold will be treated as a constant. Figure 15 shows the change in positioning error PE, the change in cumulative excess amount, and the change in cumulative predicted excess amount when a write operation is performed on the second track STR1 using the second and third methods of the second write operation, and is a figure that shows the case when the predicted upper threshold is a constant.

[0140] As shown in Figure 15, multiple target sectors RSC (data area DTR) and multiple servo sectors SSC (servo area SV) are arranged in the circumferential direction. Each time the read head RHD passes through a servo sector SSC, the position of the head HD in the radial direction d1 can be corrected. This is an effective process when the head HD becomes oscillating due to the effects of seek operations, etc. However, the proportion (size) that the servo sector SSC occupies in the track STR is smaller than the proportion (size) that the target sector RSC occupies in the track STR. Therefore, it is difficult to sufficiently correct the position of the head HD in the radial direction d1.

[0141] Therefore, when write operations are performed on multiple target sectors RSC on the second track STR1, the positioning error PE may exceed the reference radius position PO multiple times. The correction limit prediction unit 66 calculates the cumulative predicted excess amount, while the management unit 68 predicts the number of damaged sectors CSC on the first track STR0. That is, each time the positioning error PE exceeds the reference radius position PO during the write period in which write operations are performed on the second track STR1, the management unit 68 detects that a damaged sector CSC has occurred on the first track STR0 and can manage the cumulative number of damaged sector CSCs on the first track STR0.

[0142] In the example in Figure 15, we focus on the point when the write processing unit 62 has performed write processing up to the nth target sector RSCn of the second track STR1. The management unit 68 can determine that 10 corrupted target sector CSCs have occurred on the first track STR0. Here, we assume that the error correction unit 64 can correct errors up to 12 corrupted target sector CSCs on the first track STR0. In that case, the determination unit 67 can determine that it can tolerate the occurrence of 10 corrupted target sector CSCs on the first track STR0, and can also tolerate the occurrence of up to 2 more new corrupted target sector CSCs.

[0143] Furthermore, the determination unit 67 can determine whether the cumulative predicted excess amount exceeds the prediction upper threshold. In the example in Figure 15, the first predicted excess amount and the first cumulative predicted excess amount correspond to the case where the seek distance is one track or less (Figure 14). For example, this is the case when a write operation to the second track STR1 is performed immediately after a write operation to the first track STR0. The first predicted excess amount becomes the minimum predicted excess amount, and the first cumulative predicted excess amount becomes the minimum cumulative predicted excess amount. Since the cumulative predicted excess amount is less than or equal to the prediction upper threshold, the determination unit 67 can determine that the write operation to the second track STR1 can be continued.

[0144] On the other hand, in the example in Figure 15, the second predicted excess and the second cumulative predicted excess correspond to the case where the seek distance is 2 tracks or more and the head HD shake is at its maximum (Figure 14). For example, this is the case when, after performing write processing up to the nth target sector RSCn of the second track STR1 during the first write period, a seek operation is performed, and then an attempt is made to resume write processing from the (n+1)th target sector RSC(n+1) of the second track STR1 during the second write period. The second predicted excess becomes the maximum predicted excess, and the second cumulative predicted excess becomes the maximum cumulative predicted excess. Since the cumulative predicted excess exceeds the prediction upper limit threshold, the determination unit 67 can determine that it is necessary to pause (or terminate) the write processing to the second track STR1.

[0145] (Examples of the second and third methods of the second light operation) (Predicted upper threshold: variable) Next, the second and third methods of the second write operation will be explained exemplified. Here, the predicted upper threshold will be treated as a variable. Figure 16 shows the change in positioning error PE, the change in cumulative excess amount, and the change in cumulative predicted excess amount when a write operation is performed on the second track STR1 using the second and third methods of the second write operation, and is a figure that shows the case when the predicted upper threshold is a variable.

[0146] As shown in Figure 16, first, we focus on the point when the write processing unit 62 has performed write processing up to the nth target sector RSCn of the second track STR1. The management unit 68 can determine that 10 corrupted target sector CSCs have occurred on the first track STR0. In that case, the determination unit 67 can determine that it can tolerate the occurrence of 10 corrupted target sector CSCs on the first track STR0, and can also tolerate the occurrence of up to 2 more new corrupted target sector CSCs.

[0147] Furthermore, the determination unit 67 can determine whether the cumulative predicted excess amount exceeds the prediction upper threshold. In the example in Figure 16, the first predicted excess amount corresponds to the case where the seek distance is one track or less (Figure 14). For example, this is the case when a write operation to the second track STR1 is performed immediately after a write operation to the first track STR0. The first predicted excess amount becomes the minimum predicted excess amount, and the prediction upper threshold becomes the maximum predicted upper threshold. Since the cumulative predicted excess amount is less than or equal to the prediction upper threshold, the determination unit 67 can determine that the write operation to the second track STR1 can be continued.

[0148] On the other hand, in the example in Figure 16, the second predicted excess corresponds to the case where the seek distance is two tracks or more and the head HD shake is at its maximum (Figure 14). For example, this occurs when, after performing write processing up to the nth target sector RSCn of the second track STR1 during the first write period, a seek operation is performed, and then an attempt is made to resume write processing from the (n+1)th target sector RSC(n+1) of the second track STR1 during the second write period. The second predicted excess becomes the maximum predicted excess, and the prediction upper limit threshold becomes the minimum prediction upper limit threshold. Since the cumulative predicted excess exceeds the prediction upper limit threshold, the determination unit 67 can determine that it is necessary to pause (or terminate) the write processing to the second track STR1.

[0149] Next, we will explain the results of the investigation into the number of PTS occurrences. Figure 17 is a bar graph showing the number of PTS occurrences (occurrence rate) when the magnetic disk drive 1 employs the first method of second write operation and the second method of second write operation. As shown in Figure 17, compared to the case where the first method of the second write operation is adopted, the second method of the second write operation does not make the cumulative predicted excess amount excessively large, so it can be seen that the frequency of pausing (or terminating) the write operation for the second track STR1 can be reduced. Since the second method of the second write operation can reduce the frequency of PTS activation, it can contribute to improving the write performance of the magnetic disk device 1. Although the bar graph for the third method of the second write operation is not shown, even in the third method of the second write operation, the frequency of PTS activation can be reduced, contributing to an improvement in the write performance of the magnetic disk drive 1.

[0150] Next, the first write operation will be explained illustratively using a flowchart. Figure 18 is a flowchart showing the write operation method for the nth target sector RSCn of the second track STR1 according to this embodiment, and is a diagram showing the case when the magnetic disk device 1 adopts the first write operation during the first write period. As shown in Figures 18, 1, and 12, when the first write operation is started, first, in step ST1a, the write processing unit 62 performs a write operation on the nth target sector RSCn of the second track STR1. Subsequently, in step ST2a, the correction limit prediction unit 66 determines whether the positioning error PE exceeds the reference radius position PO.

[0151] If the positioning error PE exceeds the reference radius position PO (step ST2a, YES), the process proceeds to step ST3a, and the light processing unit 62 pauses the light processing for the second track STR1. Then, in step ST4a, the light processing unit 62 starts the light retry process for the second track STR1. This completes the first light operation. On the other hand, if the positioning error PE is less than or equal to the reference radius position PO (step ST2a, NO), the process proceeds to step ST5a, and the light processing unit 62 continues the light processing for the second track STR1, ending the first light operation.

[0152] Next, a second method of the second write operation, in which the predicted upper threshold is treated as a constant, will be illustrated using a flowchart. Figure 19 is a flowchart showing the write processing method for the nth target sector RSCn of the second track STR1 according to this embodiment, and is a diagram showing the case when the magnetic disk device 1 adopts the second method of the second write operation during the first write period. Figure 20 is a flowchart of the write processing method following Figure 19.

[0153] As shown in Figures 19, 1, 12, and 15, when the second method of the second write operation, which treats the predicted upper limit threshold as a constant, is started, first in step ST1b, the write processing unit 62 performs a write operation on the nth target sector RSCn of the second track STR1. Subsequently, in step ST2b, the correction limit prediction unit 66 determines whether the positioning error PE exceeds the reference radius position PO.

[0154] If the positioning error PE exceeds the reference radius position PO (step ST2b, YES), the process moves to step ST3b, where the determination unit 67 determines whether the number of damaged sectors CSC on the first track STR0 exceeds the upper limit (e.g., 12). If the number of damaged sectors CSC on the first track STR0 exceeds the upper limit (step ST3b, YES), the process moves to step ST4b, where the write processing unit 62 terminates the write operation for the second track STR1, and in step ST5b, the magnetic disk device 1 activates PTS. This completes the second method of the second write operation.

[0155] On the other hand, if the positioning error PE is less than or equal to the reference radius position PO (step ST2b, NO), the process proceeds to step ST6b, and the light processing unit 62 continues the light processing for the second track STR1, ending the second method of the second light operation.

[0156] As shown in Figures 20, 1, 12, and 15, if the number of damaged sectors CSC on the first track STR0 is less than or equal to the upper limit (step ST3b, NO), the process proceeds to step ST7b, where the determination unit 67 determines whether the cumulative measured excess amount exceeds the predicted upper limit threshold. If the cumulative measured excess amount exceeds the predicted upper limit threshold (step ST7b, YES), the process proceeds to step ST4b in Figure 19.

[0157] On the other hand, if the cumulative measured excess is less than or equal to the predicted upper limit threshold (step ST7b, NO), the process moves to step ST8b, where the magnetic disk device 1 determines whether the first distance for moving the read head RHD is greater than or equal to the distance for moving it by two tracks. If the first distance is greater than or equal to the distance for moving it by two tracks (step ST8b, YES), the process moves to step ST9b, where the adjustment unit 65 calculates a second predicted excess that is greater than the first predicted excess (adjusting the first predicted excess to the second predicted excess), the correction limit prediction unit 66 adds the second predicted excess to the cumulative measured excess to calculate the second cumulative predicted excess (recalculation), and the process moves to step ST11b.

[0158] If the first distance is less than the distance to move by two tracks (step ST8b, NO), the process proceeds to step ST10b, where the correction limit prediction unit 66 maintains the calculated first cumulative predicted excess amount and proceeds to step ST11b. Next, in step ST11b, the determination unit 67 determines whether the first cumulative predicted excess amount (or the second cumulative predicted excess amount) has exceeded the prediction upper limit threshold.

[0159] If the first cumulative predicted excess amount (or the second cumulative predicted excess amount) is less than or equal to the prediction upper threshold (step ST11b, NO), the process proceeds to step ST6b in Figure 19. On the other hand, if the first cumulative predicted excess amount (or the second cumulative predicted excess amount) exceeds the prediction upper threshold (step ST11b, YES), the process proceeds to step ST4b in Figure 19.

[0160] Next, a third method of the second write operation, in which the predicted upper threshold is treated as a constant, will be illustrated using a flowchart. Figure 21 is a flowchart showing the write processing method for the nth target sector RSCn of the second track STR1 according to this embodiment, and is a diagram showing the case when the magnetic disk device 1 adopts the third method of the second write operation during the first write period and the second write period. Figure 22 is a flowchart of the write processing method following Figure 21. Figure 23 is a flowchart of the write processing method following Figure 22.

[0161] As shown in Figures 21, 1, 12, and 16, when the third method of the second write operation, which treats the predicted upper limit threshold as a constant, is started, first in step ST1c, the write processing unit 62 performs a write operation on the nth target sector RSCn of the second track STR1. Subsequently, in step ST2c, the correction limit prediction unit 66 determines whether the positioning error PE exceeds the reference radius position PO.

[0162] If the positioning error PE exceeds the reference radius position PO (step ST2c, YES), the process moves to step ST3c, where the determination unit 67 determines whether the number of damaged sectors CSC on the first track STR0 exceeds the upper limit (e.g., 12). If the number of damaged sectors CSC on the first track STR0 exceeds the upper limit (step ST3c, YES), the process moves to step ST4c, where the write processing unit 62 terminates the write operation for the second track STR1, and in step ST5c, the magnetic disk device 1 activates PTS. This completes the third method of the second write operation.

[0163] On the other hand, if the positioning error PE is less than or equal to the reference radius position PO (step ST2c, NO), the process proceeds to step ST6c, and the light processing unit 62 continues the light processing for the second track STR1, ending the third method of the second light operation.

[0164] As shown in Figures 22, 1, 12, and 16, if the number of damaged sectors CSC on the first track STR0 is less than or equal to the upper limit (step ST3c, NO), the process proceeds to step ST7c, where the determination unit 67 determines whether the cumulative measured excess amount exceeds the predicted upper limit threshold. If the cumulative measured excess amount exceeds the predicted upper limit threshold (step ST7c, YES), the process proceeds to step ST4c in Figure 21.

[0165] On the other hand, if the cumulative measured excess is less than or equal to the predicted upper limit threshold (step ST7c, NO), the process moves to step ST8c, where the magnetic disk device 1 determines whether the first distance for moving the read head RHD is greater than or equal to the distance for moving it by two tracks. If the first distance is less than the distance for moving it by two tracks (step ST8c, NO), the process moves to step ST10c, where the correction limit prediction unit 66 maintains the calculated first cumulative predicted excess and moves to step ST11c. Next, in step ST11c, the determination unit 67 determines whether the first cumulative predicted excess (or the second cumulative predicted excess) has exceeded the predicted upper limit threshold.

[0166] If the first cumulative predicted excess amount (or the second cumulative predicted excess amount) is less than or equal to the prediction upper threshold (step ST11c, NO), the process proceeds to step ST6c in Figure 21. On the other hand, if the first cumulative predicted excess amount (or the second cumulative predicted excess amount) exceeds the prediction upper threshold (step ST11c, YES), the process proceeds to step ST4c in Figure 21.

[0167] As shown in Figures 23, 1, 12, and 16, if the first distance is greater than or equal to the distance of moving two tracks (step ST8c, YES), the process proceeds to step ST9c, where the adjustment unit 65 calculates a second predicted excess amount that is greater than the first predicted excess amount (adjusting the first predicted excess amount to the second predicted excess amount), the correction limit prediction unit 66 adds the second predicted excess amount to the cumulative measured excess amount to calculate the second cumulative predicted excess amount (recalculation), and the process proceeds to step ST12c.

[0168] In step ST12c, the determination unit 67 determines whether the second cumulative predicted excess amount exceeds the prediction upper threshold. If the second cumulative predicted excess amount is less than or equal to the prediction upper threshold (step ST12c, NO), the process proceeds to step ST6c in Figure 21. On the other hand, if the second cumulative predicted excess amount exceeds the prediction upper threshold (step ST12c, YES), the process proceeds to step ST13c, and the write processing unit 62 pauses the write process for the second track STR1.

[0169] Subsequently, in step ST14c, the determination unit 67 performs a rotation waiting operation while the disk DK rotates once. Next, the process moves to step ST15c, where the adjustment unit 65 adjusts the second predicted excess amount to the minimum predicted excess amount, and the correction limit prediction unit 66 calculates the minimum cumulative predicted excess amount by adding the minimum predicted excess amount to the cumulative measured excess amount (recalculation), and then proceeds to step ST11c in Figure 22.

[0170] According to the magnetic disk device 1 of the first embodiment configured as described above, the magnetic disk device 1 comprises a disk DK, a head HD, a read processing unit 63, a write processing unit 62, an error correction unit 64, an adjustment unit 65, a correction limit prediction unit 66, and a determination unit 67. During the first write period, the read processing unit 63 executes a first seek process to seek the read head RHD, moving the read head RHD by a first distance and positioning the write head WHD opposite the second track STR1. The adjustment unit 65 derives a first predicted excess amount and a predicted upper limit threshold. The correction limit prediction unit 66 calculates a first cumulative predicted excess amount. If the determination unit 67 determines that the first cumulative predicted excess amount is less than or equal to the predicted upper limit threshold, it can allow the write processing unit 62 to continue writing to the second track STR1. If the determination unit 67 determines that the first cumulative predicted excess amount exceeds the predicted upper limit threshold, it can allow the write processing unit 62 to suspend writing to the second track STR1.

[0171] The adjustment unit 65 can adjust the predicted excess amount. By preventing the cumulative predicted excess amount from becoming excessively large, the frequency of pausing (or terminating) the write operation for the second track STR1 can be reduced. This reduces the frequency of PTS activation and contributes to improving the write performance of the magnetic disk device 1. From the above, it is possible to obtain a magnetic disk device 1 that can predict, in correspondence with the seek operation, whether or not the error correction on the track STR of disk DK will reach its limit.

[0172] Although the above embodiments of the present invention have been described, these embodiments are presented as examples only and are not intended to limit the scope of the invention. The above novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above embodiments and their variations are included in the scope and spirit of the invention, as well as in the claims of the invention and its equivalents. [Explanation of Symbols]

[0173] 1…Magnetic disk drive, 60…MPU, 61…Read / write processing unit, 62…Write processing unit, 63…Read processing unit, 64…Error correction unit, 65…Adjustment unit, 66…Correction limit prediction unit, 67…Decision unit, 68…Management unit, 70…Volatile memory, 80…Buffer memory, 90…Non-volatile memory, 100…Host, 110…System controller, 120…Driver IC, 130…Head amplifier IC, 140…R / W channel, 150…HDC, 24…V CM, 30...arm, DK...disk, L...recording layer, TR, STR, CTR...track, SC...sector, RSC...target sector, CSC...damaged target sector, HD...head, WHD...write head, RHD...read head, PE...positioning error, TM...track margin, PO...reference radius position, WOS...write-off track slice, d1...radial direction, d2...travel direction, d3...rotation direction, d5...overwriting direction, Da...first direction, Db...second direction.

Claims

1. A disk having a first data track and a second data track adjacent to each other on a recording layer, wherein the first data track and the second data track each include a plurality of target sectors on which data is to be written, and the first data track is located in a first direction parallel to the radial direction of the disk with respect to the second data track, A head having a write head for writing data to the recording layer and a read head for reading data from the recording layer, A read processing unit capable of performing a seek operation to seek the read head, A write processing unit capable of performing a write operation to write data to the recording layer, An error correction unit that performs error correction on the data of one or more corrupted target sectors of the plurality of target sectors of the first data track that are determined to have corrupted data, Adjustment section, Correction limit prediction unit, It comprises a determination unit, During the first write period, which is the period after the write processing unit has performed the write processing on the plurality of target sectors of the first data track and during the period in which the write processing is performed on the plurality of target sectors of the second data track, The read processing unit performs a first seek process to seek the read head, moves the read head by a first distance, and positions the write head opposite the second data track. The adjustment unit is, This is a first predicted excess amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction during the first light period, and the first predicted excess amount, which varies depending on the distance the read head seeks, is derived. This is a predictive upper limit threshold that indicates the limit of the range in which the error correction can be performed on the first data track, and the predictive upper limit threshold, which is a constant, is derived. The correction limit prediction unit measures the actual excess amount by which the position of the light head extends beyond the reference radius position in the first direction each time data is written to the target sector of the second data track, updates the cumulative actual excess amount which is the sum of the actual excess amounts, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount. The unit that makes the determination said, If it is determined that the first cumulative excess amount is less than or equal to the prediction upper threshold, the write processing unit is instructed to continue the write processing for the second data track. If it is determined that the first cumulative excess amount exceeds the prediction upper threshold, the write processing unit will suspend the write processing for the second data track. Magnetic disk drive.

2. The plurality of target sectors of the second data track include the nth target sector and the (n+1)th target sector following the nth target sector in the direction of head movement relative to the recording layer, During the first light period, The write processing unit executes the write process up to the nth target sector of the second data track. The correction limit prediction unit measures the actual excess amount, updates the cumulative actual excess amount, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount, the first predicted excess amount being the amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction, assuming that data is written to the (n+1)th target sector during the first write period. The unit that makes the determination said, If it is determined that the first cumulative predicted excess amount is less than or equal to the predicted upper threshold, the write processing unit is instructed to continue the write process for the (n+1)th target sector of the second data track. If it is determined that the first cumulative excess amount exceeds the prediction upper threshold, the write processing unit is instructed to pause the write operation for the (n+1)th target sector of the second data track. The magnetic disk device according to claim 1.

3. If the first distance is less than or equal to the distance required to move the read head by one data track in the radial direction, the adjustment unit adjusts the first predicted excess amount to the minimum predicted excess amount, If the first distance is greater than or equal to the distance required to move the read head by two data tracks in the radial direction, the adjustment unit adjusts the first predicted excess amount to an amount greater than the minimum predicted excess amount. The magnetic disk device according to claim 1.

4. During the first light period, The first distance by which the read processing unit moves the read head is greater than or equal to the distance by which it moves two data tracks, and The first predicted excess amount adjusted by the adjustment unit is greater than the minimum amount, and If the determination unit determines that the first cumulative excess amount exceeds the prediction upper threshold, The correction limit prediction unit further calculates the minimum cumulative predicted excess amount by adding the minimum predicted excess amount to the cumulative measured excess amount, The unit that makes the determination said, If it is determined that the minimum cumulative predicted excess amount is less than or equal to the predicted upper threshold, the drive of the write processing unit is controlled to pause the write processing for the second data track, maintain the position of the write head in the radial direction, wait for the disk to rotate, and then proceed to a write retry operation to resume the write processing. If it is determined that the minimum cumulative predicted excess amount exceeds the predicted upper threshold, the write processing unit is instructed to terminate the write process for the second data track, and the remaining data that could not be written to the second data track is saved to a recording area other than the first data track and the second data track. The magnetic disk device according to claim 3.

5. The plurality of target sectors of the second data track include the nth target sector and the (n+1)th target sector following the nth target sector in the direction of head movement relative to the recording layer, If the write operation is performed up to the nth target sector of the second data track during the first write period, and the read head is made to seek after the first write period, and then the write operation is resumed from the (n+1)th target sector of the second data track during the second write period, During the first light period, The write processing unit executes the write process up to the nth target sector of the second data track. The correction limit prediction unit measures the actual excess amount, updates the cumulative actual excess amount, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount, the first predicted excess amount being the amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction, assuming that data is written to the (n+1)th target sector during the first write period. During the aforementioned second light period, The read processing unit performs a second seek process to seek the read head, moves the read head by a second distance, and brings the write head to face the second data track again. The adjustment unit is a second predicted excess amount, which is the amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction during the second light period, and it re-derives the second predicted excess amount corresponding to the second distance. The correction limit prediction unit recalculates the second cumulative predicted excess amount by adding the second predicted excess amount to the cumulative actual excess amount, the second predicted excess amount being the amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction, assuming that data is written to the (n+1)th target sector during the second write period. The unit that makes the determination said, If it is determined that the second cumulative predicted excess amount is less than or equal to the predicted upper threshold, the write processing unit is instructed to resume the write process for the (n+1)th target sector of the second data track. If it is determined that the second cumulative predicted excess amount exceeds the predicted upper threshold, the write processing unit is instructed to pause the write process for the (n+1)th target sector of the second data track. The magnetic disk device according to claim 1.

6. The period during which the read processing unit performs the second seek processing includes an acceleration period, which is the first period, and a deceleration period, which is the last period. The lead processing unit is During the acceleration period, the read head is moved while gradually increasing the speed in the first seek direction. During the deceleration period, the read head is moved while gradually reducing the speed in the first seek direction. The magnetic disk device according to claim 5.

7. The writing unit is a tile-type recording unit that writes data from the second data track over the data from the first data track in a superimposing direction opposite to the first direction. The magnetic disk device according to claim 1.

8. A disk having a first data track and a second data track adjacent to each other on a recording layer, wherein the first data track and the second data track each include a plurality of target sectors on which data is to be written, and the first data track is located in a first direction parallel to the radial direction of the disk with respect to the second data track, A head having a write head for writing data to the recording layer and a read head for reading data from the recording layer, A read processing unit capable of performing a seek operation to seek the read head, A write processing unit capable of performing a write operation to write data to the recording layer, An error correction unit that performs error correction on the data of one or more corrupted target sectors of the plurality of target sectors of the first data track that are determined to have corrupted data, Adjustment section, Correction limit prediction unit, It comprises a determination unit, During the first write period, which is the period after the write processing unit has performed the write processing on the plurality of target sectors of the first data track and during the period in which the write processing is performed on the plurality of target sectors of the second data track, The read processing unit performs a first seek process to seek the read head, moves the read head by a first distance, and positions the write head opposite the second data track. The adjustment unit is, This is a first predicted excess amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction during the first light period, and the first predicted excess amount is derived which varies depending on the distance the read head seeks, and, A prediction upper limit threshold that indicates the limit of the range in which the error correction can be performed on the first data track, wherein the prediction upper limit threshold has a smaller value as each prediction excess amount, including the first prediction excess amount, increases, and the prediction upper limit threshold, which is a variable, is derived. The correction limit prediction unit measures the actual excess amount by which the position of the light head extends beyond the reference radius position in the first direction each time data is written to the target sector of the second data track, updates the cumulative actual excess amount which is the sum of the actual excess amounts, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount. The unit that makes the determination said, If it is determined that the first cumulative excess amount is less than or equal to the prediction upper threshold, the write processing unit is instructed to continue the write processing for the second data track. If it is determined that the first cumulative excess amount exceeds the prediction upper threshold, the write processing unit will suspend the write processing for the second data track. Magnetic disk drive.

9. The plurality of target sectors of the second data track include the nth target sector and the (n+1)th target sector following the nth target sector in the direction of head movement relative to the recording layer, During the first light period, The write processing unit executes the write process up to the nth target sector of the second data track. The correction limit prediction unit measures the actual excess amount, updates the cumulative actual excess amount, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount, the first predicted excess amount being the amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction, assuming that data is written to the (n+1)th target sector during the first write period. The unit that makes the determination said, If it is determined that the first cumulative predicted excess amount is less than or equal to the predicted upper threshold, the write processing unit is instructed to continue the write process for the (n+1)th target sector of the second data track. If it is determined that the first cumulative excess amount exceeds the prediction upper threshold, the write processing unit is instructed to pause the write operation for the (n+1)th target sector of the second data track. The magnetic disk device according to claim 8.

10. If the first distance is less than or equal to the distance required to move the read head by one data track in the radial direction, the adjustment unit adjusts the first predicted excess amount to the minimum predicted excess amount, and adjusts the predicted upper limit threshold to the maximum predicted upper limit threshold. If the first distance is greater than or equal to the distance required to move the read head by two data tracks in the radial direction, the adjustment unit adjusts the first predicted excess amount to an amount greater than the minimum predicted excess amount, and adjusts the predicted upper limit threshold to a value less than the maximum predicted upper limit threshold. The magnetic disk device according to claim 8.

11. During the first light period, The first distance by which the read processing unit moves the read head is greater than or equal to the distance by which it moves two data tracks, and The first predicted excess amount adjusted by the adjustment unit is greater than the minimum amount, and The prediction upper limit threshold adjusted by the adjustment unit is a value smaller than the maximum prediction upper limit threshold, and If the determination unit determines that the first cumulative excess amount exceeds the prediction upper threshold, The correction limit prediction unit further calculates the minimum cumulative predicted excess amount by adding the minimum predicted excess amount to the cumulative measured excess amount, The unit that makes the determination said, If it is determined that the minimum cumulative predicted excess amount is less than or equal to the predicted upper threshold, the drive of the write processing unit is controlled to pause the write processing for the second data track, maintain the position of the write head in the radial direction, wait for the disk to rotate, and then proceed to a write retry operation to resume the write processing. If it is determined that the minimum cumulative predicted excess amount exceeds the predicted upper threshold, the write processing unit is instructed to terminate the write process for the second data track, and the remaining data that could not be written to the second data track is saved to a recording area other than the first data track and the second data track. The magnetic disk device according to claim 10.

12. The plurality of target sectors of the second data track include the nth target sector and the (n+1)th target sector following the nth target sector in the direction of head movement relative to the recording layer, If the write operation is performed up to the nth target sector of the second data track during the first write period, and the read head is made to seek after the first write period, and then the write operation is resumed from the (n+1)th target sector of the second data track during the second write period, During the first light period, The write processing unit executes the write process up to the nth target sector of the second data track. The correction limit prediction unit measures the actual excess amount, updates the cumulative actual excess amount, and calculates the first cumulative predicted excess amount by adding the first predicted excess amount to the cumulative actual excess amount, the first predicted excess amount being the amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction, assuming that data is written to the (n+1)th target sector during the first write period. During the aforementioned second light period, The read processing unit performs a second seek process to seek the read head, moves the read head by a second distance, and brings the write head to face the second data track again. The adjustment unit is, This is a second predicted excess amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction during the second light period, and the second predicted excess amount corresponding to the second distance is re-derived, and, The aforementioned upper limit threshold for prediction is adjusted to a value corresponding to the second predicted excess amount. The correction limit prediction unit recalculates the second cumulative predicted excess amount by adding the second predicted excess amount to the cumulative actual excess amount, the second predicted excess amount being the amount by which the position of the light head is expected to extend beyond the reference radius position in the first direction, assuming that data is written to the (n+1)th target sector during the second write period. The unit that makes the determination said, If it is determined that the second cumulative predicted excess amount is less than or equal to the predicted upper threshold, the write processing unit is instructed to resume the write process for the (n+1)th target sector of the second data track. If it is determined that the second cumulative predicted excess amount exceeds the predicted upper threshold, the write processing unit is instructed to pause the write process for the (n+1)th target sector of the second data track. The magnetic disk device according to claim 8.

13. The period during which the read processing unit performs the second seek processing includes an acceleration period, which is the first period, and a deceleration period, which is the last period. The lead processing unit is During the acceleration period, the read head is moved while gradually increasing the speed in the first seek direction. During the deceleration period, the read head is moved while gradually reducing the speed in the first seek direction. The magnetic disk device according to claim 12.

14. The writing unit can select a writing format in which the data of the second data track is written on top of the data of the first data track in a writing direction opposite to the first direction. The magnetic disk device according to claim 8.

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