Magnetic disk device

Abstract

To provide a magnetic disk device capable of predicting whether error correction for a disk data track reaches its limit.SOLUTION: A magnetic disk device includes a disk DK, a write head WHD, a write processing unit 62, an error correction unit 64, an error limit prediction unit 65, and a determination unit 66. During a write period when a write operation is performed on a second data track, the error limit prediction unit 65 can determine whether the data of each target sector of a first data track is corrupted, and generates prediction information until the write operation is completed for all target sectors of the second track, and the determination unit 66 determines whether the write processing for the second data track is continued in the write processing unit 62 based on the prediction information.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-042888 [Patent Document 2] Japanese Patent Application Publication No. 2019-215943 [Patent Document 3] Patent Publication No. 2021-047946 Summary of the Invention [Problem to be solved by the invention]

[0004] This embodiment provides a magnetic disk drive that can predict whether error correction for a data track on the disk will reach its limit. [Means for solving the problem]

[0005] A magnetic disk device according to an embodiment includes: a disk having a first data track and a second data track adjacent to each other on a recording layer, the first data track and the second data track each including a plurality of target sectors to which data is to be written; a write head that writes data to the recording layer of the disc; a write processing unit capable of executing a write process for writing data to the recording layer; an error correction unit that performs error correction on data of a damaged target sector determined to have damaged data among the plurality of target sectors of each of the first data track and the second data track; a correction limit prediction unit; a determination unit, During a write period in which the write process is performed on the plurality of target sectors of the first data track and then the write process is performed on the plurality of target sectors of the second data track, The correction limit prediction unit It is possible to determine whether the data of the target sector of each of the first data tracks is corrupted; generating prediction information that predicts whether the error correction for the first data track will reach a limit before the write process for all target sectors of the second data track is completed; The determination unit determines whether to allow the write processing unit to continue the write process on the second data track based on the prediction information. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram showing the configuration of a magnetic disk device according to the first embodiment. [Figure 2] FIG. 2 is a perspective view showing a part of the magnetic disk device, showing a plurality of disks and a plurality of heads. [Figure 3] FIG. 3 is a schematic diagram showing an example of the arrangement of a plurality of servo areas and a plurality of data areas on one disk according to the embodiment. [Figure 4] FIG. 4 is a schematic diagram showing three tracks in the user data area of ​​the disk shown in FIG. 3 where shingled recording is performed, and a write head. [Figure 5] FIG. 5 is a schematic diagram showing three tracks of the media cache where normal recording processing of the disc shown in FIG. 3 is performed, and the write head. [Figure 6] FIG. 6 is a schematic diagram showing an example of a data write process on a disk. [Figure 7] FIG. 7 is a schematic diagram showing two bands and one guard band in the user data area shown in FIG. [Figure 8] FIG. 8 is a schematic diagram showing three sectors in one track of the band shown in FIG. [Figure 9] FIG. 9 is a schematic diagram showing the two bands and one guard band shown in FIG. 7, and is a diagram for explaining a plurality of target sectors and a plurality of unused sectors. [Figure 10] Figure 10 is a schematic diagram showing an example of the first track and the second track when it is assumed that the magnetic disk device does not have the function of performing error correction on track data on a track-by-track basis, a diagram for explaining the write process for the first track and the second track, a diagram for explaining the state in which the write process for the second track is continued until the error correction for the first track reaches its limit, and a diagram showing, in graph form, the change in BER for the first track and the change in BER with respect to the positioning error. [Figure 11]Figure 11 is a schematic diagram showing an example of the first track and the second track when it is assumed that the magnetic disk device does not have the function of performing track-by-track error correction on track data, a diagram for explaining the write processing for the first track and the second track, a diagram for explaining the state in which the judgment value is set to a write-off track slice that is smaller (stricter) than the track margin, and the write processing for the second track is terminated when it is detected that the positioning error has become equal to or greater than the write-off track slice, and a diagram showing graphs of the change in BER for the first track and the change in BER relative to the positioning error. [Figure 12] Figure 12 is a schematic diagram showing an example of the first track and second track of the above-mentioned magnetic disk device having the function of performing error correction on track data on a track-by-track basis, a diagram for explaining the write processing for the first track and the second track, a diagram for explaining a state in which the judgment value is set to a write-off track slice that is larger (loose) than the track margin, and the write processing for the second track is continued until the error correction for the first track reaches its limit, and a diagram showing graphs of the change in BER for the first track and the change in BER with respect to the positioning error. [Figure 13] Figure 13 is a schematic diagram showing an example of the first track and second track of the magnetic disk device having the function of performing error correction on track data on a track-by-track basis, and is a diagram for explaining the write processing on the first track and the second track, and is a diagram for explaining the state in which the write processing on the second track continues until the number of sectors on the first track that are subject to damage reaches five, and the write processing on the second track is terminated when the number reaches five. [Figure 14] FIG. 14 is a graph showing the change in the number of sectors to be damaged for the first track of FIG. [Figure 15]Figure 15 is a schematic diagram showing an example of the first track and second track of the magnetic disk device, and is a diagram for explaining the write processing for the first track and the second track. The write processing for the second track continues until the number of sectors to be damaged in the first track reaches three, and when the number reaches three, the prediction information regarding error correction changes to abnormal information, the write processing for the second track is paused, the error correction mode is switched to invalid mode, and the disk switches to an operation in which it waits for rotation. [Figure 16] Figure 16 is a graph showing the change in the number of sectors to be damaged for the first track in Figure 15, and is a diagram corresponding to the case where the prediction information is abnormal information, and also shows a timing chart regarding the positioning error, write gate, error correction mode valid flag, and rotation wait flag during the period when write processing is being performed on the second track. [Figure 17] Figure 17 is a diagram for explaining the above-mentioned write processing following Figure 15, and is a diagram for explaining the state in which, after the disk has gone through an operation of waiting for rotation and the predictive information regarding error correction has changed to normal information, the process transitions to a write retry operation in which the write processing for the second track is resumed. [Figure 18A] Figure 18A is a graph showing the change in the number of sectors that are subject to damage for the first track in Figure 17, where the predicted increase rate of sectors that are subject to damage is 1 / p2 and the prediction information is abnormal information, and also shows a timing chart for the positioning error, write gate, error correction mode valid flag, and rotation wait flag during the period when write processing is being performed on the second track. [Figure 18B] Figure 18B is a graph following Figure 18A showing the change in the number of sectors that are subject to damage for the first track, and corresponds to the case where the expected increase rate of sectors that are subject to damage is 1 / p3 and the prediction information is abnormal information.It also shows a timing chart for the positioning error, write gate, error correction mode valid flag, and rotation wait flag during the period when write processing is being performed on the second track. [Figure 18C] Figure 18C is a graph following Figure 18B showing the change in the number of sectors that are subject to damage for the first track, and corresponds to the case where the expected increase rate of sectors that are subject to damage is 1 / p4 and the prediction information is abnormal information.It also shows a timing chart for the positioning error, write gate, error correction mode valid flag, and rotation wait flag during the period when write processing is being performed on the second track. [Figure 18D] Figure 18D is a graph following Figure 18C showing the change in the number of sectors that are subject to damage for the first track, where the expected increase rate of sectors that are subject to damage is r / p5 and the prediction information is normal information, and also shows a timing chart for the positioning error, write gate, error correction mode valid flag, and rotation wait flag during the period when write processing is being performed on the second track. [Figure 19] FIG. 19 is a flowchart showing the write processing method according to the first embodiment. [Figure 20] FIG. 20 is a flowchart for explaining in detail some of the steps in the flowchart shown in FIG. [Figure 21] FIG. 21 is a diagram for explaining the write processing according to the first embodiment, and is a flowchart for explaining in detail another part of the steps in the flowchart shown in FIG. [Figure 22] FIG. 22 is a diagram for explaining the write processing according to the first embodiment, and is a flowchart for explaining in detail another part of the steps in the flowchart shown in FIG. [Figure 23] Figure 23 is a schematic diagram showing an example of the first track and the second track of a magnetic disk device according to the second embodiment, and is a diagram for explaining the write processing for the first track and the second track, in which the write processing for the second track is continued until the sum of the excess amounts related to the write head reaches or exceeds a second threshold, and the write processing for the second track is terminated when the sum reaches or exceeds the second threshold. [Figure 24] FIG. 24 is a graphical representation of the change in the sum for the first track of FIG. [Figure 25] FIG. 25 is a diagram for explaining the write processing according to the second embodiment, and is a flowchart for explaining in detail another part of the steps in the flowchart shown in FIG. [Figure 26] FIG. 26 is a diagram for explaining the write processing according to the second embodiment, and is a flowchart for explaining in detail another part of the steps in the flowchart shown in FIG. DETAILED DESCRIPTION OF THE INVENTION

[0007] (First embodiment) A magnetic disk device 1 according to a first embodiment will be described in detail below with reference to the drawings. First, the configuration of the magnetic disk device 1 will be described. FIG. 1 is a block diagram showing the configuration of the magnetic disk device 1 according to the first embodiment. In this embodiment, the magnetic disk device 1 is a hybrid recording type magnetic disk device that selectively executes a normal recording type and a shingled recording type. However, the techniques described below may be applied to a shingled recording type magnetic disk device or a normal recording type magnetic disk device.

[0008] 1, the magnetic disk device 1 includes a plurality of, for example, 1 to 10 disks (magnetic disks) DK as recording media, a spindle motor (SPM) 20 as a drive motor, a head stack assembly 22, a driver IC 120, a head amplifier integrated circuit (hereinafter referred to as head amplifier IC or preamplifier) ​​130, a volatile memory 70, a buffer memory (buffer) 80, a nonvolatile memory 90, and a system controller 110 which is a one-chip integrated circuit. The magnetic disk device 1 is also connected to a host system (hereinafter simply referred to as host) 100.

[0009] Each disk DK is formed to have a diameter of, for example, 97 mm (3.8 inches) and has a recording layer (magnetic recording layer) on both sides. In the first 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.

[0010] The head stack assembly 22 can control the movement of the head HD mounted on the arm 30 to a target position on the disk DK, i.e., can seek, by driving the voice coil motor (hereinafter referred to as VCM) 24. The VCM 24 functions as an actuator. The disk DK has a user data area U that can be used by the user and a system area S in which information required for system management is written, as areas where data can be written.

[0011] The head HD records and reproduces information on the disk DK. The head HD has a slider as its main body, and is equipped with a write head WHD and a read head RHD mounted on the slider. The write head WHD writes data to the recording layer of the disk DK. The read head RHD reads data from the data tracks on the recording layer of the disk DK.

[0012] The "center of the head HD" may be referred to as the "head HD", the "center of the write head WHD" may be referred to as the "write head WHD", and the "center of the read head RHD" may be referred to as the "read head RHD". The "center of the write head WHD" may be simply referred to as the "head HD", and the "center of the read head RHD" may be simply referred to as the "head HD".

[0013] The driver IC 120, under the control of the system controller 110 (more specifically, the MPU 60 described later), controls the driving of the SPM 20 and VCM 24. The SPM 20 supports and rotates a plurality of discs DK.

[0014] The head amplifier IC 130 includes a read amplifier and a write driver. The read amplifier amplifies a read signal read from the disk DK and outputs it to the system controller 110 (more specifically, to a read / write (R / W) channel 140, which will be described later). The write driver outputs a write current to the head HD according to the signal output from the R / W channel 140.

[0015] The volatile memory 70 is a semiconductor memory in which stored data is lost when the power supply is cut off. The volatile memory 70 stores data and the like required for processing in each section of the magnetic disk device 1. The volatile memory 70 is a random access memory (RAM). The volatile memory 70 is, for example, a dynamic random access memory (DRAM). However, the volatile memory 70 may also be a synchronous dynamic random access memory (SDRAM).

[0016] The buffer memory 80 is a semiconductor memory that temporarily records data and the like transmitted and received between the magnetic disk device 1 and the host 100. The buffer memory 80 may be configured integrally with the volatile memory 70. The buffer memory 80 is a volatile RAM. For example, the buffer memory 80 is a DRAM, an SRAM (Static Random Access Memory), an SDRAM, an FeRAM (Ferroelectric Random Access Memory), an MRAM (Magnetoresistive Random Access Memory), or the like. The buffer memory 80 includes an area used as a read cache and a write cache, and temporarily stores commands received from the host 100 .

[0017] The nonvolatile memory 90 is a semiconductor memory that records stored data even when the power supply is cut off. The nonvolatile memory 90 is, for example, a NAND-type flash read only memory (FROM). However, the nonvolatile memory 90 may also be a NOR-type FROM.

[0018] The system controller (controller) 110 is realized, for example, using a large-scale integrated circuit (LSI) called a system-on-a-chip (SoC), in which multiple elements are integrated on a single chip. The system controller 110 includes a read / write (R / W) channel 140, a hard disk controller (HDC) 150, and a microprocessor (MPU) 60. The system controller 110 is electrically connected to a driver IC 120, a head amplifier IC 130, a volatile memory 70, a buffer memory 80, a non-volatile memory 90, and a host 100.

[0019] The R / W channel 140 performs signal processing of read data transferred from the disk DK to the host 100 and write data transferred from the host 100 in response to instructions from the MPU 60 (described later). The R / W channel 140 has a circuit or function for modulating write data. The R / W channel 140 also has a circuit or function for measuring the signal quality of the read data. The R / W channel 140 is electrically connected to, for example, the head amplifier IC 130, the HDC 150, the MPU 60, etc.

[0020] The HDC 150 controls data transfer between the host 100 and the R / W channel 140 in response to instructions from the MPU 60, which will be described later. The HDC 150 is electrically connected to, for example, the R / W channel 140, the MPU 60, the volatile memory 70, the buffer memory 80, the non-volatile memory 90, and the like.

[0021] The HDC 150 has a gate generation unit 151. The gate generation unit 151 generates various gates, such as write gates, read gates, and servo gates, in response to commands from the host 100, instructions from the MPU 60, and the like, and outputs them to the R / W channel 140, for example, to the gate detection unit 141. Hereinafter, "raising a specific gate" may also be referred to as "asserting a specific gate." Also, "lowering a specific gate" may also be referred to as "negating a specific gate." "Asserting a specific gate" or "negating a specific gate" may also mean "generating a specific gate." The gate generation unit 151 may be included in the R / W channel 140 or the MPU 60.

[0022] The R / W channel 140 has a gate detection unit 141. The gate detection unit 141 detects whether various gates, such as a write gate, a read gate, and a servo gate, are in an asserted state or a negated state. For example, the gate detection unit 141 executes the write process when it detects that the write gate is asserted, and pauses (stops) the write process when it detects that the write gate is negated. In addition, the gate detector 141 executes a read process when it detects that the read gate is asserted, and stops the read process when it detects that the read gate is negated. The gate detector 141 executes a servo read process when it detects that the servo gate is asserted, and stops the servo read process when it detects that the servo gate is negated. The gate detector 141 may be located within the HDC 50 or the MPU 60.

[0023] The MPU 60 is a control unit and a main controller that controls each unit of the magnetic disk device 1. The MPU 60 controls the VCM 24 via the driver IC 120 and executes servo control to position the head HD. The MPU 60 controls the operation of writing data to the disk DK and selects a destination for write data transferred from the host 100. The MPU 60 also controls the operation of reading data from the disk DK and controls the processing of read data transferred from the disk DK to the host 100. The MPU 60 is connected to each unit of the magnetic disk device 1. The MPU 60 is electrically connected to, for example, the driver IC 120, the R / W channel 140, the HDC 150, etc.

[0024] The MPU 60 includes a read / write processing unit 61, an error correction unit 64, a correction limit prediction unit 65, a judgment unit 66, a switching unit 67, and a slip processing unit 68. The MPU 60 executes the processing of each of these units, such as the read / write processing unit 61, the error correction unit 64, the correction limit prediction unit 65, the judgment unit 66, the switching unit 67, and the slip processing unit 68, on firmware. Note that the MPU 60 may include each of these units as a circuit.

[0025] The read / write processing unit 61 has a write processing unit 62 and a read processing unit 63. In accordance with commands from the host 100, the write processing unit 62 controls data write processing, and the read processing unit 63 controls data read processing, causing the read head RHD to read data from the disk DK. The write processing unit 62 can execute write processing to write data to the recording layer of the disk DK. The read / write processing unit 61 controls the VCM 24 via the driver IC 120, positions the head HD to a target position (predetermined radial position) on the disk DK, and executes read processing or write processing.

[0026] FIG. 2 is a perspective view showing a part of the magnetic disk device 1, and shows a plurality of disks DK and a plurality of heads HD. As shown in Fig. 2, the direction in which the disk DK rotates in the circumferential direction is referred to as the rotation direction d3. Note that in the example shown in Fig. 2, the rotation direction is shown counterclockwise, but it may be the opposite (clockwise). Also, the moving direction d2 of the head HD relative to the disk DK is opposite to the rotation direction d3. The moving direction d2 is the direction in which the head HD sequentially writes and reads data to and from the disk DK in the circumferential direction, that is, the direction in which the head HD moves relative to the disk DK in the circumferential direction.

[0027] The magnetic disk device 1 includes i disks, disks DK1 to DKi, and j heads, heads HD1 to HDj. In this embodiment, the number of heads HD is twice the number of disks DK (j=2×i). The disks DK1 to DKi are arranged coaxially and stacked with a gap between them. The disks DK1 to DKi have the same diameter. Here, terms such as "same," "identical," "matched," and "equivalent" not only mean exactly the same, but also mean different enough to be considered substantially the same. The diameters of the disks DK1 to DKi may be different from each other.

[0028] Each disc DK has recording layers L on both sides. For example, disc DK1 has a first recording layer La1 and a second recording layer Lb1 opposite the first recording layer La1. Disc DK2 has a first recording layer La2 and a second recording layer Lb2 opposite the first recording layer La2. Disc DKi has a first recording layer Lai and a second recording layer Lbi opposite the first recording layer Lai. Each first recording layer La may also be referred to as a front surface or recording surface. Each second recording layer Lb may also be referred to as a back surface or recording surface. However, each first recording layer La may also be referred to as the back side, and in this case, each second recording layer Lb may also be referred to as the front side.

[0029] 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.

[0030] In the user data area Ua1 (first recording layer La1), the track sandwiched between the double dashed lines in the figure is called track Ta1. In the user data area Ub1 (second recording layer Lb1), the track located on the opposite side of track Ta1 is called track Tb1. In the user data area Ua2 (first recording layer La2), the track sandwiched between the double dashed lines in the figure is called track Tc1, and in the user data area Ub2 (second recording layer Lb2), the track located on the opposite side of track Tc1 is called track Td1. In the user data area Uai (first recording layer Lai), the track sandwiched between the double dashed lines in the figure is called track Te1. In the user data area Ubi (second recording layer Lbi), the track located on the opposite side of track Te1 is called track Tf1. In this embodiment, the tracks Ta1, Tb1, Tc1, Td1, Te1, and Tf1 are located on the same cylinder.

[0031] 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 the disk DK1, writes data to the first recording layer La1, and reads data from the first recording layer La1. Head HD2 faces the second recording layer Lb1 of the disk DK1, writes data to the second recording layer Lb1, and reads data from the second recording layer Lb1.

[0032] Head HD3 faces the first recording layer La2 of disk DK2 and writes data to and reads data from the first recording layer La2. Head HD4 faces the second recording layer Lb2 of disk DK2 and writes data to and reads data from the second recording layer Lb2. Head HDj-1 faces the first recording layer Lai of disk DKi and writes data to and reads data from the first recording layer Lai. Head HDj faces the second recording layer Lbi of disk DKi and writes data to and reads data from the second recording layer Lbi.

[0033] 3 is a schematic diagram showing an example of the arrangement of a plurality of servo areas SV and a plurality of data areas DTR on one disk DK according to the first embodiment. As shown in FIG. 3, in the radial direction d1 of the disk DK, the direction toward the outer periphery of the disk DK is referred to as the outward direction (outside), and the direction opposite to the outward direction is referred to as the inward direction (inside). In FIG. 3, the user data area U is divided into an inner area IR located inward, an outer area OR located outward, and a middle area MR located between the inner area IR and the outer area OR.

[0034] The disk DK has a plurality of servo areas SV and a plurality of data areas DTR. The plurality of servo areas SV may, for example, extend radially in the radial direction of the disk DK and be discretely arranged at predetermined intervals in the circumferential direction. The plurality of servo areas SV may, for example, extend linearly from the inner circumference to the outer circumference and be discretely arranged at predetermined intervals in the circumferential direction. The plurality of servo areas SV may, for example, extend spirally from the inner circumference to the outer circumference and be discretely arranged at predetermined intervals in the circumferential direction. Furthermore, the plurality of servo areas SV may, for example, be arranged in an island-like manner in the radial direction and be discretely arranged at predetermined intervals in the circumferential direction.

[0035] Hereinafter, one servo area SV in a given track may be referred to as a "servo sector." Note that a "servo area SV" may also be referred to as a "servo sector SV." A servo sector contains servo data. Hereinafter, "the arrangement of several servo data that make up a servo sector" may also be referred to as a "servo pattern." Note that "servo data written in a servo sector" may also be referred to as a "servo sector."

[0036] Each of the multiple data areas DTR is disposed between multiple servo areas SV. For example, a data area DTR corresponds to an area between two consecutive servo areas SV in the circumferential direction. Hereinafter, one data area DTR in a given track may be referred to as a "data sector." Note that a "data area DTR" may also be referred to as a "data sector DTR." A data sector contains user data. Note that "user data written to a data sector" may also be referred to as a "data sector." A "data sector" may also be referred to as "user data." Also, a "pattern composed of several pieces of data" may also be referred to as a "data pattern." In the example shown in FIG. 3, the data pattern of a given track is composed of multiple servo data (servo sectors) and multiple user data (data sectors).

[0037] The servo area SV has a plurality of zone servo areas ZSV, etc. In addition to the zone servo areas ZSV, the servo area SV may also include an area including a gap (a deviation in the circumferential position of two zone servo areas), an area including servo data, and a data area DTR, etc. The plurality of zone servo areas ZSV are discretely arranged along the radial direction d1. Each of the plurality of zone servo areas ZSV extends in the radial direction d1.

[0038] One zone servo area (servo area) ZSV in a specified track may be referred to as a "zone servo sector" or "servo sector." Note that a "zone servo area (servo area) ZSV" may also be referred to as a "zone servo sector ZSV" or "servo sector ZSV." "Servo data written in a zone servo sector" may also be referred to as a "zone servo sector" or "servo sector." Hereinafter, "the arrangement of several servo data constituting a zone servo sector" may also be referred to as a "zone servo pattern" or "servo pattern." Hereinafter, one servo area SV in a specified track may also be referred to as a "zone pattern sector."

[0039] Note that a "servo area SV" may also be referred to as a "zone pattern sector." "At least one piece of data, etc. written to a zone pattern sector" may also be referred to as a "zone pattern sector." A zone pattern sector includes at least one zone servo sector. Hereinafter, "data pattern of a zone pattern sector" may also be referred to as a "zone data pattern."

[0040] 3, the servo area SV has zone servo areas ZSV0, ZSV1, and ZSV2. The zone servo areas ZSV0, ZSV1, and ZSV2 are arranged in a staggered pattern in the radial direction. The zone servo areas ZSV0, ZSV1, and ZSV2 may also be arranged in a stepped pattern in the radial direction.

[0041] Zone servo area ZSV2 is located closer to the inner periphery than zone servo area ZSV1. Zone servo area ZSV0 is located closer to the outer periphery than zone servo area ZSV1. For example, zone servo area ZSV2 is arranged from inner area IR to middle area MR, zone servo area ZSV1 is arranged from inner area IR to outer area OR, and zone servo area ZSV0 is arranged from middle area MR to outer area OR. Hereinafter, in a given servo area SV, a given radial area in which multiple zone servo areas ZSV are arranged in the circumferential direction may also be referred to as a zone servo boundary area, a double servo area, or a double zone servo area ZB.

[0042] In the example shown in Fig. 3, the primary servo areas SVO and the secondary servo areas SVE are alternately arranged at intervals in the circumferential direction. For example, one secondary servo area SVE is arranged between two primary servo areas SVO that are consecutively arranged at an interval in the circumferential direction. In other words, one secondary servo area SVE is arranged between two primary servo areas SVO that are consecutively arranged at an interval in the circumferential direction. For example, if consecutive numbers are assigned to all the servo areas SV of the disk DK in order, the primary servo areas SVO correspond to the odd-numbered servo areas SV, and the secondary servo areas SVE correspond to the even-numbered servo areas SV. Note that two or more secondary servo areas SVE may be arranged between two primary servo areas SVO that are consecutively arranged at an interval in the circumferential direction.

[0043] The primary servo area SVO and the secondary servo area SVE may be, for example, composed only of a servo area (hereinafter sometimes referred to as a normal servo area) that reads and demodulates servo data as a whole. Hereinafter, "reading and demodulating servo data" may also be referred to as "servo reading." The primary servo area SVO and the secondary servo area SVE may be, for example, composed of a normal servo area and a servo area (hereinafter sometimes referred to as a short servo area) that servo reads a circumferential range of servo data that is smaller than the circumferential range of servo data servo read in the normal servo area.

[0044] The media cache M is allocated to the disk DK. However, the media cache M does not have to be located on the disk DK. By using the above-mentioned plurality of servo data, for example, it is possible to derive the positioning error of the head HD (for example, the write head WHD).

[0045] In the explanation of the first embodiment, the disk DK has three zones, but the number of zones on the disk DK can be changed in various ways. The number of zones on the disk DK may be 30 to 40. Furthermore, each zone has multiple bands. For example, each zone may have several hundred bands.

[0046] 4 is a schematic diagram showing the write head WHD and three tracks STR in the user data area U where shingled recording is performed on the disk DK shown in FIG. 3. The user data area U is a shingled recording area. Within the user data area U, it is permitted to write data sequentially in band units, that is, shingled recording is permitted.

[0047] As shown in Fig. 4, the write head WHD can sequentially write data to the disk DK in the travel direction d2. The read head RHD shown in Fig. 3 can also sequentially read data written to the disk DK in the travel direction d2.

[0048] The direction in which a plurality of tracks STR, which are a plurality of data tracks, are continuously shingled-recorded in a direction parallel to the radial direction d1, that is, the direction in which the next track STR to be written is overlapped on the track STR written one before in the radial direction d1, is called the overwrite direction or recording progress direction. In the band BAe shown in Figure 4, the overwrite direction d5 is an inward direction, but the overwrite direction may also be an outward direction. For example, the overwrite direction applied to multiple bands BA (multiple zones Z) located on the outer side of a specific radial position may be opposite to the overwrite direction applied to multiple bands BA (multiple zones Z) located on the inner side of the specific radial position.

[0049] Band BAe has a plurality of tracks STR, including tracks STRe, STRe+1, and STRe+2. Tracks STRe, STRe+1, and STRe+2 are continuously overwritten in the order shown in the overwrite direction d5. Of tracks STRe, STRe+1, and STRe+2, track STRe corresponds to the track onto which data is written first, and track STRe+2 corresponds to the track onto which data is written last.

[0050] Track STRe has a track center STCe at the center in the radial direction d1 when no other tracks have been overwritten. Track STRe+1 has a track center STCe+1 at the center in the radial direction d1 when no other tracks have been overwritten. Track STRe+2 has a track center STCe+2 at the center in the radial direction d1 when no other tracks have been overwritten.

[0051] In the example shown in Figure 4, tracks STRe, STRe+1, and STRe+2 are written at a pitch (shingled recording track pitch) STP. The track center STCe of track STRe and the track center STCe+1 of track STRe+1 are spaced apart in the radial direction d1 by a pitch STP. The track center STCe+1 of track STRe+1 and the track center STCe+2 of track STRe+2 are spaced apart in the radial direction d1 by a pitch STP. Tracks STRe to STRe+2 may be written at different pitches.

[0052] The width in the radial direction d1 of the area of ​​track STRe where track STRe+1 is not overwritten is the same as the width in the radial direction d1 of the area of ​​track STRe+1 where track STRe+2 is not overwritten. Note that the width in the radial direction d1 of the area of ​​track STRe where track STRe+1 is not overwritten may be different from the width in the radial direction d1 of the area of ​​track STRe+1 where track STRe+2 is not overwritten.

[0053] In Fig. 4, for convenience of explanation, each track STR is shown as a rectangle, but in reality, each track STR is curved along the circumferential direction. Also, each track STR may be wavy, extending in the circumferential direction while fluctuating in the radial direction d1. Note that in Fig. 4, three tracks STR are overwritten, but two tracks STR may be overwritten, or more than three tracks STR may be overwritten.

[0054] The write processing unit 62 selects a shingled recording format in which data is written to multiple tracks STR in an overwrite direction d5, and causes the write head WHD to write data to each band BA. In the example shown in Fig. 4, the write processing unit 62 sequentially shingles data on tracks STRe to STRe+2 in band BAe inward (overwrite direction d5) at a pitch STP. Since data is written to the user data area U using the shingled recording format, the recording density of the user data area U can be improved.

[0055] The write processing unit 62 writes track STRe+1 inward from track STRe at pitch STP, and overwrites track STRe+1 on a part of the inner circumference side of track STRe. The write processing unit 62 writes track STRe+2 inward from track STRe+1 at pitch STP, and overwrites track STRe+2 on a part of the inner circumference side of track STRe+1.

[0056] Figure 5 is a schematic diagram showing the three tracks CTR and the write head WHD of the media cache M where normal recording processing of the disk DK shown in Figure 3 is performed. The media cache M and the system area S shown in Figure 3 are normal recording areas. Random data writing is permitted in the media cache M and the system area S, that is, normal recording is permitted.

[0057] 5, the media cache M has a plurality of tracks CTR including tracks CTRe, CTRe+1, and CTRe+2. Each of the plurality of tracks CTR is a data track. For example, the width in the radial direction d1 (track width) of the tracks CTRe, CTRe+1, and CTRe+2 is the same. Note that the track widths of the tracks CTRe to CTRe+2 may be different from each other.

[0058] Track CTRe has a track center CTCe at the center in the radial direction d1, track CTRe+1 has a track center CTCe+1 at the center in the radial direction d1, and track CTRe+2 has a track center CTCe+2 at the center in the radial direction d1. In the example shown in Fig. 5, tracks CTRe, CTRe+1, and CTRe+2 are written at a pitch (normal recording track pitch) CTP. The track center CTCe of track CTRe and the track center CTCe+1 of track CTRe+1 are separated by the pitch CTP. The track center CTCe+1 of track CTRe+1 and the track center CTCe+2 of track CTRe+2 are separated by the pitch CTP.

[0059] The tracks CTRe and CTRe+1 are separated by a gap GP. The tracks CTRe+1 and CTRe+2 are separated by a gap GP. The tracks CTRe to CTRe+2 may be written at different pitches. For ease of explanation, each track CTR is shown as a rectangle in FIG. 5, but in reality, each track CTR is curved along the circumferential direction. Furthermore, each track CTR may be wavy, extending in the circumferential direction while fluctuating in the radial direction d1.

[0060] The write processing unit 62 can select a normal recording format in which data is written to a plurality of tracks CTR at intervals in the radial direction d1 of the disk DK and perform the write processing. In the example shown in Figure 5, the write processing unit 62 positions the write head WHD at the track center CTCe in a predetermined area of ​​the disk DK and performs normal recording on the track CTRe or a predetermined sector of the track CTRe.

[0061] The write processing unit 62 positions the write head WHD at a track center CTCe+1 that is spaced inward from the track center CTCe of the track CTRe by the pitch CTP, and performs normal recording on the track CTRe+1 or a predetermined sector of the track CTRe+1. The write processing unit 62 positions the write head WHD at a track center CTCe+2 that is spaced inward from the track center CTCe+1 of the track CTRe+1 by the pitch CTP, and performs normal recording on the track CTRe+2 or a predetermined sector of the track CTRe+2.

[0062] The write processing unit 62 may normally record tracks CTRe, CTRe+1, and CTRe+2 sequentially in a predetermined area of ​​the disk DK, or may normally record randomly in a predetermined sector of track CTRe, a predetermined sector of track CTRe+1, and a predetermined sector of track CTRe+2.

[0063] 6 is a schematic diagram showing an example of data write processing on a disk DK. Tracks STR and CTR are data tracks. As shown in FIG. 6, the user data area U has bands BAa, BAb, and BAc. Bands BAa, BAb, and BAc belong to the same zone Ze. In zone Ze, bands BAa, BAb, and BAc are arranged intermittently in the overwrite direction in the order in which they are written.

[0064] Bands BAa and BAb are adjacent to each other in the radial direction d1, and bands BAb and BAc are adjacent to each other in the radial direction d1. Band BAa includes x tracks: STRa0, STRa1, STRa2, ..., STRa(x-3), STRa(x-2), and STRa(x-1). Tracks STRa0 to STRa(x-1) are shingled recorded in the order listed in the overwrite direction d5. In band BAa, track STRa0 corresponds to the first track onto which data is written first, and track STRa(x-1) corresponds to the last track onto which data is written last.

[0065] Band BAb includes x tracks: STRb0, STRb1, STRb2, ..., STRb(x-3), STRb(x-2), and STRb(x-1). Tracks STRb0 to STRb(x-1) are shingled recorded in the order listed in the overwrite direction d5. In band BAb, track STRb0 corresponds to the first track onto which data is written first, and track STRb(x-1) corresponds to the last track onto which data is written last.

[0066] Band BAc includes x tracks: STRc0, STRc1, STRc2, ..., STRc(x-3), STRc(x-2), and STRc(x-1). Tracks STRc0 to STRc(x-1) are shingled recorded in the order listed in the overwrite direction d5. In band BAc, track STRc0 corresponds to the first track onto which data is written first, and track STRc(x-1) corresponds to the last track onto which data is written last.

[0067] Each band BA belonging to the same zone Z has the same number of tracks STR. For example, each band BA belonging to zone Ze has the same number of tracks STR. In other words, the number of tracks STR that a band BA has is fixed for each zone Z. In this example, the number of tracks STR that each band BA belonging to zone Ze has is x.

[0068] Fig. 6 shows tracks CTR(x-2) and CTR(x-1). In Fig. 6, tracks CTR(x-2) and CTR(x-1) are usually recorded in the media cache M or the system area S. Tracks CTR(x-2) and CTR(x-1) are adjacent to each other in the radial direction d1.

[0069] Fig. 7 is a schematic diagram showing two bands BAa and BAb and one guard band GB in the user data area U shown in Fig. 6. As shown in Fig. 7, the shingled recording method differs from the normal recording method in that part of the track STR is overwritten, and therefore the MPU 60 manages the track group in the user data area U in units called bands.

[0070] A guard band GB is generally provided between bands BA adjacent in the radial direction d1. The guard band GB includes a guard track GTR. Unlike the first embodiment, the guard band GB may include multiple guard tracks GTR. The guard band GB has the role of suppressing interference between adjacent bands BA. The guard band GB makes it possible to perform shingled recording in units of one band BA. Furthermore, the guard band GB makes it possible to separate the ranges (bands BA) to be written sequentially.

[0071] For example, the track center STCa(x-3) of track STRa(x-3), the track center STCa(x-2) of track STRa(x-2), the track center STCa(x-1) of track STRa(x-1), the track center GTC of the guard track GTR, the track center STCb0 of track STRb0, the track center STCb1 of track STRb1, and the track center STCb2 of track STRb2 are positioned at equal pitches in the overwrite direction d5.

[0072] Excluding 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 required specifications. The MPU 60 can record the same amount of data in each band BA. Typically, the recording capacity of each band BA is 128 MiB or 256 MiB.

[0073] 8 is a schematic diagram showing three sectors SCe, SC(e+1), and SC(e+2) of one track STRa0 of band BAa shown in FIG. 6. As shown in FIG. 8, each track STR has a plurality of sectors SC. Track STRa1 has a plurality of sectors SC including sectors SCe, SC(e+1), and SC(e+2). Each track STR belonging to the same zone Z has the same number of sectors SC. In this first embodiment, each track STR belonging to zone Ze has y sectors SC.

[0074] Each sector SC has a length Ls in the circumferential direction of the disk DK. Each sector SC may be a split sector separated by a servo sector SV. In this case, the length of the sector SC does not have to be Ls. The write head WHD is a magnetic head for energy-assisted recording (EAMR) that performs energy-assisted magnetic recording. In the first embodiment, the write head WHD is configured to use energy other than magnetic energy, but the write head WHD is not limited to this and may be a magnetic head that is not configured to perform energy-assisted recording.

[0075] FIG. 9 is a schematic diagram showing the two bands BAa and BAb and one guard band GB shown in FIG. 7, and is a diagram for explaining a plurality of target sectors RSC and a plurality of unused sectors VSC. In Fig. 9, for convenience of explanation, each track STR is shown as a rectangle, but in reality, each track STR is curved along the circumferential direction. Furthermore, although multiple tracks STR are arranged in the overwrite direction d5 without overlapping, in reality, multiple tracks STR are arranged in the overwrite direction d5 while overlapping. Furthermore, in the figure, target sectors RSC are marked with a dot pattern. Unused sectors VSC are shown as plain.

[0076] As shown in Figure 9, the band number of band BAa is "a" and the band number of band BAb is "b". The track numbers of each band BA are "0" to "x-1". The sector numbers of each track STR are "0" to "y-1". Hereinafter, sector SC of each band BA may be identified using the following symbol: "SC (track number, sector number)".

[0077] In the first embodiment, band BAa is a band adjacent to band BAb, and is a band located to the right of band BAb in the overwriting direction d5. Each track STR in band BAa contains G target sectors RSC (one or more target sectors RSC) in which valid data is written. For example, track STRa0 has y target sectors RSC (G=y). All sectors SC in track STRa0 are target sectors RSC. Track STRa(x-1) has five target sectors RSC (G=5). The remaining sectors SC in track STRa(x-1) are unused sectors VSC in which valid data is not written. From the above, the number of target sectors RSC in track STRa0 is different from the number of target sectors RSC in track STRa(x-1).

[0078] In each band BA of zone Ze, all sectors SC in x-1 tracks STR numbered 0 to x-2 are target sectors RSC in which valid data is written and are recording sectors USC. In the x-1 track STR of each band BA of zone Ze, five sectors SC numbered 0 to 4 are target sectors RSC and are recording sectors USC. Meanwhile, in the x-1 track STR, the remaining sectors SC numbered 5 to y-1 are unused sectors VSC in which valid data is not written.

[0079] 10 is a schematic diagram showing an example of the first track STR0 and the second track STR1 when it is assumed that the magnetic disk device 1 does not have a function for performing error correction on the data of the track TR, a diagram for explaining the write process on the first track STR0 and the second track STR1, a diagram for explaining a state in which the write process on the second track STR1 is continued until the error correction on the first track STR0 reaches its limit, and a graph showing the change in the bit error rate (BER) for the first track STR0 and the change in the BER relative to the positioning error (PE). In the explanation using FIG. 10, the magnetic disk device 1 will be described as not having the error correction unit 64 of FIG. 1. Also, in FIG. 10, for convenience of explanation, the first track STR0, etc. are drawn as if the circumferential direction is linear.

[0080] 10, 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. The write process for the first track STR0 is ideally performed without a positioning error PE (PE≈0, or PE=0).

[0081] If the magnetic disk drive 1 is affected by external vibrations or the like during a 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 its target position in the radial direction d1. By setting the track margin TM, it is possible to determine the tolerance range within which it is guaranteed that data on adjacent tracks can be read.

[0082] For example, when a write operation is performed on the second track STR1, if the target sectors RSCe, RSC(e+1), and RSC(e+2) of the first track STR0 are adjacent to the write head WHD in the radial direction d1 during a period in which the positioning error PE exceeds the track margin TM, the data in the target sectors RSCe, RSC(e+1), and RSC(e+2) of the first track STR0 are determined to be corrupted. While a lower data BER is desirable, the BER of the data in the 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). The BER of the data in the first track STR0, which is excessively affected by ATI, becomes excessively high.

[0083] Therefore, among the multiple target sectors RSC in the first track STR0, target sectors RSCe, RSC(e+1), and RSC(e+2) are determined to be damage target sectors CSC1, CSC2, and CSC3, respectively, which may result in a deterioration in the quality of the signal obtained by reading the data from the damage target sectors CSC1 to CSC3, or in the erasure of the data from the damage target sectors CSC1 to CSC3.

[0084] 10, the magnetic disk device 1 does not have a function for performing track-by-track error correction on the data of the track TR. Here, the track-by-track error correction is also called track error correction, track ECC (Error Checking and Correcting), etc. Therefore, the target sector RSCe, the target sector RSC(e+1), and the target sector RSC(e+2) remain as damaged target sector CSC1, the damaged target sector CSC2, and the damaged target sector CSC3.

[0085] 10, it has been explained that all target sectors RSC of the track TR have a common track margin TM. In the explanations of Figures 11, 12, 13, 15, 17, and 23 described later, it is also explained that all target sectors RSC of the track TR have a common track margin TM. However, the setting of the track margin TM above is just an example, and the track margin TM may be different for each target sector RSC.

[0086] 11 is a schematic diagram showing an example of the first track STR0 and the second track STR1 when it is assumed that the magnetic disk device 1 does not have a function for performing track-by-track error correction on data in the track TR. It is also a diagram for explaining the write process for the first track STR0 and the second track STR1. It is also a diagram for explaining a state in which the judgment value is set to a write-off-track slice WOS smaller (stricter) than the track margin TM, and the write process for the second track STR1 is paused when it is detected that the positioning error PE is equal to or greater than the write-off-track slice WOS. It is also a graph showing the change in BER for the first track STR0 and the change in BER relative to the positioning error PE. For ease of explanation, the first track STR0, etc. are also depicted as being linear in the circumferential direction in FIG. 11. In the explanation using FIG. 11, the magnetic disk device 1 will be described as not including the error correction unit 64 of FIG. 1.

[0087] 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. The write process for the first track STR0 is ideally performed without a positioning error PE (PE≈0, or PE=0).

[0088] To prevent or suppress the write process in a state where the positioning error PE exceeds the track margin TM, the magnetic disk device 1 has a write off-track slice WOS. During the period of writing data to the second track STR1, when it is determined that the positioning error PE exceeds the write off-track slice WOS, 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.

[0089] Note that the track STR has servo sectors in addition to the sector SC which is a data sector. In the track STR, generally, data sectors and servo sectors are arranged alternately. The write head WHD can derive the positioning error PE together with the servo sectors. Therefore, generally, the positioning error PE is information obtained intermittently.

[0090] In order not to have PE > TM, it is necessary to set the write off-track slice WOS such that WOS ≤ TM. To avoid a situation where PE > TM, it is desirable to set the write off-track slice WOS such 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.

[0091] However, it should be noted that the smaller the write-off track slice WOS is set, the more likely the write process will be paused, resulting in a degradation of the write performance of the magnetic disk device 1. In a magnetic disk device 1 that does not have the function of performing error correction on a track-by-track basis, if the write process to the second track STR1 is paused, a write retry process is executed to wait for the disk DK to rotate until PE≦WOS and then resume the write process to the second track STR1. In the write retry process, the empty sectors ESC of the second track STR1 can be changed to recording sectors USC, thereby avoiding a situation in which the utilization efficiency of the second track STR1 remains low.

[0092] 11, it is assumed that all target sectors RSC of the track TR have a common write-off track slice WOS. In the explanation of FIG. 12 described later, it is also assumed that all target sectors RSC of the track TR have a common write-off track slice WOS. However, the setting of the write-off track slice WOS described above is just an example, and the write-off track slice WOS may be different for each target sector RSC.

[0093] 12 is a schematic diagram showing an example of a first track STR0 and a second track STR1 of a magnetic disk device 1 having a function of performing error correction on data of a track TR on a track-by-track basis, a diagram for explaining the write processing for the first track STR0 and the second track STR1, a diagram for explaining a state in which a judgment value is set to a write-off track slice WOS larger (loose) than the track margin TM, and the write processing for the second track STR1 is continued until the error correction for the first track STR0 reaches its limit, and a diagram showing, in graphs, the change in BER for the first track STR0 and the change in BER with respect to the positioning error PE. For convenience of explanation, in FIG. 12, the first track STR0, etc. are also drawn as if the circumferential direction were linear.

[0094] As shown in FIG. 12, the write process for the first track STR0 is ideally performed without a positioning error PE (PE≈0, or PE=0). The magnetic disk device 1 includes an error correction unit 64. When a damaged sector CSC occurs in the track ST, the read processing unit 63, together with the head amplifier IC 130, can detect that the damaged sector CSC has occurred in the track ST, and the error correction unit 64 can execute an error correction process to recover the data in the damaged sector CSC. For example, when a damaged sector CSC occurs in the first track STR0, the error correction unit 64 recovers the data in the damaged sector CSC based on the data in the multiple target sectors RSC in the first track STR0 and the data in the parity sector.

[0095] The parity sector is generated based on the data of a plurality of target sectors RSC in the first track STR0, and can be provided in a part of the plurality of target sectors RSC in the first track STR0. However, the parity sector may be provided in a track TR other than the first track STR0. Alternatively, the parity sector may be provided in a memory other than a disk (for example, the non-volatile memory 90).

[0096] As described above, even if a damage-target sector CSC occurs in the first track STR0, the error correction unit 64 can execute error correction processing to recover the data in the damage-target sector CSC, so that the occurrence of the damage-target sector CSC in the first track STR0 can be tolerated. In the magnetic disk device 1 equipped with the error correction unit 64, the write-off track slice WOS can be set so that WOS≧TM, making it difficult for the write process to be terminated and suppressing a deterioration in the write performance of the magnetic disk device 1.

[0097] It should be noted that there is an upper limit in units of tracks TR for the number of damage-target sectors for which the error correction unit 64 can perform error correction in units of tracks. For example, if the number of damage-target sectors CSC in the first track STR0 exceeds the upper limit (for example, five), the error correction unit 64 can recover the data of the five damage-target sectors CSC, but it becomes difficult to recover the data of the sixth and subsequent damage-target sectors CSC.

[0098] 13 is a schematic diagram showing an example of a first track STR0 and a second track STR1 of a magnetic disk device 1 having a function for performing track-by-track error correction on data in a track TR, and is a diagram for explaining write processing for the first track STR0 and the second track STR1, and is a diagram for explaining a state in which write processing for the second track STR1 continues until the number of damage-target sectors CSC in the first track STR0 reaches five, and then ends when the number reaches five. For ease of explanation, in FIG. 13, the first track STR0, etc. are also depicted as if the circumferential direction were linear. FIG. 14 is a graph showing the change in the number of damage-target sectors CSC for the first track STR0 of FIG. 13.

[0099] As shown in FIGS. 13 and 14, the write process for the first track STR0 is ideally performed without a positioning error PE (PE≈0, or PE=0). As described above, the number of damage target sectors for which the error correction unit 64 can perform error correction on a track-by-track basis is limited. If PE>TM occurs frequently, the number of damage target sectors CSC in the adjacent tracks TR increases, and there is a concern that error correction will not be possible for all of the damage target sectors CSC.

[0100] To address this issue, a technology has been disclosed that determines whether the track ECC correction limit has been reached based on the relationship between the positioning error PE during write processing and the track margin TM, and the number of data sectors determined to have been interfered with in adjacent tracks and the degree of interference (JP 2023-119547 A). According to this disclosed technology, when it is determined that the track ECC correction limit has been reached, the write operation is stopped and the remaining data is slipped to an adjacent track or another area (see paragraphs 0078-0080 of the specification, Figure 11 of the drawings, etc.).

[0101] The first threshold H1 is the upper limit of the number of damage-target sectors CSC in each track TR for which the error correction unit 64 can perform error correction on a track-by-track basis. Here, an example is shown in which the first threshold H1 is set to 5 sectors (H1=5). During the write process for the second track STR1, the magnetic disk device 1 enters a vibration state, and the number of damage-target sectors CSC occurring in the first track STR0 increases.

[0102] Before the write process for all target sectors RSC (one rotation's worth of target sectors RSC) on the second track STR1 is completed, for example, when the write process has been performed on approximately 2 / 3 of the target sectors RSC on the second track STR1, damaged target sectors CSC1, CSC2, CSC3, CSC4, and CSC5 occur on the first track STR0, and the number of damaged target sectors CSC1 to CSC5 reaches the first threshold H1.

[0103] Therefore, if the write process to the second track STR1 is continued, there is a concern that a damaged sector CSC that makes it impossible to perform error correction may occur in the first track STR0. Therefore, the write process to the second track STR1 is not continued, and the remaining data that was to be written to the second track STR1 is written (recorded) by slipping to another area (such as a track other than the second track STR1).

[0104] As described above, when the magnetic disk device 1 is in a vibrating state, the frequency of executing slip processing to write remaining data to other areas increases before completing write processing for all target sectors RSC of the track TR. If slip processing is executed to write remaining data to a specific data area such as the media cache M of the disk DK, seek operations will occur frequently, resulting in a significant decrease in write performance.

[0105] Therefore, in the first embodiment, it is possible to provide a magnetic disk device 1 that can predict whether or not error correction for each track TR of a disk DK will reach its limit. For example, it is possible to suppress the occurrence of slip processing. Furthermore, in the first embodiment, it is possible to provide a magnetic disk device 1 that can improve the utilization efficiency of the track TR.

[0106] Next, the write processing method according to the first embodiment will be explained in detail. As shown in FIGS. 1 and 15, the write processing unit 62 can select a shingled recording format in which data of the second track STR1 is written over data of the first track STR0 in an overwrite direction d5 parallel to the radial direction d1 of the disk DK.

[0107] The error correction unit 64 can perform error correction on data of damaged target sectors CSC that are determined to have damaged data among the plurality of target sectors RSC on each of the first track STR0 and the second track STR1. Here, attention is focused on a write period in which a write process is performed on the plurality of target sectors RSC on the second track STR1 after a write process is performed on the plurality of target sectors RSC on the first track STR0.

[0108] During the write period, the correction limit prediction unit 65 can determine whether the data in each target sector RSC of the first track STR0 has been corrupted (whether the positioning error PE has exceeded the track margin TM).The correction limit prediction unit 65 can then generate prediction information that predicts whether error correction for the first track STR0 will reach its limit before the write process for all target sectors RSC of the second track STR1 is completed.

[0109] During the write period, the determination unit 66 can determine whether to allow the write processing unit 62 to continue the write process on the second track STR1 based on the prediction information. As a result, before the number of damage-target sectors CSC on the first track STR0 reaches a limit (for example, a first threshold H1), the determination unit 66 can determine whether to continue the write process on the second track STR1, to suspend the write process, or to execute slip processing.

[0110] Having the option to continue the write process makes it possible to suppress a decrease in the write performance of the magnetic disk device 1. Having the option to pause the write process makes it possible to wait for the disk DK to rotate without executing slip processing, thereby suppressing a significant decrease in write performance. Having the option to execute slip processing makes it possible to avoid a situation in which the number of damage-target sectors CSC in the first track STR0 exceeds a limit.

[0111] Here, in a direction parallel to the radial direction d1 of the disk DK, the first track STR0 is located in a first direction Da as viewed from the second track STR1. In the first direction Da, a position that is a track margin TM away from the position where the positioning error PE is 0 is defined as a reference radial position PTM. When the position of the write head WHD protrudes from the reference radial position PTM in the first direction Da during the write period, the correction limit prediction unit 65 can determine that the target sector RSC adjacent to the write head WHD in the radial direction d1 among the multiple target sectors RSC of the first track STR0 is a damaged target sector CSC.

[0112] The switching unit 67 can set the error correction mode to an effective mode that enables the error correction unit 64 to perform error correction on a track-by-track basis. If, during the write period, the prediction information is normal information that predicts that error correction on a track-by-track basis will not reach its limit, the switching unit 67 sets the error correction mode to the effective mode, and the determination unit 66 can cause the write processing unit 62 to continue the write process for the second track STR1. For example, if the magnetic disk device 1 is not in a vibration state, the determination unit 66 can determine to cause the write processing unit 62 to continue the write process.

[0113] The switching unit 67 can switch the error correction mode for each track between the valid mode or an invalid mode that invalidates the error correction mode. If, during the write period, the prediction information changes to abnormal information that predicts that error correction will reach its limit, the switching unit 67 switches the error correction mode to the invalid mode, and the determination unit 66 can cause the write processing unit 62 to suspend the write processing for the second track STR1.

[0114] When the error correction mode is switched to the invalid mode during the write period, the write processing unit 62 pauses the write processing for the second track STR1, drives the VCM 24 to maintain the position of the write head WHD in the radial direction d1 of the disk DK, waits for the disk DK to rotate, and then transitions to a write retry operation in which the write processing is resumed. For example, if the magnetic disk device 1 is vibrating, the write processing can be paused until the vibration subsides. Since slip processing involving a seek operation is no longer necessary, degradation of write performance can be suppressed.

[0115] If the prediction information changes to normal information after the write processing unit 62 transitions to a write retry operation, the switching unit 67 switches the error correction mode to the valid mode, and the determination unit 66 causes the write processing unit 62 to resume writing to the second track STR1. By returning the error correction mode to the valid mode by the switching unit 67, it is possible to resume writing to the remaining free sectors ESC, among the multiple target sectors RSC of the second track STR1, for which writing of data was postponed. This makes it possible to use the free sectors ESC as recording sectors USC in which valid data is written. The reduction in the number of free sectors ESC increases the utilization efficiency of the second track STR1.

[0116] The correction limit prediction unit 65 may determine early on whether the prediction information is normal or abnormal when it determines that the damage target sector CSC has first occurred in the first track STR0.

[0117] During the write period, the correction limit prediction unit 65 can manage the number of one or more damaged target sectors CSC that are determined to have damaged data among the multiple target sectors RSC in the first track STR0. Reaching the limit of error correction for the first track STR0 means that the number of one or more damaged target sectors CSC reaches a first threshold value H1. The first threshold value H1 is the upper limit of the number of one or more damaged target sectors CSC in the first track STR0 for which error correction can be performed by the error correction unit 64.

[0118] Here, the number of all target sectors RSC on the second track STR1 is set to G, the first threshold H1 is set to H1, and the number of target sectors RSC to which data is written during the above-mentioned write period from when data is first written on the second track STR1 until it is determined that a damaged target sector CSC has first occurred on the second track STR1 is set to n.

[0119] Formula 1 and Formula 2 are as follows: H1≧{(Gn) / n}+1 (Formula 1) H1<{(Gn) / n}+1 (Formula 2)

[0120] During the write period, when the correction limit prediction unit 65 determines that no damage target sector CSC has occurred in the first track STR0, the switching unit 67 can maintain the error correction mode in the valid mode.

[0121] On the other hand, when the correction limit prediction unit 65 determines for the first time during the write period that a damaged sector CSC has occurred in the first track STR0, the switching unit 67 processes the error correction mode as follows: That is, if the correction limit prediction unit 65 generates normal information that satisfies the above formula 1, the switching unit 67 can maintain the error correction mode as the valid mode. On the other hand, if the correction limit prediction unit 65 generates abnormal information that satisfies the above formula 2, the switching unit 67 can switch the error correction mode to the invalid mode.

[0122] As described above, the correction limit prediction unit 65 can quickly determine whether the predicted information is normal or abnormal. However, since one is a very small number (1<

[0123] When a plurality of damage-target sectors CSC occur in the first track STR0, the correction limit prediction unit 65 can determine whether the predicted information is normal information or abnormal information. The correction limit prediction unit 65 may start the above determination after two damage-target sectors CSC occur in the first track STR0, or may start the above determination after three damage-target sectors CSC occur in the first track STR0.

[0124] ​Here, let p be the number of target sectors RSC into which data was written during the write period from when it was determined that a damaged sector CSC had occurred last time on the first track STR0 until it was determined that the last damaged sector CSC had occurred on the first track STR0. Let q be the number of target sectors RSC into which data was written from when data was first written on the second track STR1 until it was determined that the last damaged sector CSC had occurred on the first track STR0. Let v be the number of damaged sectors CSC into which data was determined to be damaged until it was determined that the last damaged sector CSC had occurred on the first track STR0.

[0125] Formulas 3 and 4 are as follows: H1≧{(Gq) / p}+v (Equation 3) H1<{(Gq) / p}+v (Equation 4)

[0126] During the write period, when the correction limit prediction unit 65 determines that no damage target sector CSC has occurred in the first track STR0, the switching unit 67 can maintain the error correction mode in the valid mode.

[0127] On the other hand, if the correction limit prediction unit 65 determines for the second or subsequent time during the write period that a damaged sector CSC has occurred in the first track STR0, the switching unit 67 processes the error correction mode as follows: That is, if the correction limit prediction unit 65 generates normal information that satisfies the above formula 3, the switching unit 67 can maintain the error correction mode as the valid mode. On the other hand, if the correction limit prediction unit 65 generates abnormal information that satisfies the above formula 4, the switching unit 67 can switch the error correction mode to the invalid mode.

[0128] The slip processing unit 68 can perform slip processing. When the judgment unit 66 determines that error correction for the first track STR0 has reached its limit before writing data to all target sectors RSC of the second track STR1, the write processing unit 62 terminates the write processing for the second track STR1, and the multiple target sectors RSC of the second track STR1 are classified into multiple target sectors RSC (multiple recording sectors USC) for which the write processing has been performed and which belong to the first group, and one or more target sectors RSC (empty sectors ESC) for which the write processing has not been performed and which belong to the second group.

[0129] Furthermore, the slip processing unit 68 can perform slip processing to drive the VCM24 to position the write head WHD in the radial direction d1 of the disk DK so as to face the third data track TR of the disk DK, and write data for one or more target sectors RSC (empty sectors ESC) belonging to the second group to the third data track.

[0130] The slip processing unit 68 can also execute slip processing to write data to a memory external to the disk DK. When the judgment unit 66 determines that error correction for the first track STR0 has reached its limit before writing data to all target sectors RSC of the second track STR1, the write processing unit 62 terminates the write processing for the second track STR1, and the multiple target sectors RSC of the second track STR1 are classified into multiple target sectors RSC (multiple recording sectors USC) belonging to the first group and one or more target sectors RSC (empty sectors ESC) belonging to the second group.

[0131] Furthermore, the slip processing unit 68 can execute slip processing to write data for one or more target sectors RSC (empty sectors ESC) belonging to the second group to a memory (for example, the nonvolatile memory 90).

[0132] Next, a specific example of the above-mentioned write processing method will be described. FIG. 15 is a schematic diagram illustrating an example of the first track STR0 and the second track STR1 of the magnetic disk device 1, and is a diagram for explaining the write process for the first track STR0 and the second track STR1. The write process for the second track STR1 continues until the number of damage-target sectors CSC in the first track STR0 reaches three. When the number reaches three, the error correction prediction information changes to abnormality information, the write process for the second track STR1 is paused, the error correction mode is switched to invalid mode, and the disk DK switches to a rotation waiting operation. For ease of explanation, FIG. 15 also illustrates the first track STR0 and the like as if the circumferential direction were linear. FIG. 16 is a graph showing the change in the number of damage-target sectors CSC for the first track STR0 of FIG. 15, corresponding to the case where the prediction information is abnormality information. It also shows timing charts for the positioning error PE, the write gate WG, the error correction mode valid flag FTE, and the rotation waiting flag FWT during the write process for the second track STR1.

[0133] As shown in FIGS. 15 and 16, the write process for the first track STR0 is ideally performed without a positioning error PE (PE≈0, or PE=0). When starting the write process for the second track STR1, the gate detector 141 detects that the write gate WG is asserted (H level in this case). Note that the error correction mode valid flag FTE is initialized to 1, and the rotation wait flag FWT is initialized to 0. When the magnetic disk device 1 is in a vibrating state, a write operation to the second track STR1 may cause a damage target sector CSC to occur in the first track STR0. Note that there may be cases where two or more consecutive target sectors RSC in the circumferential direction (travel direction d2) are determined to be damage target sectors CSC.

[0134] When three damage-target sectors CSC occur in the first track STR0, the rate of increase in the damage-target sectors CSC predicts that the number of damage-target sectors CSC that may occur in the entire first track STR0 will exceed the first threshold H1 (5). In this case, when three damage-target sectors CSC occur in the first track STR0, the write process for the second track STR1 is paused and a write retry operation is initiated, and the track-by-track error correction mode is switched to the invalid mode. The gate detection unit 141 detects that the write gate WG has been negated (L level in this case). The error correction mode valid flag FTE is switched to 0, and the rotation wait flag FWT is switched to 1.

[0135] Here, we focus on the increase rate (1 / p) of the damage-target sectors CSC when the third damage-target sector CSC occurs in the first track STR0. If the write process to the second track STR1 is not paused, the final number H1p of damage-target sectors CSC predicted to occur in the first track STR0 is expressed by the following formula: H1p={(Gq) / p}+v

[0136] Since H1p>H1, if the write process is not paused, it is predicted that the error correction for the first track STR0 will reach its limit before the parity data is written to the final sector (parity sector) of the second track STR1, and the process will transition to slip processing.

[0137] The reason that the error correction limit for each track was reached earlier than expected is presumably because the head HD was in a swinging state due to external vibrations to the magnetic disk device 1. Therefore, before a situation requiring slip processing occurs, the write processing for the second track STR1 is paused and processing to wait for the disk DK to rotate is performed. This allows the magnetic disk device 1 to wait until the external vibrations to subside.

[0138] Fig. 17 is a diagram for explaining the write processing described above, following Fig. 15, and is a diagram for explaining the state in which, after the disk DK has undergone an operation of waiting for rotation and the predictive information regarding error correction for each track has changed to normal information, the process transitions to a write retry operation in which the write processing for the second track STR1 is resumed. For convenience of explanation, Fig. 17 also depicts the first track STR0, etc. as being linear in the circumferential direction.

[0139] Figure 18A is a graph showing the change in the number of damage-target sectors CSC for the first track STR0 of Figure 17, and corresponds to the case where the predicted increase rate of damage-target sectors CSC is 1 / p2 and the prediction information is abnormal information, and also shows a timing chart for the positioning error PE, write gate WG, error correction mode valid flag FTE, and rotation wait flag FWT during the period when write processing is being performed on the second track STR1.

[0140] Figure 18B is a graph following Figure 18A showing the change in the number of damage-target sectors CSC for the first track STR0, and corresponds to the case where the predicted increase rate of damage-target sectors CSC is 1 / p3 and the prediction information is abnormal information, and also shows a timing chart for the positioning error PE, write gate WG, error correction mode valid flag FTE, and rotation wait flag FWT during the period when write processing is being performed on the second track STR1.

[0141] Figure 18C is a graph following Figure 18B showing the change in the number of damage-target sectors CSC for the first track STR0, and corresponds to the case where the predicted increase rate of damage-target sectors CSC is 1 / p4 and the prediction information is abnormal information, and also shows a timing chart for the positioning error PE, write gate WG, error correction mode valid flag FTE, and rotation wait flag FWT during the period when write processing is being performed on the second track STR1.

[0142] 18D is a graph showing the change in the number of damage-target sectors CSC for the first track STR0, following FIG. 18C, in the case where the predicted increase rate of the damage-target sectors CSC is r / p5 and the prediction information is normal. It also shows a timing chart for the positioning error PE, write gate WG, error correction mode valid flag FTE, and rotation wait flag FWT during the write process to the second track STR1. In FIG. 18D, the positioning error PE for the first round is shown by a dashed line, and the positioning error PE for the second round is shown by a solid line. Furthermore, the write gate WG, error correction mode valid flag FTE, and rotation wait flag FWT for the second round are each shown by a solid line.

[0143] 17 and 18A, with the write process for the second track STR1 paused, the write head WHD is held at the position in the radial direction d1, and the correction limit prediction unit 65 calculates the predicted increase rate of the damaged target sector CSC while the disk DK is waiting for rotation. This is because the switching unit 67 determines whether it is possible to switch the track-by-track error correction mode from invalid mode to valid mode. Note that, once the rotation waiting process begins, the write processing unit 62 pauses the write process for the second track STR1 from the target sector RSCq onwards. When the write head WHD faces the target sector RSC(q+p2-1) of the second track STR1, PE>TM, which is the first time this has happened since the rotational delay process began. Since the predicted rate of increase in the damage target sector CSC is 1 / p2, which is greater than 2 / (Gq), H1p>H1, and the correction limit prediction unit 65 generates abnormality information. The switching unit 67 maintains the track-by-track error correction mode in the disabled mode and continues the rotational delay process. The write gate WG remains negated, the error correction mode valid flag FTE remains at 0, and the rotation wait flag FWT remains at 1.

[0144] As shown in Figures 17 and 18B, when the write head WHD faces the target sector RSC(q+p2+p3-1) of the second track STR1, PE>TM, which is the second time that PE>TM has occurred since the rotational delay process began. Since the predicted rate of increase in the damage target sector CSC is 1 / p3, which is greater than 2 / (Gq), H1p>H1, and the correction limit prediction unit 65 generates abnormality information. The switching unit 67 maintains the track-by-track error correction mode in the disabled mode and continues the rotational delay process. The write gate WG remains negated, the error correction mode valid flag FTE remains at 0, and the rotation wait flag FWT remains at 1.

[0145] As shown in Figures 17 and 18C, PE>TM occurs when the write head WHD faces the target sector RSC (q+p2+p3+p4-1) of the second track STR1, and this is the third time that PE>TM has occurred since the start of the rotational delay process. Since the predicted rate of increase in the damage target sector CSC is 1 / p4, which is greater than 2 / (Gq), H1p>H1 occurs, and the correction limit prediction unit 65 generates abnormality information. The switching unit 67 maintains the track-by-track error correction mode in the disabled mode and continues the rotational delay process. The write gate WG remains negated, the error correction mode valid flag FTE remains at 0, and the rotation wait flag FWT remains at 1.

[0146] As shown in Figures 17 and 18D, PE>TM is then established when the write head WHD faces the target sector RSC (q+p2+p3+p4+p5-1) of the second track STR1, and this is the fourth time that PE>TM has been established since the start of the rotation wait process. The number of p5s is equal to or exceeds {(Gq) / 2}. The expected rate of increase in the damage target sector CSC is r / p5. In the example of Figure 18D, the value of r is 1. If the value of r is 1 or less, in other words, if the number of times PE>TM occurs is once or less during the period when the write head WHD faces the p5 target sectors RSC, then H1p≦H1, and the correction limit prediction unit 65 can generate normal information.

[0147] As described above, the correction limit prediction unit 65 calculates the increase rate immediately after the track-based error correction mode is switched to the invalid mode, thereby making it possible to quickly determine whether the track-based error correction mode can be returned to the valid mode. On the other hand, if the correction limit prediction unit 65 determines that the vibration state of the magnetic disk device 1 has not subsided, it may postpone calculating the increase rate for a predetermined period (for example, the period until the write head WHD faces the target sector RSC0). For example, if PE>TM occurs two or more times during the write period for the second track STR1 and H1p>(α×H1), the correction limit prediction unit 65 can determine that the vibration state of the magnetic disk device 1 has not subsided. By postponing the calculation of the increase rate, the amount of calculation by the correction limit prediction unit 65 can be reduced. Note that α is, for example, 2. However, the value of α may be any value greater than 1.0 and is not limited to 2.

[0148] In the example of Fig. 18D, r = 1 and H1p = 4. Since the predicted increase rate r / p5 of the damage target sector CSC is less than or equal to 2 / (Gq), the correction limit prediction unit 65 generates normal information. The switching unit 67 can return the track-by-track error correction mode to the valid mode. Immediately after H1p≦H1, the error correction mode valid flag FTE is switched to 1. Thereafter, when the write head WHD faces the target sector RSCq of the second track STR1, the gate detection unit 141 detects that the write gate WG has been switched to asserted, and the rotation wait flag FWT is switched to 0. As described above, it is possible to resume the write process for the second track STR1 from the target sector RSCq.

[0149] As shown in Figures 17 and 18A to 18D, with the write process for the second track STR1 paused, the position of the write head WHD in the radial direction d1 is maintained, the disk DK undergoes one rotation wait process, and then the write process is resumed from the target sector RSCq where the write process was paused last time, in a write retry operation.

[0150] By providing a rotational wait period for the disk DK while writing data to the second track STR1, the vibration state of the magnetic disk device 1 subsides, the predicted rate of increase in the damage target sector CSC decreases, and H1p≦H1 is established. If H1p≦H1 is not established even after performing rotational wait processing for one rotation, rotational wait processing for two rotations, rotational wait processing for three rotations, etc. may be performed until H1p≦H1 is established.

[0151] Next, a write processing method according to the first embodiment will be described using a flowchart. Fig. 19 is a flowchart showing the write processing method according to the first embodiment. Fig. 20 is a flowchart for explaining in detail some of the steps in the flowchart shown in Fig. 19.

[0152] As shown in Figure 19, when starting the write process for the second track STR1, the rotation wait flag FWT is initialized to 0, the error correction mode valid flag FTE is initialized to 1, the number of written target sectors SN for the second track STR1 is initialized to 0, the number v of damaged target sectors is initialized to 0, and the rotation wait counter RN is initialized to 0.

[0153] FWT=0 FTE=1 SN=0 v=0 RN=0 First, in step STa1, during the write period, the write processing unit 62 starts write processing for a plurality of target sectors RSC of the second track STR1. Next, in step STa2, the correction limit prediction unit 65 predicts the error correction limit, and the process proceeds to step STa3. In step STa3, the judgment unit 66 judges whether the error correction for the first track STR0 has reached its limit.

[0154] If the error correction for the first track STR0 has not reached its limit (NO in step STa3), the process proceeds to step STa4, where the determination unit 66 determines whether there is a rotation wait state based on the rotation wait flag FWT. If there is no rotation wait state (YES in step STa4), the process proceeds to step STa5, where the write processing unit 62 executes a write process on the current target sector RSC of the second track STR1 (the target sector RSC that the write head WHD is currently facing), and then the process proceeds to step STa6. In step STa5, the slip processing unit 68 resets the rotation wait counter RN to 0 (RN=0). The rotation wait counter RN is recorded in the memory inside the slip processing unit 68 or in a memory inside the magnetic disk device 1, such as the nonvolatile memory 90. On the other hand, if there is a rotation wait state (NO in step STa4), the process proceeds to step STa6 without proceeding to step STa5.

[0155] Next, in step STa6, the current sector number SN of the second track STR1 is incremented, and then the process proceeds to step STa7, where the last target sector RSC of the second track STR1 is determined. If the last target sector RSC of the second track STR1 is not determined, the process proceeds to step STa2. On the other hand, if the last target sector RSC of the second track STR1 is determined, the write process for the current second track STR1 is terminated.

[0156] In step STa3, if it is determined that the error correction for the first track STR0 has reached its limit (YES in step STa3), the process proceeds to step STa8, where the slip processing unit 68 executes slip processing, registers the data for the remaining free sectors ESC in a replacement area (e.g., media cache M), and terminates the write processing for the second track STR1.

[0157] Next, step STa7 in FIG. 19 will be described in detail. 20, when the process proceeds to step STa7, first, in step STa11, it is determined whether the current sector number SN of the second track STR1 is the number (G-1) of the last target sector RSC. If the sector number SN is not the number (G-1) (NO in step STa11), the process proceeds to step STa2.

[0158] On the other hand, if the sector number SN is number (G-1) (YES in step STa11), proceed to step STa12. If there is no rotational wait state (YES in step STa12), the write process for the second track STR1 is terminated. If there is a rotational wait state (NO in step STa12), proceed to step STa13, reset (initialize) the sector number SN to 0, and proceed to step STa14.

[0159] When SN=0 and the target for detecting the positioning error PE returns to the first sector SC of the second track STR1, the slip processing unit 68 increments the rotation wait counter RN in step STa14. Then, the process proceeds to step STa15, where the slip processing unit 68 determines whether the rotation wait counter RN has reached the upper limit value RNL.

[0160] If the rotation wait counter RN has not reached the upper limit value RNL (NO in step STa15, RN < RNL), the process proceeds to step STa2. On the other hand, if the rotation wait counter RN has reached the upper limit value RNL (YES in step STa15, RN = RNL), the process proceeds to step STa8. Note that the upper limit value RNL is, for example, 3. However, the upper limit value RNL is not limited to 3 and may be any value among natural numbers.

[0161] Since this write processing method has a path that transfers from step STa15 to step STa8, it is possible to eliminate a state where the error correction mode for each track remains in the invalid mode for a long time. For the write processing of the second track STR1, it is not necessary to continuously wait for the rotation of the disk DK three times (RNL times) or more. Therefore, it is possible to avoid a situation where the transfer speed of the write data to the second track STR1 is significantly reduced.

[0162] Next, step STa2 in FIG. 19 will be described in detail. FIG. 21 is a diagram for explaining the write processing according to the first embodiment, and is a flowchart for explaining in detail another part of the steps of the flowchart shown in FIG. 19.

[0163] As shown in FIG. 21, when the process proceeds to step STa2, first, in step STb1, the correction limit prediction unit � calculates the increase rate of the number of damaged target sectors CSC. When the determination by the correction limit prediction unit � that a damaged target sector CSC has occurred in the first track STR0 is the first time, the increase rate is 1 / n, and when the determination by the correction limit prediction unit � that a damaged target sector CSC has occurred in the first track STR0 is the second time or later, the increase rate is 1 / p.

[0164] As described above, the above n is the number of target sectors RSC to which data is written during the write period from when data is first written to the second track STR1 until it is determined that the first damaged target sector CSC has occurred in the second track STR1, and the above p is the number of target sectors RSC to which data is written from when it is determined that the previous damaged target sector CSC has occurred in the first track STR0 until it is determined that the last damaged target sector CSC has occurred in the first track STR0. If it is determined that no damaged sectors CSC have occurred in the first track STR0, the increase rate is zero.

[0165] Subsequently, in step STb2, the correction limit prediction unit 65 calculates a predicted value (H1p) of the number of damaged target sectors CSC when it is assumed that data has been written to all target sectors RSC of the first track STR0. When the correction limit prediction unit 65 determines for the first time that a damaged target sector CSC has occurred in the first track STR0, the predicted value is {(Gn) / n}+1, and when the correction limit prediction unit 65 determines for the second or subsequent time that a damaged target sector CSC has occurred in the first track STR0, the predicted value is {(Gq) / p}+v. If it is determined that no damaged sector CSC has occurred in the first track STR0, the predicted value is zero (H1p=0).

[0166] Next, in step STb3, the judgment unit 66 judges whether the current valid flag FTE of the error correction mode is 1. If the error correction mode is the valid mode (YES in step STb3), the process proceeds to step STb4, where the correction limit prediction unit judges whether the predicted value (H1p) exceeds the first threshold value H1. If the predicted value (H1p) does not exceed the first threshold value H1 (H1p≦H1, NO in step STb4), the process proceeds to step STb9.

[0167] In step STb9, if neither the rotation waiting state nor the current target sector RSC of the second track STR1 is the target sector RSC to which data will be written next is applicable, or if only one of the above two cases is applicable (NO in step STb9), proceed to step STa3.

[0168] On the other hand, if the rotational wait state is in effect and the current target sector RSC of the second track STR1 is the target sector RSC to which data is to be written next (YES in step STb9), the process proceeds to step STb10, the rotational wait state is released (FWT=0), and the process proceeds to step STa3.

[0169] In step STb4, if the predicted value (H1p) exceeds the first threshold H1 (H1p>H1, YES in step STb4), the process proceeds to step STb6, where the switching unit 67 switches the error correction mode to the disabled mode (FTE=0), the process proceeds to step STb7, where the write processing unit 62 switches to the rotation waiting mode (FWT=1), and the process proceeds to step STa3.

[0170] In step STb3, if the error correction mode is the invalid mode (NO in step STb3), the process proceeds to step STb5, where the correction limit prediction unit determines whether the predicted value (H1p) exceeds the first threshold value H1. If the predicted value (H1p) exceeds the first threshold value H1 (H1p>H1, YES in step STb5), the current write process is maintained, and the process proceeds to step STa3.

[0171] On the other hand, if the predicted value (H1p) does not exceed the first threshold value H1 (H1p≦H1, NO in step STb5), the process proceeds to step STb8, where the switching unit 67 returns the error correction mode to the valid mode (FTE=1), and the process proceeds to step STa3. From the above, the timing for returning the error correction mode to the valid mode may be during the rotation waiting period, and the mode can be returned at any time.

[0172] Next, step STa3 in FIG. 19 will be described in detail. FIG. 22 is a diagram for explaining the write processing according to the first embodiment, and is a flowchart for explaining in detail another part of the steps in the flowchart shown in FIG.

[0173] 22, when proceeding to step STa3, first, in step STc1, the correction limit prediction unit 65 determines whether the positioning error PE exceeds the track margin TM. If the positioning error PE does not exceed the track margin TM (PE≦TM, NO in step STc1), the process proceeds to step STa4.

[0174] On the other hand, if the positioning error PE exceeds the track margin TM (PE>TM, YES in step STc1), the process proceeds to step STc2, where the correction limit prediction unit 65 increments the number v of damage-target sectors CSC that have occurred in the first track STR0. Then, in step STc3, the correction limit prediction unit 65 determines whether the number v of damage-target sectors CSC has reached a first threshold H1.

[0175] If the number v of sectors CSC to be damaged reaches the first threshold H1 (YES in step STc3), the process proceeds to step STa8. On the other hand, if the number v of sectors CSC to be damaged does not reach the first threshold H1 (v The above write processing method can be carried out in accordance with the flowcharts shown in FIGS.

[0176] ​According to the magnetic disk device 1 and write processing method of the first embodiment configured as described above, the magnetic disk device 1 includes a disk DK, a write head WHD, a write processing unit 62, an error correction unit 64, a correction limit prediction unit 65, and a judgment unit 66. The error correction unit 64 can perform error correction on data in damaged target sectors CSC that are determined to have corrupted data among the plurality of target sectors RSC on each of the first track STR0 and the second track STR1. Here, attention is focused on a write period in which, after a write process is performed on the plurality of target sectors RSC on the first track STR0, a write process is performed on the plurality of target sectors RSC on the second track STR1.

[0177] During the write period, the correction limit prediction unit 65 can determine whether the data in each target sector RSC of the first track STR0 has been corrupted (whether the positioning error PE has exceeded the track margin TM).The correction limit prediction unit 65 can then generate prediction information that predicts whether error correction for the first track STR0 will reach its limit before the write process for all target sectors RSC of the second track STR1 is completed.During the write period, the judgment unit 66 can determine whether to cause the write processing unit 62 to continue the write process for the second track STR1 based on the prediction information.

[0178] This allows the judgment unit 66 to determine whether to continue the write process on the second track STR1, to pause the write process, or to perform slip processing before the number of damage-target sectors CSC on the first track STR0 reaches the limit (first threshold H1).

[0179] Having the option to continue the write process makes it possible to suppress a decrease in the write performance of the magnetic disk device 1. Having the option to pause the write process makes it possible to wait for the disk DK to rotate, thereby suppressing a decrease in write performance due to slip processing. When the rotation wait state is released, the write process to the second track STR1 can be resumed, thereby improving the utilization efficiency of the second track STR1. Having the option to execute slip processing makes it possible to avoid a situation where the number of damage-target sectors CSC on the first track STR0 exceeds a limit.

[0180] From the above, it is possible to obtain a magnetic disk device 1 that can predict whether error correction for a track TR of a disk DK will reach its limit, and also to obtain a magnetic disk device 1 that can improve the utilization efficiency of the track TR.

[0181] (Second embodiment) Next, a second embodiment will be described. The magnetic disk device 1 has the same configuration as the magnetic disk device 1 of the first embodiment, except for the configuration described in this second embodiment. The write processing method is the same as the write processing method of the first embodiment, except for the procedure described in this second embodiment.

[0182] First, the write processing method according to the second embodiment will be described in detail. As shown in Figures 1 and 23, instead of determining whether the number H1p of final damaged sectors CSC predicted to occur in the first track STR0 exceeds the first threshold H1, the correction limit prediction unit 65 can determine whether the total excess amount H2p described below exceeds the second threshold H2.

[0183] The correction limit prediction unit 65 may determine early on whether the prediction information is normal or abnormal when it determines that the damage target sector CSC has first occurred in the first track STR0.

[0184] Here, attention is focused on a write period in which a write process is executed on a plurality of target sectors RSC of the second track STR1 after a write process is executed on a plurality of target sectors RSC of the first track STR0.

[0185] During the write period, the correction limit prediction unit 65 calculates the excess amount by which the position of the write head WHD protrudes from the reference radial position PTM in the first direction Da each time data is written to each target sector RSC of the second track STR1, and updates the total excess amount during the write period. Reaching the limit of error correction for the first track STR0 means that the total reaches a second threshold H2. The second threshold H2 is the upper limit of the total excess amount for which error correction can be performed by the error correction unit 64 on the first track STR0.

[0186] Here, the number of all target sectors RSC on the second track STR1 is G, the second threshold H2 is H2, the number of target sectors RSC to which data is written during the above-mentioned write period from when data is first written to the second track STR1 until it is determined that the position of the write head WHD has first protruded from the reference radial position PTM in the first direction Da is n, and the above-mentioned excess amount when it is determined that the position of the write head WHD has first protruded from the reference radial position PTM in the first direction Da is w.

[0187] Formulas 5 and 6 are as follows: H2≧{(w / n)·(Gn)}+w ···(Equation 5) H2<{(w / n)·(Gn)}+w ···(Equation 6)

[0188] When the correction limit prediction unit 65 determines that the position of the write head WHD does not protrude from the reference radial position PTM in the first direction Da during the write period, the switching unit 67 can maintain the error correction mode in the valid mode.

[0189] On one hand, when it is first determined during the writing period that the position of the write head WHD protrudes in the first direction Da from the reference radius position PTM, the switching unit 67 processes the error correction mode as follows. That is, when the correction limit prediction unit 65 generates normal information corresponding to the above formula 5, the switching unit 67 can maintain the error correction mode in the effective mode. On the other hand, when the correction limit prediction unit 65 generates abnormal information corresponding to the above formula 6, the switching unit 67 can switch the error correction mode to the invalid mode.

[0190] As described above, the correction limit prediction unit 65 can quickly determine whether the above prediction information is normal information or abnormal information. However, since the first excess amount w is very small compared to the second threshold H2 (w << H2), the determination regarding the above prediction information at the time when it is determined that the damaged target sector CSC first occurred in the first track STR0 may be postponed, and the writing process may be continued.

[0191] When a plurality of damaged target sectors CSC occur in the first track STR0, the correction limit prediction unit 65 can determine whether the above prediction information is normal information or abnormal information. The correction limit prediction unit 65 may start the above determination after two damaged target sectors CSC occur in the first track STR0, or may start the above determination after three damaged target sectors CSC occur in the first track STR0.

[0192] Here, during the above writing period, let the number of target sectors RSC in which data is written be p from the time when it is determined that the position of the write head WHD protruded in the first direction Da from the reference radius position PTM last time until the time when it is determined that the position of the write head WHD protrudes in the first direction Da from the reference radius position PTM this time. Let the number of target sectors RSC in which data is written be q from the time when data is first written to the second track STR1 until the time when it is determined that the position of the write head WHD protrudes in the first direction Da from the reference radius position PTM last time.

[0193] The excess amount w when it is determined that the position of the write head WHD has finally protruded from the reference radial position PTM in the first direction Da is defined as f. The total excess amount until it is determined that the position of the write head WHD has finally protruded from the reference radial position PTM in the first direction Da is defined as k.

[0194] Formulas 7 and 8 are as follows: H2≧{(f / p)·(Gq)}+k ···(Equation 7) H2<{(f / p)·(Gq)}+k ···(Equation 8)

[0195] When the correction limit prediction unit 65 determines that the position of the write head WHD does not protrude from the reference radial position PTM in the first direction Da during the write period, the switching unit 67 can maintain the error correction mode in the valid mode.

[0196] On the other hand, if it is determined that the position of the write head WHD has protruded from the reference radial position PTM in the first direction Da during the write period for the second or subsequent time, the switching unit 67 processes the error correction mode as follows: That is, if the correction limit prediction unit 65 generates normal information that satisfies the above formula 7, the switching unit 67 can maintain the error correction mode as the valid mode. On the other hand, if the correction limit prediction unit 65 generates abnormal information that satisfies the above formula 8, the switching unit 67 can switch the error correction mode to the invalid mode.

[0197] Next, a specific example of the write processing method according to the second embodiment will be described. Figure 23 is a schematic diagram showing an example of the first track STR0 and the second track STR1 of the magnetic disk device 1 according to the second embodiment, and is a diagram for explaining the write processing for the first track STR0 and the second track STR1, in which the write processing for the second track STR1 is continued until the total H2p of the excess amounts w for the write head WHD reaches or exceeds the second threshold H2, and the write processing for the second track STR1 is terminated when the total H2p reaches or exceeds the second threshold H2. For ease of explanation, the first track STR0 etc. are also depicted in Fig. 23 as being linear in the circumferential direction. Fig. 24 is a graph showing the change in total H2p for the first track STR0 in Fig. 23.

[0198] As shown in FIGS. 23 and 24, the write process for the first track STR0 is ideally executed without a positioning error PE (PE≈0, or PE=0). If the magnetic disk device 1 is in a vibrating state, when a write process is performed on the second track STR1, a sector CSC that may be damaged may occur in the first track STR0.

[0199] When one or more damaged sectors CSC occur in the first track STR0, the correction limit prediction unit 65 can predict whether the total H2p will exceed the second threshold H2 from the rate of increase of the excess amount w.

[0200] Next, a write processing method according to the second embodiment will be described using a flowchart. Fig. 25 is a diagram for explaining the write processing according to the second embodiment, and is a flowchart for explaining in detail another part of the steps in the flowchart shown in Fig. 19. Fig. 26 is a diagram for explaining the write processing according to the second embodiment, and is a flowchart for explaining in detail another part of the steps in the flowchart shown in Fig. 19.

[0201] First, step STa2 in FIG. 19 will be described in detail. 25, when proceeding to step STa2, first, in step STd1, the correction limit prediction unit 65 calculates the increase rate of the excess amount w. When the correction limit prediction unit 65 determines for the first time that a damage-target sector CSC has occurred in the first track STR0, the increase rate is w / n, and when the correction limit prediction unit 65 determines for the second or subsequent time that a damage-target sector CSC has occurred in the first track STR0, the increase rate is f / p. If it is determined that the position of the write head WHD does not protrude from the reference radial position PTM in the first direction Da, the increase rate is zero.

[0202] Next, in step STd2, the correction limit prediction unit 65 calculates a predicted value (H2p) of the total excess amount w when it is assumed that data has been written to all target sectors RSC of the first track STR0. When the correction limit prediction unit 65 determines for the first time that a damaged target sector CSC has occurred in the first track STR0, the predicted value is {(w / n)·(Gn)}+w, and when the correction limit prediction unit 65 determines for the second or subsequent time that a damaged target sector CSC has occurred in the first track STR0, the predicted value is {(f / p)·(Gq)}+k. If it is determined that the position of the write head WHD does not protrude from the reference radial position PTM in the first direction Da, the predicted value is zero (H2p=0).

[0203] Next, in step STd3, the judgment unit 66 judges whether the current valid flag FTE of the error correction mode is 1. If the error correction mode is the valid mode (YES in step STd3), the process proceeds to step STd4, where the correction limit prediction unit 65 judges whether the predicted value (H2p) exceeds the second threshold value H2. If the predicted value (H2p) does not exceed the second threshold value H2 (H2p≦H2, NO in step STd4), the process proceeds to step STd9.

[0204] In step STd9, if neither the rotation waiting state nor the current target sector RSC of the second track STR1 is the target sector RSC to which data will be written next is applicable, or if only one of the above two cases is applicable (NO in step STd9), proceed to step STa3.

[0205] On the other hand, if the rotational wait state is in effect and the current target sector RSC of the second track STR1 is the target sector RSC to which data is to be written next (YES in step STd9), the process proceeds to step STd10, the rotational wait state is released (FWT=0), and the process proceeds to step STa3.

[0206] In step STd4, if the predicted value (H2p) exceeds the second threshold H2 (H2p>H2, YES in step STd4), the process proceeds to step STd6, where the switching unit 67 switches the error correction mode to the disabled mode (FTE=0), the process proceeds to step STd7, where the write processing unit 62 switches to the rotation waiting mode (FWT=1), and the process proceeds to step STa3.

[0207] In step STd3, if the error correction mode is the invalid mode (NO in step STd3), the process proceeds to step STd5, where the correction limit prediction unit 65 determines whether the predicted value (H2p) exceeds the second threshold value H2. If the predicted value (H2p) exceeds the second threshold value H2 (H2p>H2, YES in step STd5), the current write process is maintained, and the process proceeds to step STa3.

[0208] On the other hand, if the predicted value (H2p) does not exceed the second threshold H2 (H2p≦H2, NO in step STd5), the process proceeds to step STd8, where the switching unit 67 returns the error correction mode to the valid mode (FTE=1), and the process proceeds to step STa3. From the above, the timing for returning the error correction mode to the valid mode may be during the rotation waiting period, and the mode can be returned at any time.

[0209] Next, step STa3 in FIG. 19 will be described in detail. 26, when proceeding to step STa3, first, in step STe1, the correction limit prediction unit 65 determines whether the positioning error PE exceeds the track margin TM. If the positioning error PE does not exceed the track margin TM (PE≦TM, NO in step STe1), the process proceeds to step STa4.

[0210] On one hand, if the positioning error PE exceeds the track margin TM (PE > TM, YES in step STe1), the process proceeds to step STe2, and the correction limit prediction unit 65 updates the total H2p of the excess amount w. Here, (PE - TM) in step STe2 is the excess amount w obtained when the determination in step STe1 is made. Then, in step STe3, the correction limit prediction unit 65 determines whether the total H2p of the excess amount w has reached the second threshold H2.

[0211] When the total H2p reaches the second threshold H2 (YES in step STe3), the process proceeds to step STa8. On the other hand, when the total H2p has not reached the second threshold H2 (H2p < H2, NO in step STe3), the process proceeds to step STa4. The writing process method according to the second embodiment can be implemented in accordance with the flowcharts shown in FIGS. 19, 20, 25, and 26.

[0212] In the magnetic disk device 1 and the writing process method according to the second embodiment configured as described above, the same effects as those in the first embodiment can be obtained. From the above description, a magnetic disk device 1 capable of predicting whether the error correction for the track TR of the disk DK reaches the limit can be obtained. Also, a magnetic disk device 1 capable of improving the utilization efficiency of the track TR can be obtained.

[0213] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and its equivalent scope. It is also possible to combine multiple embodiments as needed.

[0214] For example, the above-described technique is not limited to hybrid recording type magnetic disk devices, but may also be applied to shingled recording type magnetic disk devices and normal recording type magnetic disk devices. [Explanation of symbols]

[0215] 1...magnetic disk device, 60...MPU, 61...read / write processing unit, 62...write processing unit, 63...read processing unit, 64...error correction unit, 65...correction limit prediction unit, 66...determination unit, 67...switching unit, 68...slip processing unit, 70...volatile memory, 80...buffer memory, 90...nonvolatile memory, 100...host, 110...system controller, 120...driver IC, 130...head amplifier IC, 140...R / W channel, 150...HDC, 24...VCM, 30...arm, DK...disk, L...recording layer, U...user data area, M...media cache TR,STR,CTR...track, SC...sector, RSC...target sector, USC...recording sector, ESC...empty sector, VSC...unused sector, CSC...damaged target sector, HD...head, WHD...write head, RHD...read head, H1...first threshold, H2...second threshold, G,n,p,q,v...number, w,f...excess amount, k...total of excess amount w, PE...positioning error, TM...track margin, WOS...write-off track slice, PTM...reference radial position, d1...radial direction, d2...traveling direction, d3...rotational direction, d5...overwrite direction, Da...first direction.

Claims

1. a disk having a first data track and a second data track adjacent to each other on a recording layer, the first data track and the second data track each including a plurality of target sectors onto which data is to be written; a write head that writes data to the recording layer of the disc; a write processing unit capable of executing a write process for writing data to the recording layer; an error correction unit that performs error correction on data of a damaged target sector determined to have damaged data among the plurality of target sectors of each of the first data track and the second data track; a correction limit prediction unit; a determination unit, During a write period in which the write process is performed on the plurality of target sectors of the first data track and then the write process is performed on the plurality of target sectors of the second data track, The correction limit prediction unit It is possible to determine whether the data of the target sector of each of the first data tracks is corrupted; generating prediction information for predicting whether the error correction for the first data track will reach a limit before the write process for all target sectors of the second data track is completed; the determination unit determines whether to allow the write processing unit to continue the write process on the second data track based on the prediction information; Magnetic disk device.

2. a switching unit that can be set to an effective mode that enables the error correction unit to perform error correction on a track-by-track basis; If, during the write period, the prediction information is normal information that predicts that the error correction will not reach its limit, the switching unit sets the error correction mode to the valid mode, the determination unit causes the write processing unit to continue the write process on the second data track; 2. The magnetic disk drive according to claim 1.

3. the switching unit is capable of switching the error correction mode to the valid mode or an invalid mode that invalidates the error correction mode, If, during the write period, the prediction information is changed to abnormal information predicting that the error correction will reach its limit, the switching unit switches the error correction mode to the invalid mode, the determination unit causes the write processing unit to suspend the write processing on the second data track; 3. The magnetic disk drive according to claim 2.

4. an arm supporting the light head; an actuator for moving the arm, When the error correction mode is switched to the invalid mode during the write period, the write processing unit pauses the write process for the second data track, drives the actuator to maintain the position of the write head in the radial direction of the disk, waits for the disk to rotate, and then transitions to a write retry operation in which the write process is resumed.

4. The magnetic disk drive according to claim 3.

5. If the prediction information is changed to the normal information after the write processing unit has transitioned to the write retry operation, the switching unit switches the error correction mode to the valid mode, the determination unit causes the write processing unit to resume the write process on the second data track.

5. The magnetic disk drive according to claim 4.

6. During the write period, the correction limit prediction unit manages the number of one or more damaged target sectors determined to have damaged data among the plurality of target sectors of the first data track; The error correction for the first data track reaches a limit when the number of the one or more corrupted sectors reaches a first threshold; where: The number of all the target sectors in the second data track is G, H1 first thresholds, n is the number of target sectors to which data has been written during the write period from when data was first written to the second data track until it is determined that the damaged target sector has first occurred on the first data track; Formula 1 is changed to H1≧{(G−n) / n}+1, If Equation 2 is set to H1<{(G-n) / n}+1, then When the correction limit prediction unit determines that the damaged sector does not occur in the first data track during the write period, the switching unit maintains the error correction mode in the valid mode; or When the correction limit prediction unit determines for the first time during the write period that the damaged sector has occurred in the first data track, If the correction limit prediction unit generates the normal information corresponding to the formula 1, the switching unit maintains the error correction mode in the valid mode, or When the correction limit prediction unit generates the abnormality information corresponding to the formula 2, the switching unit switches the error correction mode to the invalid mode.

5. The magnetic disk drive according to claim 4.

7. During the write period, the correction limit prediction unit manages the number of one or more damaged target sectors determined to have damaged data among the plurality of target sectors of the first data track; The error correction for the first data track reaches a limit when the number of the one or more corrupted sectors reaches a first threshold; where: The number of all the target sectors in the second data track is G, H1 first thresholds, During the write period, the number of target sectors to which data has been written from the time when it was determined that the target sector had previously occurred on the first data track until the time when it was determined that the target sector had finally occurred on the first data track is p; The number of target sectors to which data has been written from the time when data was first written to the second data track until it is determined that the damaged target sector has finally occurred on the first data track is q; The number of the damage target sectors whose data has been determined to be damaged until it is determined that the damage target sector has last occurred in the first data track is v, Equation 3 is changed to H1≧{(G−q) / p}+v, If Equation 4 is set to H1<{(G−q) / p}+v, then When the correction limit prediction unit determines that the damaged sector does not occur in the first data track during the write period, the switching unit maintains the error correction mode in the valid mode; or When the correction limit prediction unit determines that the damaged sector has occurred in the first data track for the second or subsequent time during the write period, If the correction limit prediction unit generates the normal information corresponding to the formula 3, the switching unit maintains the error correction mode in the valid mode, or When the correction limit prediction unit generates the abnormality information corresponding to the formula 4, the switching unit switches the error correction mode to the invalid mode.

5. The magnetic disk drive according to claim 4.

8. During the write period, the correction limit prediction unit manages the number of one or more damaged target sectors determined to have damaged data among the plurality of target sectors of the first data track; The error correction for the first data track reaches its limit when the number of the one or more corrupted sectors reaches a first threshold.

2. The magnetic disk drive according to claim 1.

9. the first threshold is an upper limit value of the number of the one or more damage target sectors in the first data track for which the error correction can be performed by the error correction unit; 9. The magnetic disk drive according to claim 8.

10. the first data track is located in a first direction relative to the second data track in a direction parallel to the radial direction of the disk; during the write period, the correction limit prediction unit calculates an excess amount by which the position of the write head protrudes from a reference radial position in the first direction each time data is written to the target sector of each of the second data tracks, and updates the total of the excess amounts during the write period; the error correction for the first data track reaches a limit when the sum reaches a second threshold; where: The number of all the target sectors in the second data track is G, The second threshold is H2, n is the number of target sectors into which data has been written during the write period from when data was first written to the second data track until it is determined that the position of the write head has first protruded from the reference radial position in the first direction; The excess amount when it is determined that the position of the write head first protrudes from the reference radial position in the first direction is w, Formula 5 is changed to H2≧{(w / n)·(G−n)}+w, If Equation 6 is set to H2<{(w / n)·(G−n)}+w, then When the correction limit prediction unit determines that the position of the write head does not protrude from the reference radial position in the first direction during the write period, the switching unit maintains the error correction mode in the valid mode; or When it is determined for the first time during the write period that the position of the write head has protruded from the reference radial position in the first direction, If the correction limit prediction unit generates the normal information corresponding to the formula 5, the switching unit maintains the error correction mode in the valid mode, or When the correction limit prediction unit generates the abnormality information corresponding to the formula 6, the switching unit switches the error correction mode to the invalid mode.

5. The magnetic disk drive according to claim 4.

11. the first data track is located in a first direction relative to the second data track in a direction parallel to the radial direction of the disk; during the write period, the correction limit prediction unit calculates an excess amount by which the position of the write head protrudes from a reference radial position in the first direction each time data is written to the target sector of each of the second data tracks, and updates the total of the excess amounts during the write period; the error correction for the first data track reaches a limit when the sum reaches a second threshold; where: The number of all the target sectors in the second data track is G, The second threshold is H2, p is the number of target sectors into which data has been written during the write period from when it was determined that the position of the write head had previously protruded from the reference radial position in the first direction until when it was determined that the position of the write head had finally protruded from the reference radial position in the first direction; the number of target sectors in which data has been written from the time when data was first written to the second data track until it is determined that the position of the write head has finally protruded from the reference radial position in the first direction is q; f is the excess amount when it is determined that the position of the write head finally protrudes from the reference radial position in the first direction; The sum of the excess amounts until it is determined that the position of the write head finally protrudes from the reference radial position in the first direction is k, Formula 7 is changed to H2≧{(f / p)·(G−q)}+k, If Equation 8 is set to H2<{(f / p)·(G−q)}+k, then When the correction limit prediction unit determines that the position of the write head does not protrude from the reference radial position in the first direction during the write period, the switching unit maintains the error correction mode in the valid mode; or When it is determined that the position of the write head has protruded from the reference radial position in the first direction during the write period for the second or subsequent time, If the correction limit prediction unit generates the normal information corresponding to the formula 7, the switching unit maintains the error correction mode in the valid mode, or When the correction limit prediction unit generates the abnormality information corresponding to the formula 8, the switching unit switches the error correction mode to the invalid mode.

5. The magnetic disk drive according to claim 4.

12. the first data track is located in a first direction relative to the second data track in a direction parallel to the radial direction of the disk; during the write period, the correction limit prediction unit calculates an excess amount by which the position of the write head protrudes from a reference radial position in the first direction each time data is written to the target sector of each of the second data tracks, and updates the total of the excess amounts during the write period; The error correction for the first data track reaches its limit when the sum is equal to or greater than a second threshold.

2. The magnetic disk drive according to claim 1.

13. the second threshold is an upper limit of the total of the excess amounts of the first data tracks for which the error correction can be performed by the error correction unit; 13. The magnetic disk drive according to claim 12.

14. the first data track is located in a first direction relative to the second data track in a direction parallel to the radial direction of the disk; When the position of the write head protrudes from a reference radial position in the first direction during the write period, the correction limit prediction unit determines that a target sector adjacent to the write head in the first direction among the plurality of target sectors of the first data track is the damaged target sector.

2. The magnetic disk drive according to claim 1.

15. an arm supporting the light head; an actuator that moves the arm; A slip processing unit is further provided, When the determination unit determines that the error correction for the first data track has reached a limit before data is written to all target sectors of the second data track, the write processing unit completes the write process for the second data track, the plurality of target sectors of the second data track are classified into a plurality of target sectors for which the write process has been performed and which belong to a first group, and one or more target sectors for which the write process has not been performed and which belong to a second group; The slip processing section includes: driving the actuator to position the write head in the radial direction of the disk so that it faces a third data track of the disk; executing a slip process for writing data of the one or more target sectors belonging to the second group to the third data track; 2. The magnetic disk drive according to claim 1.

16. Memory and A slip processing unit is further provided, When the determination unit determines that the error correction for the first data track has reached a limit before data is written to all target sectors of the second data track, the write processing unit completes the write process for the second data track, the plurality of target sectors of the second data track are classified into a plurality of target sectors for which the write process has been performed and which belong to a first group, and one or more target sectors for which the write process has not been performed and which belong to a second group; The slip processing section includes: executing a slip process for writing data of the one or more target sectors belonging to the second group to the memory; 2. The magnetic disk drive according to claim 1.

17. the write processing unit is capable of selecting a shingled recording format in which data of the second data track is written overlapping data of the first data track in an overwrite direction parallel to the radial direction of the disk.

17. The magnetic disk drive according to claim 1.

Images