Magnetic disk drive

Abstract

To provide a magnetic disk device having high performance of write operation.SOLUTION: The controller executes the determination operation as the magnetic head passes through the servo sector during the write operation. In the determination operation, the controller calculates a first cumulative amount obtained by accumulating, in a first section, an evaluation amount corresponding to an amount by which the width of the adjacent track is narrowed by the write operation, and determines whether the first cumulative amount is smaller or larger than a threshold value corresponding to a correction limit of error correction in units of tracks. The first period includes a second period in which writing of data is completed and a third period in which data is written following the second period. The controller performs a write operation in response to determining that the first cumulative amount is larger than the threshold value by the determination operation, executes a rotational delay, and then re-executes the determination operation. The controller resumes the write operation in response to determining that the first cumulative amount is smaller than the threshold value by the re-executed determination operation.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] This embodiment relates to a magnetic disk device. [Background technology]

[0002] There are magnetic disk drives that have a function for protecting data written to each track on a track-by-track basis. With this function, the magnetic disk drive generates an error correction code for each track and can perform error correction on a track-by-track basis based on this error correction code. Error correction on a track-by-track basis is referred to as track error correction.

[0003] A magnetic disk drive with track error correction capability monitors the position of the magnetic head during a write operation, and if there is a risk that writing to a write target track will cause data on an adjacent track to become uncorrectable even with track error correction, the magnetic disk drive interrupts the write operation and performs a specified operation. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2023-119547 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one embodiment is to provide a magnetic disk drive with high performance in write operations. [Means for solving the problem]

[0006] According to one embodiment, a magnetic disk drive includes a magnetic disk, a magnetic head, and a controller. The magnetic disk includes a plurality of tracks. A plurality of servo sectors, on which servo information is recorded, are arranged at intervals in the circumferential direction on the plurality of tracks. The plurality of tracks includes a first track and a second track radially adjacent to the first track and written before the first track. Each of the first track and the second track includes a plurality of data sectors, and the plurality of data sectors includes a data sector in which an error correction code for error correction on a track-by-track basis is stored. The magnetic head writes and reads data to the magnetic disk. The controller reads the servo information when the magnetic head passes over each of the plurality of servo sectors, and performs a write operation on the first track while positioning the magnetic head over the first track based on the read servo information. During a write operation, the controller performs a determination operation when the magnetic head passes over the first servo sector, which is one of the plurality of servo sectors. In the determination operation, the controller calculates a first cumulative amount by accumulating an evaluation amount corresponding to the amount by which the width of the second track is narrowed by the write operation over a first section, and determines whether the first cumulative amount is smaller or larger than a first threshold value corresponding to the error correction limit. The first section includes a second section, which is a section where data writing in the circumferential direction of the first track is completed, and a third section, which is a section where data is written following the second section in the circumferential direction of the first track. The controller suspends the write operation when the determination operation determines that the first cumulative amount is larger than the first threshold value. After suspending the write operation, the controller waits for the magnetic disk to rotate, and re-executes the determination operation when the magnetic head passes the first servo sector again. The controller resumes the write operation when the re-executed determination operation determines that the first cumulative amount is smaller than the first threshold value. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device according to an embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of a magnetic disk according to the embodiment. [Figure 3] FIG. 3 is a schematic diagram for explaining the SMR method used in the magnetic disk device of the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a plurality of band areas provided on the magnetic disk of the embodiment. [Figure 5] FIG. 5 is a diagram for explaining track error correction according to the embodiment. [Figure 6] FIG. 6 is a diagram for explaining the PTS operation of the embodiment. [Figure 7] FIG. 7 is a diagram for explaining the track error estimation operation of the embodiment. [Figure 8] FIG. 8 is a diagram for explaining an example of the operation of the magnetic disk according to the embodiment after the write operation is interrupted in accordance with the result of the track error estimation operation. [Figure 9] FIG. 9 is a flowchart showing the operation of the magnetic disk device according to the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0008] A magnetic disk drive according to an embodiment will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to this embodiment.

[0009] (Embodiment) FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device 1 according to an embodiment.

[0010] The magnetic disk device 1 is connected to a host 2. The magnetic disk device 1 can receive access commands such as write commands and read commands from the host 2.

[0011] The magnetic disk device 1 includes a magnetic disk 11 having a recording surface formed on its surface. The magnetic disk device 1 writes and reads data to and from the magnetic disk 11 (more precisely, the recording surface of the magnetic disk 11) in response to an access command. Although the magnetic disk device 1 may include multiple magnetic disks 11, in this embodiment, for the sake of simplicity of explanation and illustration, the magnetic disk device 1 is shown to include one magnetic disk 11.

[0012] Data is written and read via a magnetic head 22. Specifically, the magnetic disk device 1 includes, in addition to a magnetic disk 11, a spindle motor 12, a motor driver IC (Integrated Circuit) 21, a magnetic head 22, an actuator arm 15, a voice coil motor (VCM) 16, a ramp 13, a head IC 24, a read / write channel (RWC) 25, RAM 27, a FROM (Flash Read Only Memory) 28, a buffer memory 29, a hard disk controller (HDC) 23, and a processor 26.

[0013] The magnetic disk 11 is rotated at a predetermined rotation speed by a spindle motor 12 attached to the rotation shaft of the magnetic disk 11. The spindle motor 12 is driven by a motor driver IC 21.

[0014] The motor driver IC 21 controls the rotation of the spindle motor 12 and the rotation of the VCM 16 .

[0015] The magnetic head 22 uses a write element 22w and a read element 22r provided therein to write and read data to and from the magnetic disk 11. The magnetic head 22 is attached to the tip of an actuator arm 15. The magnetic head 22 is moved in the radial direction of the magnetic disk 11 by a VCM 16 driven by a motor driver IC 21.

[0016] When the magnetic disk 11 is stopped from rotating, the magnetic head 22 is moved onto the ramp 13. The ramp 13 is configured to hold the magnetic head 22 at a position spaced apart from the magnetic disk 11.

[0017] During a read operation, the head IC 24 amplifies and outputs a signal read from the magnetic disk 11 by the magnetic head 22, and supplies the signal to the RWC 25. During a write operation, the head IC 24 amplifies a signal corresponding to the data to be written, which is supplied from the RWC 25, and supplies the signal to the magnetic head 22.

[0018] The HDC 23 controls the transmission and reception of data to and from the host 2 via the I / F bus, and controls the buffer memory 29, etc.

[0019] The buffer memory 29 is used as a buffer for data transmitted to and received from the host 2. For example, the buffer memory 29 is used to temporarily store data to be written to the magnetic disk 11 or data read from the magnetic disk 11.

[0020] The buffer memory 29 is configured, for example, by a volatile memory capable of high-speed operation. The type of memory that configures the buffer memory 29 is not limited to a specific type. The buffer memory 29 can be configured, for example, by a dynamic random access memory (DRAM), a static random access memory (SRAM), or a combination of these.

[0021] The RWC 25 performs modulation, including error correction coding, on the data to be written that is supplied from the HDC 23, and supplies the modulated data to the head IC 24. The RWC 25 also performs demodulation, including error correction, on the signal that is read from the magnetic disk 11 and supplied from the head IC 24, and outputs the digital data obtained by the demodulation to the HDC 23.

[0022] The processor 26 is, for example, a CPU (Central Processing Unit). A RAM 27, a FROM (Flash Read Only Memory) 28, and a buffer memory 29 are connected to the processor 26.

[0023] The FROM 28 is a non-volatile memory. Firmware (program data), various operating parameters, etc. are stored in the FROM 28. The firmware may be stored on the magnetic disk 11.

[0024] The RAM 27 is configured by, for example, DRAM, SRAM, or a combination of these. The RAM 27 is used as an operating memory by the processor 26. The RAM 27 is used as an area into which firmware is loaded and an area in which various management data is held.

[0025] The processor 26 performs overall control of the magnetic disk device 1 in accordance with firmware stored in the FROM 28 or the magnetic disk 11. For example, the processor 26 loads firmware from the FROM 28 or the magnetic disk 11 into the RAM 27, and controls the motor driver IC 21, head IC 24, RWC 25, HDC 23, etc. in accordance with the loaded firmware.

[0026] The configuration including the RWC 25, the processor 26, and the HDC 23 can also be considered as the controller 30. The controller 30 may be configured as a System-On-a-Chip (SoC). The controller 30 does not necessarily have to be configured as a SoC. In addition to these, the controller 30 may also include other elements (for example, a RAM 27, a ROM 28, a buffer memory 29, or the RWC 25).

[0027] FIG. 2 is a schematic diagram showing an example of the configuration of the magnetic disk 11 according to the embodiment.

[0028] During the manufacturing process, servo information is written to the magnetic disk 11 by, for example, a servo writer or by self-servo writing (SSW). Fig. 2 shows radially arranged servo areas 42 as an example of the arrangement of servo areas in which servo information is written. Data areas 43 in which data can be written are provided between the servo areas 42.

[0029] Based on servo information, a plurality of concentric tracks 41 are set in the radial direction of the magnetic disk 11. A plurality of data areas 43 are provided along the tracks 41, and a plurality of data sectors in which data is written are arranged.

[0030] The servo information includes servo marks, gray codes, burst patterns, and post codes. When writing data to or reading data from a data sector, the controller 30 generates a positional error signal (PES) based on the servo information read by the magnetic head 22 from the servo area 42. The PES indicates the amount of deviation from the track center of the target track. The controller 30 performs positioning of the magnetic head 22, i.e., seek control and tracking control, based on the PES obtained each time the magnetic head 22 passes over the servo area 42.

[0031] Hereinafter, a portion of a track 41 that is separated by a servo area 42 will be referred to as a servo sector. Because multiple servo areas 42 are arranged radially, each track 41 can be thought of as having multiple servo sectors arranged at intervals in the circumferential direction.

[0032] Hereinafter, data written in units of data sectors will be referred to as data pieces.

[0033] Known methods for writing data to a magnetic disk include a method called SMR (Shingled Magnetic Recording) and a method called CMR (Conventional Magnetic Recording).

[0034] 3 is a schematic diagram illustrating the SMR method used in the magnetic disk device 1 of the embodiment. In the SMR method, when data (referred to as first data) on a certain track 41 is written and then data (referred to as second data) on a track 41 radially adjacent to the track 41 is written, the tracks 41 are arranged so that the second data overlaps a portion of the first data. In other words, according to the SMR method, data on one of two tracks 41 radially adjacent to each other on the magnetic disk 11 is written so as to overlap a portion of data on the other of the two tracks 41.

[0035] For example, data on track #2 is written so that it overlaps part of the data already written on track #1. Similarly, data on track #3 is written so that it overlaps part of the data already written on track #2. In other words, according to the SMR method, data on one track repeatedly overlaps part of the data already written on an adjacent track.

[0036] This makes each track width TW narrower than the width (WHw) of the write element 22w, improving the recording density.

[0037] However, with the SMR system, because the track width TW is narrower than the width WHw of the write element 22w, updating a portion of the data for multiple tracks destroys the data on tracks adjacent to the updated data. To prevent this data destruction, the data for multiple tracks, including the portion of the data, is updated in a lump. The area of ​​multiple tracks that is updated in a lump is called a band.

[0038] Furthermore, according to the SMR method, writing to a plurality of tracks 41 within one band is permitted only from a predetermined end of the outer periphery or the inner periphery of the magnetic disk to the predetermined other end. In the example shown in FIG. 3, writing is performed for each track 41 from the outer periphery end toward the inner periphery end. The controller 30 may also be configured to perform writing for each track 41 from the inner periphery end toward the outer periphery end. The order of writing may also be set individually for each band.

[0039] In the following explanation, it is assumed that each track 41 included in the band area 130 is assigned a track number corresponding to the arrangement order in the radial direction, and in the SMR method, writing is performed for each track 41 in the order of the track numbers.

[0040] The CMR method is a method in which data on two tracks 41 adjacent to each other in the radial direction of the magnetic disk 11 is written so as not to overlap each other. With the CMR method, the width of each track 41 is the same as the width (WHw) of the write element 22w, so data at any position can be updated. Therefore, while the CMR method has a lower recording density than the SMR method, it also provides high random access performance.

[0041] The controller 30 of the embodiment is configured to write data received from the host 2 to the magnetic disk 11 using the SMR method. For this reason, the magnetic disk 11 is provided with a plurality of band areas.

[0042] FIG. 4 is a diagram showing an example of a plurality of band areas provided on the magnetic disk 11 according to the embodiment.

[0043] The recording surface 100 of the magnetic disk 11, i.e., the area where tracks 41 can be arranged, is divided radially into multiple storage areas 110. The multiple storage areas 110 include one media cache area 120 and multiple band areas 130. Areas called guard areas that cannot be specified as write destinations by the host 2 are provided between the storage areas 110. Note that the guard areas are not shown in FIG. 4.

[0044] The storage area 110 provided on the outermost radial side of the recording surface 100 is set as a media cache area 120. The media cache area 120 is a storage area used as a temporary storage location for data. Note that the location of the media cache area 120 is not limited to the outermost radial side. Two or more media cache areas 120 may be provided on the recording surface. Data can be written to the media cache area 120 using the CMR method.

[0045] One or more of the multiple storage areas 110 are set as band areas 130. Each band area 130 has multiple tracks 41. The maximum amount of user data that can be written to each band area 130, i.e., the storage capacity, is the same for all band areas 130. In each band area 130, data is written to all tracks 41 using the SMR method. When writing data to each band area 130, writing data beyond the guard area from the band area 130 that is the write destination to an adjacent band area 130 is prohibited.

[0046] Note that some of the multiple band areas 130 may be configured so that data is written using the CMR method.

[0047] During a write operation on one track 41, the magnetic head 22 may vibrate due to external factors. If the magnetic head 22 shifts toward a track 41 (referred to as the "adjacent track") adjacent to the track 41 being written to and written before the track 41 being written to, the width of the adjacent track is narrowed by the amount of shift of the magnetic head 22 toward the adjacent track. The amount of narrowing of the adjacent track due to the shift of the magnetic head 22 toward the adjacent track is referred to as the "narrowing amount." The narrowing amount is the amount of shift of the magnetic head 22 from the track center of the track 41 being written to toward the adjacent track. If the narrowing amount is greater than a predetermined amount, the magnetic field of the magnetic head 22 may interfere with the data written to the adjacent track, potentially resulting in the loss of that data. Furthermore, since the track width TW is narrower in the SMR system than in systems such as the CMR system, the vibration of the magnetic head 22 has a significant impact on the data on the adjacent track.

[0048] Therefore, the controller 30 of the embodiment has a track error correction function so that even if pieces of data written in some data sectors of adjacent tracks are lost due to vibration of the magnetic head 22, those pieces of data can be restored by error correction.

[0049] FIG. 5 is a diagram for explaining track error correction according to an embodiment. This diagram shows the configuration of one track 41. However, servo sectors are not shown. This diagram also shows write / read directions. The write / read directions are directions in which the magnetic head 22 moves relative to the track 41 as the magnetic disk 11 rotates. The magnetic head 22 writes or reads data to or from each track 41 in the write / read direction.

[0050] Each data sector on track 41 is identified by a sector number. A data sector with sector number x is represented as data sector #x. In the example shown in Fig. 5, track 41 has 11 data sectors, from data sector #0 to data sector #10.

[0051] A data fragment that is scheduled to be written to data sector #x and a data fragment that has been written to data sector #x are represented as data fragment #x.

[0052] The 11 data sectors are arranged in the order of sector numbers from a reference position in the circumferential direction in the write / read direction. In this specification, the beginning and end are defined based on the reference position and the write / read direction.

[0053] For example, the position that the magnetic head 22 passes first in the section from when it passes the reference position until it passes the reference position again is referred to as the track head. The position that the magnetic head 22 passes last in the section from when it passes the reference position until it passes the reference position again is referred to as the track end. Of data sectors #0 to #10, the data sector located at the start of the track, i.e., data sector #0, is referred to as the first data sector. Of data sectors #0 to #10, the data sector located at the end of the track, i.e., data sector #10, is referred to as the last data sector.

[0054] The last data sector #10 is a data sector for storing parity, which is an error correction code for correcting track errors. That is, writing in units of track 41 is performed, for example, as follows: First, data pieces are written to data sectors #0 to #9 in the order of sector numbers. Parity calculated based on the group of data pieces written to data sectors #0 to #9 is written to data sector #10 at the end of track 41.

[0055] The parity written to data sector #10 protects the group of data pieces written to data sectors #0 to #9 from errors. In other words, the parity written to sector #10 protects data on a track-by-track basis. The parity written to data sector #10 at the end of track 41 is referred to as track parity. Data sectors that store track parity, such as data sector #10, are sometimes referred to as parity sectors.

[0056] The method for calculating the track parity is not limited to a specific method. In one example, the track parity is generated by performing an XOR on a group of data pieces written to data sectors #0 to #9 for each bit position.

[0057] In this way, each track 41 is provided with a plurality of data sectors including a parity sector. The number of parity sectors provided in each track 41 is not limited to one. For example, two parity sectors may be provided in each track 41. In this case, for example, one of the two parity sectors stores parity generated from a group of data pieces written to data sectors located at even numbers from the start of the track. The other of the two parity sectors stores parity generated from a group of data pieces written to data sectors located at odd numbers from the start of the track. Three or more parity sectors may be provided in each track 41.

[0058] During a write operation, the controller 30 estimates whether a track error will occur if the write operation continues. A track error occurs when data on an adjacent track becomes uncorrectable even with track error correction. If it is estimated that a track error will occur if the write operation continues, the controller 30 interrupts the write operation and performs a predetermined operation. The predetermined operation includes a PTS (Partial Track Slip) operation.

[0059] 6 is a diagram for explaining the PTS operation of the embodiment. In this diagram, data fragments #0 to #9 and track parity are shown as one track's worth of data to be written to track #K, which is track 41 with track number K. This one track's worth of data is referred to as data for track #K. In a read operation for track #K, track #(K-1) corresponds to the track adjacent to track #K.

[0060] In a write operation to write data for track #K to track #K, if it is estimated at the timing when writing of data piece #6 is completed that a track error will occur, the controller 30 immediately stops the write operation and executes a PTS operation.

[0061] In the PTS operation, the controller 30 writes the track parity of the data for track #K to a system area (not shown). The system area is provided in a location different from the band area 130 where user data is written. The system area may be provided on the magnetic disk 11, or may be provided in a non-volatile memory such as FROM 28. In addition, the controller 30 writes data fragments #7 to #9 of the data for track #K that have not yet been written to track #K to track #(K+1). For example, the controller 30 writes data fragments #7 to #9 to data sectors #0 to #2 of track #(K+1).

[0062] As long as the data pieces for track #K that have not yet been written to track #K and the track parity are written to a location other than track #K, the write destination of this information is not limited to the locations exemplified above.

[0063] Whether or not a track error occurs is determined by the length of the circumferential section written when the amount of narrowing exceeds a predetermined threshold (referred to as the narrowing threshold) and the amount by which the amount of narrowing exceeds the narrowing threshold. Therefore, the controller 30 estimates whether or not a track error will occur by a determination operation based on the length of the circumferential section written when the amount of narrowing exceeds the narrowing threshold and the amount by which the amount of narrowing exceeds the narrowing threshold. This determination operation is referred to as a track error estimation operation.

[0064] The narrowing threshold is equal to or greater than 0 and equal to or less than the design value of the track width. The narrowing threshold is determined by the designer. For example, the upper limit of the narrowing amount at which data pieces written to adjacent tracks can be read normally without using track error correction is determined as the narrowing threshold. The method for determining the narrowing threshold is not limited to this. The narrowing threshold may also be a value obtained by subtracting a predetermined value from the upper limit.

[0065] FIG. 7 is a diagram for explaining the track error estimation operation of the embodiment.

[0066] The track error estimation operation is performed each time the magnetic head 22 passes a servo sector during a write operation. Fig. 7 illustrates the track error estimation operation when a write operation to track #M is performed and the magnetic head 22 reaches servo sector #N. Note that, by the time the write operation to track #M is performed, writing to the adjacent track, track #(M-1), has already been completed.

[0067] The controller 30 performs a write operation on track #M while positioning the magnetic head 22 over track #M. The controller 30 defines the amount by which the narrowing amount (i.e., the amount by which the track width of track #(M-1) is narrowed) exceeds the narrowing threshold as an evaluation amount, and calculates a first cumulative amount by accumulating the evaluation amount over a first section. The first section includes a second section and a third section. The second section is the section where writing in the circumferential direction of track #M is completed. The third section is the section where data is written following the second section. The controller 30 then estimates the occurrence of a track error based on a comparison between the first cumulative amount and a predetermined threshold (referred to as a first track error threshold) corresponding to the correction limit of track error correction. If the first cumulative amount is smaller than the first track error threshold, it can be estimated that a track error will not occur even if writing is continued. If the first cumulative amount is larger than the first track error threshold, it can be estimated that a track error will occur if writing is continued.

[0068] The third section is the section from the end of the second section to the next servo sector.

[0069] 7, the section from the beginning of track #M to servo sector #N of track #M corresponds to section 2. The section from servo sector #N of track #M to servo sector #(N+1) corresponds to section 3. The section from the beginning of track #M to servo sector #(N+1) of track #M corresponds to section 1.

[0070] Specifically, the calculation for accumulating the evaluation amount in the first section involves calculating the evaluation amount at each of a plurality of circumferential positions included in the first section and summing up the evaluation amounts at each of the plurality of circumferential positions included in the first section obtained by the calculation. Each of the plurality of circumferential positions is the circumferential position of a different data track included in track #(M-1), which is an adjacent track. In other words, the sum of the evaluation amounts at the plurality of circumferential positions in the first section where different adjacent data tracks are adjacent is set to the first cumulative amount.

[0071] As described above, the controller 30 can acquire a PES each time the magnetic head 22 passes a servo sector. However, there is not necessarily only one data sector between servo sectors. Therefore, the controller 30 calculates the radial position of the magnetic head 22 at the circumferential position of each data track of the adjacent tracks by interpolation based on the PES in each servo sector. Then, the controller 30 calculates the evaluation amount at the circumferential position of each data track of the adjacent tracks based on the radial position of the magnetic head 22 at the circumferential position of each data track of the adjacent tracks.

[0072] 7, writing has been completed for the second section, i.e., the section from the beginning of track #M to servo sector #N of track #M. For such a section where writing has been completed, the controller 30 calculates the evaluation amount at the circumferential position of each data track of the adjacent tracks based on the PES actually acquired for each servo sector by the magnetic head 22 during writing, etc.

[0073] In the third section, i.e., the section from servo sector #N to servo sector #(N+1) of track #M in the example shown in FIG. 7 , no writing has been performed yet. For such a section where writing has not yet been completed, the controller 30 predicts the evaluation amount at the circumferential position of each data track of the adjacent tracks based on one or more PESs obtained just before the magnetic head 22 passed through that section. For example, the controller 30 predicts the PES obtained when the magnetic head 22 passes servo sector #(N-1) and the PES obtained when the magnetic head 22 passes servo sector #N by extrapolating the PES obtained when the magnetic head 22 passes servo sector #(N+1) after servo sector #N. The controller 30 then calculates the evaluation amount at the circumferential position of each data track of the adjacent tracks in the third section using the PES obtained when the magnetic head 22 passes servo sector #(N+1).

[0074] The evaluation amount calculated by the controller 30 does not necessarily have to be the evaluation amount at the circumferential position of each data track of the adjacent tracks. The controller 30 may calculate the evaluation amount at the circumferential position of each data sector included in the write target track 41 (for example, track #M in FIG. 7), and may use the amount obtained by accumulating the obtained evaluation amounts as the first cumulative amount. Alternatively, the controller 30 may calculate the evaluation amount at each servo sector included in the write target track 41 (for example, track #M in FIG. 7), and may use the amount obtained by accumulating the obtained evaluation amounts as the first cumulative amount. Hereinafter, for ease of understanding, it is assumed that the controller 30 calculates the evaluation amount at each servo sector included in the write target track 41, and uses the amount obtained by accumulating the obtained evaluation amounts as the first cumulative amount.

[0075] The amount obtained by accumulating the evaluation amount in the second section is referred to as the second cumulative amount. The first cumulative amount is obtained by adding the amount obtained by accumulating the evaluation amount in the third section to the second cumulative amount.

[0076] PTS operations take a relatively long time. If PTS operations are performed many times while data is being written to one band area 130, the total time required to write to that one band area 130 increases, and the performance of the write operation deteriorates.

[0077] Furthermore, when a PTS operation is performed during a write operation on one track 41, unused data sectors are generated in that one track 41. However, the storage capacity of each band area 130 is predetermined. Therefore, if PTS operations are performed multiple times while data is being written to one band area 130, the number of data sectors in which data pieces can be written may be depleted in that one band area 130, making it impossible to write user data equivalent to the storage capacity. If it becomes impossible to write user data equivalent to the storage capacity, the controller 30 may re-execute the write operation in units of band areas 130.

[0078] Therefore, in the embodiment, if it is estimated by the track error estimation operation that a track error will occur, the controller 30 suspends the write operation and waits for the magnetic disk 11 to rotate once. Waiting for one rotation is referred to as rotation wait. When executing rotation wait while the write operation is suspended, the controller 30 executes the same positioning (i.e., tracking control) as when the write operation was being performed. Then, when the magnetic head 22 passes the point where the write operation was suspended, the controller 30 executes the track error estimation operation again.

[0079] The track error estimation operation is based solely on the predicted value of the PES, and the predicted value of the PES before the rotational delay is not necessarily equal to the predicted value of the PES after the rotational delay.

[0080] FIG. 8 is a diagram for explaining an example of the operation of the magnetic disk 11 according to the embodiment after the write operation is interrupted in accordance with the result of the track error estimation operation.

[0081] For example, suppose that during a write operation on track #M, magnetic head 22 vibrates due to an external factor, and the write operation is interrupted based on the result of the track error estimation operation when magnetic head 22 reaches servo sector #N, as shown in Figure 7. Thereafter, controller 30 continues the tracking operation of moving magnetic head 22 closer to the track center of track #M, while waiting for magnetic head 22 to rotate until it reaches servo sector #N. When magnetic head 22 reaches servo sector #N, controller 30 re-executes the track error estimation operation.

[0082] The controller 30 acquires the PES when the magnetic head 22 passes through servo sector #(N-1) and servo sector #N, even during the rotational wait. In the re-executed track error estimation operation, the controller 30 predicts the PES at servo sector #(N+1) based on the PES acquired at servo sector #(N-1) and servo sector #N during the rotational wait, and predicts the evaluation amount at servo sector #(N+1).

[0083] In the example shown in FIG. 8, the vibration of the magnetic head 22 gradually subsides during the rotation wait. As a result, the evaluation amount at servo sector #(N+1) becomes smaller than the evaluation amount at servo sector #(N+1) shown in FIG. 7, and the first cumulative amount becomes smaller than the first track error threshold. As a result, the re-executed track error estimation operation predicts that no track error will occur even if writing continues. Depending on the result, the controller 30 resumes the write operation immediately after the magnetic head 22 passes servo sector #N.

[0084] As described above, in the embodiment, although the magnetic disk 11 is required to rotate, the number of times the PTS operation is performed can be reduced. The time required for the magnetic disk 11 to rotate is significantly shorter than the time required for the PTS operation. Therefore, the degradation of the performance of the write operation caused by the execution of the PTS operation is suppressed. In other words, the performance of the write operation is improved. Furthermore, it is possible to prevent the execution of a write operation in units of band area 130, which would otherwise occur if the execution of the PTS operation made it impossible to write user data equivalent to the storage capacity.

[0085] 9 is a flowchart showing the operation of the magnetic disk device 1 according to the embodiment. This diagram shows the operation when the magnetic head 22 passes a certain servo sector (denoted as servo sector #i) during a write operation to a certain track 41. After starting the write operation, the controller 30 executes the series of operations shown in this diagram each time the magnetic head 22 passes a servo sector.

[0086] When the magnetic head 22 passes over the servo sector #i, the controller 30 acquires the PES at the servo sector #i based on the servo information read from the servo sector #i (S101).

[0087] The controller 30 determines whether the narrowing amount in the servo sector #i is greater than the narrowing threshold (S102). The controller 30 calculates the narrowing amount in the servo sector #i based on the PES in the servo sector #i, and executes the process of S102 using the narrowing amount in the servo sector #i.

[0088] If the narrowing amount in servo sector #i is greater than the narrowing threshold (S102: Yes), the controller 30 determines whether the number of servo sectors in the section from the beginning of the track to servo sector #i, in which the narrowing amount is greater than the narrowing threshold, is greater than a predetermined threshold (referred to as the second track error threshold) (S103).

[0089] As described above, whether or not a track error occurs is determined by the length of the circumferential section written when the narrowing amount exceeds the narrowing threshold and the amount by which the narrowing amount exceeds the narrowing threshold. In the process of S103, it is estimated whether or not a track error will occur if the write operation is continued based only on the length of the circumferential section written when the narrowing amount exceeds the narrowing threshold.

[0090] The second track error threshold is a threshold corresponding to the correction limit of track error correction, which is set for the length of a circumferential section written when the narrowing amount exceeds the narrowing threshold. If the length of a circumferential section written when the narrowing amount exceeds the narrowing threshold is greater than the second track error threshold, it is estimated that a track error will occur if the write operation is continued. If the length of a circumferential section written when the narrowing amount exceeds the narrowing threshold is smaller than the second track error threshold, it is estimated that a track error will not occur if the write operation is continued.

[0091] The length of the circumferential section written when the narrowing amount exceeds the narrowing threshold is expressed by the number of data sectors included in the adjacent track. The length of the circumferential section written when the narrowing amount exceeds the narrowing threshold may be expressed by the number included in the data track to be written, or by the number of servo sectors. Here, as an example, the length of the circumferential section written when the narrowing amount exceeds the narrowing threshold is expressed by the number of servo sectors.

[0092] If the number of servo sectors whose narrowing amount is greater than the narrowing threshold is greater than the second track error threshold (S103: Yes), the controller 30 immediately stops the write operation (S104). Then, the controller 30 executes the PTS operation (S105), and the operation ends. Therefore, the write operation to the area from servo sector #i to the end of the track is not performed.

[0093] If the number of servo sectors whose narrowing amount is greater than the narrowing threshold is not greater than the second track error threshold (S103: No), the controller 30 calculates the evaluation amount for the servo sector #i based on the PES for the servo sector #i (S106). The controller 30 calculates the evaluation value by subtracting the narrowing threshold from the narrowing amount for the servo sector #i. If the value obtained by subtracting the narrowing threshold from the narrowing amount is a negative value, the controller 30 sets the narrowing amount to 0.

[0094] Next, the controller 30 calculates the second accumulated amount, i.e., the amount obtained by accumulating the evaluation values ​​in the section from the beginning of the track to servo sector #i (S107). When the magnetic head 22 passes servo sector #(i-1), the controller 30 calculates the second accumulated amount for the section from the beginning of the track to servo sector #(i-1) by the process of S107. Therefore, the controller 30 acquires the second accumulated amount for the section from the beginning of the track to servo sector #i by adding the evaluation amount at servo sector #i obtained by the process of S106 to the second accumulated amount for the section from the beginning of the track to servo sector #(i-1). Note that the method of calculating the second accumulated amount is not limited to this.

[0095] The controller 30 determines whether the second cumulative amount is greater than a third track error threshold (S108). In S108, a determination operation similar to the track error estimation operation is performed based on the PES actually acquired during the write operation. The third track error threshold may be the same as or different from the first track error threshold.

[0096] If the second cumulative amount is greater than the third track error threshold (S108: Yes), the control proceeds to S104.

[0097] If the second cumulative amount is not greater than the third track error threshold (S108: No), the controller 30 predicts the PES at servo sector #(i+1) based on the latest PES at servo sector #(i-1) and the latest PES at servo sector #i (S109). The latest PES is the PES obtained most recently among the PES obtained during the write operation and the PES obtained during the rotational wait.

[0098] The controller 30 calculates the evaluation amount at the servo sector #(i+1) based on the predicted value of the PES at the servo sector #(i+1) (S110). The method of calculating the evaluation amount is the same as in S106.

[0099] The controller 30 acquires the first cumulative amount by adding the evaluation amount at the servo sector #(i+1) to the second cumulative amount (S111), and then determines whether the first cumulative amount is greater than the first track error threshold (S112).

[0100] The operations from S109 to S112 correspond to the track error estimation operation described above.

[0101] If the first cumulative amount is greater than the first track error threshold (S112: Yes), the controller 30 suspends the write operation (S113). Then, the controller 30 determines whether the number of rotational delays is greater than a predetermined threshold (referred to as a PTS threshold) (S114).

[0102] As mentioned above, the time required for rotational wait is significantly shorter than the time required for PTS operation. However, if rotational waits are performed multiple times in servo sector #i, the total time required for the multiple rotational waits may exceed the time required for PTS operation. To prevent the total time required for rotational waits from exceeding the time required for PTS operation, an upper limit is set on the number of rotational waits. The PTS threshold is a threshold that specifies the upper limit on the number of rotational waits. An integer greater than or equal to 1 is preset as the PTS threshold.

[0103] In S114, the count value of the number of rotational delays performed in response to the results of the track error estimation operation for servo sector #i is compared with the PTS threshold value. However, the number of times compared with the PTS threshold value is not limited to this. For example, the count value of the total number of rotational delays performed for one track 41 may be compared with the PTS threshold value.

[0104] If the number of times the rotation wait is executed is greater than the PTS threshold value (S114: Yes), the rotation wait is not executed and the control proceeds to S105.

[0105] If the number of rotational delays is not greater than the PTS threshold (S114: No), the controller 30 executes rotational delay (S115). Then, when the magnetic head 22 passes the servo sector #i again, control transitions to S109, and the track error estimation operation from S109 to S112 is executed again.

[0106] If the narrowing amount at servo sector #i is not greater than the narrowing threshold (S102: No), or if the first cumulative amount is not greater than the first track error threshold (S112: No), the controller 30 resumes or continues the write operation (S116), and the operation when the magnetic head 22 passed servo sector #i is completed.

[0107] In the above description, if the amount of narrowing in servo sector #i is equal to the narrowing threshold in the process of S102, control proceeds to S116. However, if the amount of narrowing in servo sector #i is equal to the narrowing threshold, control may proceed to S103 instead of S116.

[0108] In the above description, if the second cumulative amount is equal to the third track error threshold in the process of S108, the control proceeds to S109. If the second cumulative amount is equal to the third track error threshold, the control may proceed to S104 instead of S109.

[0109] In the above description, in the process of S112, if the first cumulative amount is equal to the first track error threshold, the control transitions to S116. If the first cumulative amount is equal to the first track error threshold, the control may transition to S113 instead of S116.

[0110] As described above, according to the embodiment, the controller 30 performs a track error estimation operation when the magnetic head 22 passes a servo sector (referred to as a first servo sector) during a write operation. The track error estimation operation is an operation for calculating a first cumulative amount by accumulating an evaluation amount corresponding to the amount by which the width of an adjacent track is narrowed by the write operation over a first section, and determining whether the first cumulative amount is smaller or larger than a first track error threshold corresponding to the correction limit of track error correction. The first section includes a second section (see, for example, the section from the beginning of the track to servo sector #N in FIG. 7 ) in which data has been written in the circumferential direction of the write target track 41, and a third section (see, for example, the section from servo sector #N to servo sector #(N+1) in FIG. 7 ) in which data is written following the second section in the circumferential direction of the write target track. The controller 30 interrupts the write operation when it is determined that the first cumulative amount is larger than the first track error threshold. After the write operation is interrupted, the controller 30 waits for the magnetic disk 11 to rotate and then re-executes the track error estimation operation when the magnetic head 22 passes the first servo sector again. When the re-executed track error estimation operation determines that the first cumulative amount is smaller than the first track error threshold, the controller 30 resumes the write operation.

[0111] Therefore, the number of times the PTS operation is performed can be reduced, instead of waiting for the rotation of the magnetic disk 11. This improves the performance of the write operation.

[0112] Furthermore, according to the embodiment, the controller 30 calculates a second cumulative amount by accumulating the evaluation amounts in the second section based on the PESs acquired from each servo sector included in the second section during the execution of a write operation. The controller 30 also predicts the evaluation amount in the third section based on the PES in the first servo sector and the PES in the servo sector (referred to as the second servo sector) that the magnetic head 22 passes through immediately before the first servo sector. The controller 30 then acquires the first cumulative amount by adding the evaluation amount in the third section to the second cumulative amount.

[0113] In this way, the controller 30 obtains the evaluation amount in the third section through prediction.

[0114] Also, according to the embodiment, the controller 30 acquires the PES at the first servo sector and the PES at the second servo sector during the rotational wait after the interruption of the write operation, and predicts the evaluation quantity in the third section using the PES at the first servo sector and the PES at the second servo sector acquired during the rotational wait after the interruption of the write operation.

[0115] Therefore, if the vibration of the magnetic head 22 subsides during the rotational wait, the track error estimation operation that is re-executed when the rotational wait ends may result in an estimate that no track error will occur even if writing continues. In other words, it becomes possible to resume the write operation after the rotational wait.

[0116] According to the embodiment, the controller 30 uses the evaluation amount in the servo sector that the magnetic head 22 passes through immediately after the first servo sector as the evaluation amount in the third section.

[0117] Furthermore, according to the embodiment, the evaluation amount is an amount obtained by subtracting the narrowing threshold from the amount of deviation of the magnetic head 22 from the track center of the track 41 to be written toward the adjacent track.

[0118] As described above, the narrowing threshold is equal to or greater than 0 and equal to or less than the designed value of the track width, and is determined by the designer.

[0119] Furthermore, according to the embodiment, if the re-executed track error estimation operation determines that the first accumulated amount is greater than that in the first track error estimation operation and the number of rotational waits is not greater than the PTS threshold, the controller 30 further executes rotational wait and re-executes the track error estimation operation as the magnetic head 22 passes the first servo sector. If the re-executed track error estimation operation determines that the first accumulated amount is greater than the first track error threshold and the number of rotational waits is greater than the PTS threshold, the controller 30 executes the PTS operation.

[0120] Therefore, it is possible to prevent the total time required for the rotational waits from exceeding the time required for the PTS operation due to the rotational waits being executed multiple times.

[0121] Although several 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 embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0122] 1 magnetic disk device, 2 host, 11 magnetic disk, 12 spindle motor, 13 ramp, 15 actuator arm, 16 VCM, 21 motor driver IC, 22 magnetic head, 22r read element, 22w write element, 23 HDC, 24 head IC, 25 RWC, 26 processor, 27 RAM, 28 FROM, 29 buffer memory, 30 controller, 41 track, 42 ​​servo area, 43 data area, 100 recording surface, 110 storage area, 120 media cache area, 130 band area.

Claims

1. a magnetic disk comprising a plurality of tracks, on which a plurality of servo sectors, on which servo information is recorded, are arranged at intervals in a circumferential direction, the plurality of tracks comprising a first track and a second track, the second track being adjacent to the first track in a radial direction and written before the first track, the first track and the second track each comprising a plurality of data sectors, the plurality of data sectors including a data sector in which an error correction code for error correction in a track unit is stored; a magnetic head for writing data to and reading data from the magnetic disk; reading servo information when the magnetic head passes through each of the plurality of servo sectors, and performing a write operation on the first track while positioning the magnetic head over the first track based on the servo information that has been read; a determining operation is performed when the magnetic head passes a first servo sector that is one of the plurality of servo sectors during the write operation, the determining operation is an operation of calculating a first cumulative amount by accumulating an evaluation amount corresponding to an amount by which the width of the second track is narrowed by the write operation in a first section, and determining whether the first cumulative amount is smaller or larger than a first threshold value corresponding to a correction limit of the error correction, the first section including a second section in which writing of data in the circumferential direction of the first track is completed, and a third section in which data is written following the second section in the circumferential direction of the first track; interrupting the write operation in response to the determination that the first cumulative amount is greater than the first threshold value; After the write operation is interrupted, the magnetic disk is rotated and the determination operation is re-executed when the magnetic head passes over the first servo sector again; restarting the write operation in response to the determination that the first cumulative amount is smaller than the first threshold value in the re-executed determination operation; A controller; A magnetic disk device comprising:

2. the controller calculates a second cumulative amount by accumulating the evaluation amount in the second section based on servo information read from each servo sector included in the second section among the plurality of servo sectors during execution of the write operation, predicts the evaluation amount in the third section based on the servo information read from the first servo sector and the servo information read from the second servo sector, and obtains the first cumulative amount by adding the predicted evaluation amount in the third section to the second cumulative amount; the second servo sector is a servo sector that the magnetic head passes just before the first servo sector; 2. The magnetic disk drive according to claim 1.

3. The controller reading servo information from the first servo sector and reading servo information from the second servo sector while waiting for the magnetic disk to rotate; In the re-executed determination operation, the evaluation amount in the third section is predicted using servo information read from the first servo sector during the execution of rotational wait of the magnetic disk and servo information read from the second servo sector during the execution of rotational wait of the magnetic disk.

3. The magnetic disk drive according to claim 2.

4. the evaluation amount in the third section is the evaluation amount in a servo sector that the magnetic head passes through immediately after the first servo sector; 4. The magnetic disk drive according to claim 3.

5. the evaluation amount is an amount obtained by subtracting a second threshold value from the amount of deviation of the magnetic head from the track center of the first track toward the second track; 2. The magnetic disk drive according to claim 1.

6. The controller If the re-executed determination operation determines that the first cumulative amount is greater than the first threshold value and the number of times that rotational delay of the magnetic disk has been executed is not greater than a second threshold value, the magnetic disk is further rotated and the determination operation is re-executed as the magnetic head passes over the first servo sector; If the re-executed determination operation determines that the first cumulative amount is greater than the first threshold value and the number of times that the magnetic disk has been waiting for rotation is greater than the second threshold value, at least data that has not yet been written to the first track is written to a position different from the first track.

6. The magnetic disk drive according to claim 1.

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