Magnetic disc device

Abstract

To provide a magnetic disc device capable of favorably setting WOS.SOLUTION: A controller of a magnetic disc device acquires a RRO correction value for performing RRO correction at a position of a target data track through interpolation using a plurality of RRO correction values obtained by RRO measurement at each of a plurality of first positions in write operation. A controller sets WOS based on a permitted write range change determination distance as a distance between the first position included in the plurality of first positions and closest to the target data track and the target data track in the write operation.SELECTED DRAWING: Figure 9

Description

Technical Field

[0001] This embodiment relates to a magnetic disk drive.

Background Art

[0002] During a write operation in a magnetic disk drive, a write permission range centered on the track center is set in the radial direction. Then, the magnetic disk drive executes a write when the position of the magnetic head is within the write permission range. The magnetic disk drive refrains from writing when the position of the magnetic head deviates from the write permission range. The magnetic disk drive determines whether the position of the magnetic head is within the write permission range or has deviated from the write permission range based on a comparison between the positioning error with respect to the data track of the write target and a threshold value corresponding to the boundary of the write permission range. The threshold value is referred to as WOS (Write Offtrack Slice) or DOL (Drift Off Level). Hereinafter, the threshold value is denoted as WOS.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] One embodiment aims to provide a magnetic disk drive capable of suitably setting WOS.

Means for Solving the Problems

[0005] According to one embodiment, a magnetic head, a magnetic disk, and a controller are provided. The magnetic disk includes a plurality of data tracks. The controller performs a write operation on one of the plurality of data tracks using the magnetic head. In the write operation, the controller obtains a second RRO correction value, which is an RRO correction value at a second position, by interpolation using a plurality of first RRO correction values obtained by measuring RRO (Repeatable RunOut) at each of a plurality of first positions. Then, when positioning the magnetic head on the first data track, the controller performs RRO correction using the second RRO correction value. The plurality of first positions are a plurality of radial positions in the radial direction of the magnetic disk, and the second position is the position of the first data track, which is one of the data tracks. Further, in the write operation, the controller sets a threshold value based on a write permission range change determination distance, which is the distance between the second position and the first position among the plurality of first positions that is closest to the second position. When the positioning error is smaller than the threshold value, the controller performs writing to the first data track. When the positioning error is larger than the threshold value, the controller refrains from writing to the first data track.

Brief Description of the Drawings

[0006]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0007] The magnetic disk device according to the embodiment will be described in detail below with reference to the accompanying drawings. Note that the present invention is not limited to this embodiment.

[0008] (Embodiment) FIG. 1 is a schematic diagram showing an example of the configuration of the magnetic disk device 1 of the embodiment.

[0009] The magnetic disk device 1 is connected to the host 2. The magnetic disk device 1 can receive an access command from the host 2. The access command includes a write command and a read command.

[0010] The magnetic disk device 1 includes a magnetic disk 11 having a magnetic layer formed on its surface. The magnetic disk device 1 performs access to the magnetic disk 11 in response to an access command. The access includes writing data and reading data.

[0011] Writing and reading of data are performed by the magnetic head 22. Specifically, in addition to the magnetic disk 11, the magnetic disk device 1 includes a spindle motor (SPM) 12, a ramp 13, an actuator arm 15, a voice coil motor (VCM) 16, a servo controller (SVC) 21, a magnetic head 22, a hard disk controller (HDC) 23, a preamplifier 24, a read / write channel (RWC) 25, a processor 26, a FROM (Flash Read Only Memory) 28, and a DRAM (Dynamic Random Access Memory) 29.

[0012] The magnetic disk 11 is rotated at a predetermined rotational speed by the coaxially attached SPM 12.

[0013] The SVC 21 is an integrated circuit having a function as a driver for driving the SPM 12 and the VCM 16. The processor 26 controls the rotation of the SPM 12 and the rotation of the VCM 16 via the SVC 21.

[0014] The magnetic head 22 writes to and reads from the magnetic disk 11 by the write head 22w and the read head 22r provided thereon. Further, the magnetic head 22 is attached to the tip of the actuator arm 15. The magnetic head 22 is moved in the radial direction of the magnetic disk 11 by the VCM 16 driven by the SVC 21. Note that either one or both of the write head 22w and the read head 22r provided on the magnetic head 22 may be provided in plural for each single magnetic head 22.

[0015] When the rotation of the magnetic disk 11 stops, etc., the magnetic head 22 is moved onto the ramp 13. The ramp 13 is configured to hold the magnetic head 22 at a position separated from the magnetic disk 11.

[0016] The preamplifier 24 is an integrated circuit that writes and reads data via the magnetic head 22. During the read operation, the preamplifier 24 amplifies the signal read by the magnetic head 22 from the magnetic disk 11 and outputs it, supplying it to the RWC 25. Also, during the write operation, the preamplifier 24 amplifies the signal corresponding to the data to be written supplied from the RWC 25 and supplies it to the magnetic head 22.

[0017] The HDC 23 controls the transmission and reception of data with the host 2 via the I / F bus and controls the DRAM 29, etc.

[0018] The DRAM 29 is used as a buffer for data transmitted and received with the host 2. For example, the DRAM 29 is used to temporarily store the data to be written or the data read from the magnetic disk 11.

[0019] Also, the DRAM 29 is used as an operating memory by the processor 26. The DRAM 29 is used as an area where the firmware program is loaded and an area where various management data is temporarily stored.

[0020] The RWC 25 modulates the data to be written supplied from the HDC 23 and supplies it to the preamplifier 24. Also, the RWC 25 performs demodulation including error correction on the signal read from the magnetic disk 11 and supplied from the preamplifier 24, and then outputs the signal to the HDC 23 as digital data.

[0021] The processor 26 is, for example, a CPU (Central Processing Unit). The FROM (Flash Read Only Memory) 28 and the DRAM 29 are connected to the processor 26.

[0022] The FROM 28 stores the firmware program and various setting information, etc. Note that the firmware program may be stored in the magnetic disk 11.

[0023] The processor 26 performs overall control of this magnetic disk device 1 according to the firmware program stored in the FROM 28 or the magnetic disk 11. For example, the processor 26 loads the firmware program from the FROM 28 or the magnetic disk 11 into the DRAM 29, and executes control of the SVC 21, the preamplifier 24, the RWC 25, the HDC 23, etc. according to the firmware program loaded into the DRAM 29.

[0024] Note that part or all of the functions of the processor 26 may be realized by a hardware circuit such as an FPGA (Field-Programmable Gate Array) or an ASIC (Application Specific Integrated Circuit).

[0025] The HDC 23, the RWC 25, and the processor 26 are configured as an SoC (System-On-a-Chip) 30 which is an integrated circuit. The SoC 30 may include other elements (for example, the FROM 28, or the DRAM 29, etc.) in addition to these. Note that the SoC 30 is an example of a controller.

[0026] Note that in FIG. 1, one magnetic disk 11 is shown. However, the magnetic disk device 1 may include a plurality of magnetic disks 11. When the magnetic disk device 1 includes a plurality of magnetic disks 11, the plurality of magnetic disks 11 are integrally rotated by the SPM 12.

[0027] Also, when the number of magnetic disks 11 included in the magnetic disk device 1 is N, the number of recordable surfaces where data can be written is 2N (N is an integer of 1 or more). The magnetic disk device 1 includes 2N magnetic heads 22 for accessing different recordable surfaces in order to access the 2N recordable surfaces. The 2N magnetic heads 22 shall be identified by the magnetic head number.

[0028] FIG. 2 is a schematic diagram showing an example of the configuration of the magnetic disk 11 of the embodiment.

[0029] In this figure, the radial direction, circumferential direction, inner diameter (Inner Diameter: ID) direction, and outer diameter (Outer Diameter: OD) direction are shown. In the radial direction, the direction from the edge of the magnetic disk 11 toward the center is the inner diameter (Inner Diameter: ID) direction, and the direction from the center of the magnetic disk 11 toward the edge is the outer diameter (Outer Diameter: OD) direction.

[0030] In the manufacturing process of the magnetic disk 11, servo data used for positioning the magnetic head 22 is written, for example, by a servo writer or by self-servo write (SSW). According to FIG. 2, as an example of the arrangement of servo regions where servo data is written, a plurality of servo regions SV are formed radially in the radial direction and at predetermined intervals in the circumferential direction. A data area DA where data is written is arranged between two servo regions SV that are continuous in the circumferential direction.

[0031] A plurality of concentric servo tracks 41 are provided in the radial direction of the magnetic disk 11. Also, a plurality of data tracks (denoted as data track DTRK) are set on the surface where the plurality of servo tracks 41 are provided.

[0032] There are variations in the recording performance for each magnetic head 22 due to manufacturing variations. Also, there are variations in the data holding ability on the recording surface of the magnetic disk 11. Thus, in one example, the recording surface is divided into a plurality of zones in the radial direction, and the arrangement density of the data tracks DTRK and the recording density of the data along the data tracks DTRK are determined for each combination of zone and magnetic head 22. That is, the track pitch of the data tracks DTRK can be different for each zone and for each recording surface. Note that the arrangement density of the data tracks DTRK is referred to as TPI (Track Per Inch). The recording density of the data along the data tracks DTRK is referred to as BPI (Bit Per Inch).

[0033] Note that as the arrangement method of the data track DTRK, there are a method called CMR (Conventional Magnetic Recording) and a method called SMR (Shingled Magnetic Recording). The CMR method is a method in which each data track DTRK is arranged so as not to overlap with the data track DTRK adjacent in the radial direction. The SMR method is a method in which the data of one of the two data tracks DTRK adjacent to each other in the radial direction of the magnetic disk 11 is written overlapping a part of the data of the other data track DTRK among the two data tracks DTRK. According to the SMR method, since the track pitch of the data track DTRK is made narrower than the width (WHw) of the write head 22w of the magnetic head 22, a higher recording density can be obtained compared to the CMR method. However, according to the SMR method, the random write performance is lower than that of the CMR method.

[0034] The arrangement method of the data track DTRK may be fixed to the CMR method or the SMR method, or may be dynamically changeable between the CMR method and the SMR method. For example, the magnetic disk device 1 may be configured to be able to change the arrangement method of the data track DTRK between the CMR method and the SMR method for a part of the area or the entire area of the recording surface based on an instruction from the user. Note that a hard disk device capable of changing the arrangement method of the data track DTRK between the CMR method and the SMR method is called a hybrid HDD (Hard Disk Drive).

[0035] The magnetic disk device 1 stores the setting of the positional relationship between the plurality of servo tracks 41 and each data track DTRK. The magnetic disk device 1 executes control (referred to as positioning control) for positioning the magnetic head 22 at the target data track DTRK based on the servo data recorded in the servo area SV. The positioning control includes a seek operation which is an operation of moving the magnetic head 22 in the radial direction toward the target data track DTRK, a tracking operation of maintaining the magnetic head 22 on the target data track DTRK, and the like.

[0036] Servo data may include a preamble, servo marks, Gray code, a burst pattern, and a post code.

[0037] The preamble is a single-period pattern data that periodically changes in the circumferential direction. The preamble is used to adjust the amplitude, phase, and frequency of sampling data when the servo waveform read by the read head 22r is captured as sampling data in the RWC 25 based on the servo clock.

[0038] The servo marks are pattern data for determining the demodulation timing of servo data. The controller 30 determines the demodulation timing of various servo data subsequently read by the read head 22r based on the detection timing of the servo marks.

[0039] The Gray code includes a cylinder address for identifying each servo track 41 provided on the magnetic disk 11 and a sector address for identifying each servo sector SV on the servo track 41.

[0040] The burst pattern is pattern data used to detect the amount of deviation from the track center of the servo track 41 indicated by the cylinder address included in the Gray code. The amount of deviation from the track center of the servo track 41 is called the burst offset.

[0041] The post code is data for correcting RRO (Repeatable RunOut).

[0042] The shape of the tracks (data track DTRK and servo track 41) is ideally a perfect circle. However, due to vibrations received during writing of servo data, servo pattern quality, etc., the servo track 41 is distorted. Therefore, the radial position (radial position) of the servo track 41 specified based on the combination of the cylinder address and the burst offset may deviate from the radial position of the servo track 41 with an ideal shape. Since this positional deviation occurs repeatedly in the same manner with the rotation of the magnetic disk 11 (and SPM 12) as a cycle, it is called RRO. The post code is the encoded correction value of this RRO.

[0043] The SoC 30 (for example, the processor 26) corrects the radial position of the magnetic head 22 obtained by the combination of the cylinder address and the burst offset by using the RRO correction value recorded as the post code, thereby obtaining the radial position of the magnetic head 22 with the positional deviation due to RRO canceled. The correction using the RRO correction value is referred to as RRO correction.

[0044] Note that the position where the post code is written is not limited to the servo area SV. The post code may be written in the data area DA or stored in the FROM 28.

[0045] In the manufacturing process of the magnetic disk device 1, measurement of RRO is performed. Ideally, RRO is measured at the position of each data track DTRK finally set. However, measuring RRO for each data track DTRK requires a great deal of time in the manufacturing process. Also, in a hybrid HDD, the position of each data track DTRK can be dynamically changed in the first place, so the position of each data track DTRK cannot be specified in the manufacturing process. To address these issues, in the embodiment, the magnetic disk device 1 is configured to be able to execute a linear RRO correction operation.

[0046] FIG. 3 is a diagram for explaining the linear RRO correction operation according to the embodiment. In this figure, the horizontal axis represents the radial position, and the vertical axis represents the magnitude of RRO. FIG. 3 shows an example of the change in the radial RRO in a certain servo sector SV#n.

[0047] In the manufacturing process, virtual tracks are set at each of a plurality of predetermined radial positions. And for each virtual track, the RRO of the servo sectors included in the virtual track is measured.

[0048] Each virtual track may coincide with the servo track 41, or may be set based on a plurality of servo tracks 41. Each virtual track may be one selected servo track 41 for every predetermined number of servo tracks 41 arranged continuously in the radial direction, or one or more virtual tracks may be set between the servo tracks 41. When the positions of the final plurality of data tracks DTRK are known, each virtual track may coincide with one selected data track DTRK for every predetermined number of data tracks DTRK arranged continuously in the radial direction.

[0049] Hereinafter, each virtual track is denoted as a measurement track MTRK. Note that the radial positions of the plurality of set measurement tracks MTRK are examples of a plurality of first positions.

[0050] The solid curve shown in FIG. 3 indicates the RRO. The plurality of black circles indicate the measured values of the RRO at measurement tracks #k to measurement track #k + 9. From this figure, it can be seen that the measurement positions of the RRO, that is, each measurement track MTRK, are provided discretely in the radial direction.

[0051] In the positioning control using the linear RRO correction operation, the controller 30 obtains the RRO correction value at the position of the magnetic head 22 by linearly interpolating between the measured value of RRO at the measurement track MTRK closest to the magnetic head 22 on the OD side and the measured value of RRO at the measurement track MTRK closest to the magnetic head 22 on the ID side. That is, the dashed-dotted line in FIG. 3 indicates the RRO correction value used by the controller 30 for RRO correction.

[0052] The measured value of RRO at each measurement track MTRK is stored as the RRO correction value at each measurement track MTRK in the servo area SV, FROM 28, or a predetermined position on the magnetic disk 11. The controller 30 executes the linear RRO correction operation using the measured value of RRO at each measurement track MTRK.

[0053] In this way, the controller 30 can perform RRO correction at any position in the radial direction by linear interpolation using the RRO correction values obtained from a plurality of positions discretely set in the radial direction.

[0054] However, in the above-described linear RRO correction operation, the positioning accuracy after linear RRO correction may not be uniform in the radial direction.

[0055] FIG. 4 is a diagram showing the distribution of the positioning accuracy after the linear RRO correction operation of the embodiment. In FIG. 4, the horizontal axis indicates the radial position, and the vertical axis indicates the magnitude of the evaluation index of the positioning accuracy. Hereinafter, the positioning accuracy shall mean the positioning accuracy after the linear RRO correction operation.

[0056] As long as the evaluation index of positioning accuracy corresponds to the positioning accuracy, the evaluation index of positioning accuracy is not limited to specific numerical information. For example, the evaluation index of positioning accuracy may be the standard deviation of the RRO measurement values for one revolution. The evaluation index of positioning accuracy may also be the difference between the maximum value and the minimum value of the RRO measurement values for one revolution. When the standard deviation of the RRO measurement values for one revolution or the difference between the maximum value and the minimum value of the RRO measurement values for one revolution is used as the evaluation index of positioning accuracy, the evaluation index takes a smaller value as the positioning accuracy is better and a larger value as the positioning accuracy is worse.

[0057] As shown in FIG. 4, the positioning accuracy becomes locally the best at the position that coincides with each measurement track MTRK (refer to the vicinity of pes1), and deteriorates according to the distance from the nearest measurement track TRK. And the positioning accuracy becomes locally the worst at the midpoint between two adjacent measurement tracks TRK (refer to the vicinity of pes2).

[0058] The final position of each data track DTRK does not necessarily coincide with any measurement track TRK. Therefore, the positioning operation after the linear RRO correction operation in each data track DTRK varies according to the distance to the nearest measurement track TRK.

[0059] For example, the position of data track DTRK#m + 2 coincides with the position of measurement track MTRK#k + 7, which is the measurement track MTRK closest to data track DTRK#m + 2. There is a slight separation between data track DTRK#m + 3 and measurement track MTRK#k + 8, which is the measurement track MTRK closest to data track DTRK#m + 3. And the distance between data track DTRK#m + 4 and measurement track MTRK#k + 9, which is the measurement track MTRK closest to data track DTRK#m + 4, is larger than the distance between data track DTRK#m + 3 and measurement track MTRK#k + 8, which is the measurement track MTRK closest to data track DTRK#m + 3. Therefore, the positioning accuracy deteriorates in the order of data track DTRK#m + 2, data track DTRK#m + 3, and data track DTRK#m + 4.

[0060] The data track DTRK#m+1 is slightly separated from the measurement track MTRK#k+6 which is the measurement track MTRK closest to the data track DTRK#m+1. And the distance between the data track DTRK#m and the measurement track MTRK#k+5 which is the measurement track MTRK closest to the data track DTRK#m is greater than the distance between the data track DTRK#m+1 and the measurement track MTRK#k+6 which is the measurement track MTRK closest to the data track DTRK#m+1. Therefore, the positioning accuracy deteriorates in the order of the data track DTRK#m+2, the data track DTRK#m+1, and the data track DTRK#m.

[0061] Thus, the positioning accuracy after the linear RRO correction operation in the data track DTRK deteriorates as the distance to the measurement track TRK closest to that data track DTRK becomes longer.

[0062] Hereinafter, the distance between the target data track DTRK and the measurement track MTRK closest to the target data track DTRK will be denoted as the write permission range change determination distance d.

[0063] In order to prevent the data of the data track DTRK adjacent to the target data track DTRK from being erased by overwriting due to the write operation during the write operation, a write permission range is set for the target data track DTRK.

[0064] FIG. 5 is a diagram showing an example of the write permission range of the embodiment. In this figure, the design write range REC is shown for each of the data track DTRK#m-1, the data track DTRK#m, and the data track DTRK#m+1. The write range REC m is the design write range REC for the data track DTRK#m. The write range REC m-1 is the design write range REC for the data track DTRK#m-1. The write range REC m+1is the design write range REC for data track DTRK#m+1. Each write range REC is defined by the element width of write head 22w centered on the track center of data track DTRK.

[0065] Also, in FIG. 5, for each of data track DTRK#m-1, data track DTRK#m, and data track DTRK#m+1, two lines L WOS- ,L WOS+ that define the write permission range are shown. Line L WOS- is a line at a position separated from the track center by WOS in the ID direction side. Line L WOS+ is a line at a position separated from the track center by WOS in the OD direction side.

[0066] Consider that after the write operation for data track DTRK#m, write operations are executed for data track DTRK#m-1 and data track DTRK#m+1. PES m-1 shows an example of the trajectory of magnetic head 22 (more precisely, write head 22w) during the write operation when the write operation for data track DTRK#m-1 is executed. PES m+1 shows an example of the trajectory of magnetic head 22 (more precisely, write head 22w) during the write operation when the write operation for data track DTRK#m+1 is executed.

[0067] In the write operation for data track DTRK#m-1, when it is detected that the position of magnetic head 22 has exceeded the write permission range, the write operation is interrupted. Similarly, in the write operation for data track DTRK#m+1, when it is detected that the position of magnetic head 22 has exceeded the write permission range, the write operation is interrupted. Thus, it is prevented that the data of already written data track DTRK#m is erased by overwriting with the data to be written to data track DTRK#m-1 or data track DTRK#m+1.

[0068] Note that the position of the magnetic head 22 can only be obtained from a plurality of servo regions SV arranged at intervals in the circumferential direction. When the magnetic head 22 is positioned between the servo regions SV, the controller 30 cannot obtain the radial position. Therefore, even if it is confirmed that the position of the magnetic head 22 does not deviate from the write permission range based on the servo data, the radial position of the magnetic head 22 may deviate from the write permission range due to interference or the like in the data region DA. Such a deviation of the position of the magnetic head 22 from the write permission range is called an overrun.

[0069] If the positioning accuracy is poor, the magnetic head 22 may move to a position separated from the track center. In such a case, the amount of overrun increases. Also, if the WOS is made too small with respect to the positioning accuracy, the frequency of interruption of the write operation increases and the write performance deteriorates. Therefore, the WOS is set according to the positioning accuracy.

[0070] However, in the magnetic disk device 1 of the embodiment that performs the linear RRO correction operation, the positioning accuracy may vary for each data track DTRK. In such a case, if an attempt is made to store the set value of the WOS for each data track DTRK, a large-capacity non-volatile storage area is required to store the set value group of the WOS.

[0071] Therefore, according to the embodiment, the controller 30 is configured to dynamically set the WOS according to the write permission range change determination distance d between the data track DTRK of the write target and the measurement track MTRK closest to the data track DTRK of the write target.

[0072] More specifically, the controller 30 stores at least the reference value WOSref of the WOS that is common among a plurality of data tracks DTRK. Then, the controller 30 obtains the change amount dWOS of the WOS based on the write permission range change determination distance d. Then, by changing the reference value WOSref by the change amount dWOS, the set value WOStarget of the WOS of the target data track DTRK is obtained.

[0073] According to the embodiment, the reference value WOSref is individually stored in advance in units larger than one data track DTRK. Therefore, compared with the case of storing the set value group of the WOS for each data track DTRK, it is possible to reduce the capacity of the non-volatile storage area required for storing information regarding the WOS.

[0074] Here, as an example, it is assumed that the reference value WOSref is stored in advance for each area of the TPI and BPI setting units, that is, for each area specified by the head number and the zone number.

[0075] FIG. 6 is a diagram for explaining an example of the functional configuration of the controller 30 according to the embodiment.

[0076] The controller 30 includes a WOS generation unit 31, a WOS setting unit 32, and a dWOS calculation unit 33. Also, in a predetermined storage area, for example, FROM28 or the magnetic disk 11, a WOS reference value group 51 and a dWOS table 52 are stored, and the controller 30 can refer to the WOS reference value group 51 and the dWOS table 52. The controller 30 may load part or all of the WOS reference value group 51 and the dWOS table 52 into the DRAM 29 and refer to this information loaded into the DRAM 29. Note that the storage area in which the WOS reference value group 51 and the dWOS table 52 are stored is an example of a storage device. The WOS is an example of a write permission threshold value.

[0077] The WOS reference value group 51 is information obtained by collecting the reference value WOSref set for each area specified by the head number and the zone number for the entire area of the magnetic disk 11.

[0078] The dWOS table 52 is a table that defines the correspondence relationship between the write permission range change determination distance d and the change amount dWOS. Note that the dWOS table 52 is an example of the first information that defines the correspondence relationship between a plurality of write permission range change determination distances d and a plurality of change amounts dWOS. The form of the first information is not limited to a table. The first information may be a function. A detailed description of the dWOS table 52 will be given later.

[0079] The WOS generation unit 31 acquires the reference value WOSref used in the write operation for the data track DTRK of the write target from the WOS reference value group 51. The WOS generation unit 31 acquires the reference value WOSref based on the head number of the magnetic head 22 that accesses the data track DTRK of the write target and the zone number of the zone to which the data track DTRK of the write target belongs.

[0080] In the following description, the data track DTRK of the write target is referred to as the target data track DTRK. The data track DTRK adjacent to the target data track DTRK is referred to as the adjacent data track DTRK.

[0081] The dWOS calculation unit 33 calculates the write permission range change determination distance d, that is, the distance between the target data track DTRK and the measurement track MTRK closest to the target data track DTRK. The position information of each data track DTRK and the position information of each measurement track MTRK are known. The dWOS calculation unit 33 calculates the write permission range change determination distance d based on the position information of each data track DTRK, the position information of each measurement track MTRK, the cylinder address of the target data track DTRK, and the like. The dWOS calculation unit 33 obtains the change amount dWOS corresponding to the write permission range change determination distance d obtained by calculation by referring to a table that defines the correspondence between the write permission range change determination distance d input from the dWOS table 52 to the dWOS calculation unit 33 and the change amount dWOS.

[0082] The WOS setting unit 32 calculates the set value WOStarget of the WOS of the target data track DTRK based on the reference value WOSref acquired by the WOS generation unit 31 and the change amount dWOS acquired by the dWOS calculation unit 33. Here, as an example, it is assumed that the set value WOStarget is obtained by adding the reference value WOSref and the change amount dWOS.

[0083] FIG. 7 is a diagram showing an example of the relationship between the write permission range change determination distance d and the change amount dWOS defined by the dWOS table 52 of the embodiment. In this figure, the horizontal axis represents the write permission range change determination distance d, and the vertical axis represents the change amount dWOS.

[0084] RROmeasTp is the pitch of the measurement track MTRK. Since the write permission range change determination distance d (exactly the absolute value of the write permission range change determination distance d) is maximized at exactly the middle position between two adjacent measurement tracks MTRK, for the range of the write permission range change determination distance d from -0.5×RROmeasTp to 0.5×RROmeasTp, the correspondence between the write permission range change determination distance d and the change amount dWOS is defined.

[0085] The reference value WOSref is determined based on a predetermined positioning accuracy. In the example shown in FIG. 7, it is assumed that the reference value WOSref is determined based on the positioning accuracy when d = 0. That is, when d = 0, by using the reference value WOSref as the set value WOStarget as it is, even if the magnetic disk device 1 is affected by disturbances such as server rack fan vibration, the data of adjacent data tracks can be guaranteed.

[0086] When the write permission range change determination distance d is different from 0, the positioning accuracy is worse than when d = 0. That is, when the write permission range change determination distance d is different from 0, if the magnetic disk device 1 receives the same disturbance as when d = 0, it is not always possible to guarantee the data of adjacent data tracks. Therefore, as shown in FIG. 7, when the write permission range change determination distance d is different from 0, the change amount dWOS is set to a negative value, and the write permission range is narrowed. This can prevent the data of the adjacent data track DTRK from being erased due to overrun even if the magnetic disk device 1 is affected by a disturbance during the write operation.

[0087] When d = -0.5×RROmeasTp or d = 0.5×RROmeasTp, the positioning accuracy becomes locally the worst. Therefore, the change amount dWOS takes the minimum value.

[0088] Thus, according to the example shown in FIG. 7, the relationship between the write permission range change determination distance d and the change amount dWOS is defined so that the data of adjacent data tracks can be guaranteed regardless of the write permission range change determination distance d.

[0089] FIG. 8 is a diagram showing an example of the relationship between the write permission range change determination distance d and the change amount dWOS defined by the dWOS table 52 of the embodiment. In this figure, the horizontal axis represents the write permission range change determination distance d, and the vertical axis represents the change amount dWOS.

[0090] In the example shown in FIG. 8, when d = 0, the reference value WOSref is determined so as to guarantee not only the data of the adjacent data track but also the write performance.

[0091] When the write permission range change determination distance d is different from 0, the positioning accuracy is worse than when d = 0, and the write performance deteriorates. In order to suppress the deterioration of the write performance, when the write permission range change determination distance d is different from 0, the change amount dWOS takes a positive value. That is, the write permission range is widened. As a result, even if the magnetic disk device 1 receives an external disturbance during the write operation, it is possible to guarantee the write performance.

[0092] When d = -0.5 × RROmeasTp or d = 0.5 × RROmeasTp, the positioning accuracy becomes locally the worst. Therefore, the change amount dWOS takes the maximum value.

[0093] Note that if the write permission range is widened too much, the risk that the data of the adjacent data track DTRK is erased due to an overrun may exceed the allowable level. An upper limit value may be set for the change amount dWOS so that the risk that the data of the adjacent data track DTRK is erased does not exceed the allowable level.

[0094] As described above, according to the example shown in FIG. 8, the relationship between the write permission range change determination distance d and the change amount dWOS is defined so as to guarantee the write performance regardless of the write permission range change determination distance d.

[0095] Subsequently, the operation of the magnetic disk device 1 of the embodiment will be described.

[0096] FIG. 9 is a flowchart showing an example of the operation of the magnetic disk device 1 of the embodiment in the write operation. In the description of this figure, the data track DTRK that is the write target in the write operation is an example of the first data track.

[0097] First, the WOS generation unit 31 acquires a reference value WOSref from the WOS reference value group 51 (S101). The WOS generation unit 31 acquires the reference value WOSref based on the head number indicating the magnetic head 22 accessing the target data track DTRK and the zone number indicating the zone to which the target data track DTRK belongs.

[0098] The dWOS calculation unit 33 calculates the write permission range change determination distance d, that is, the distance between the target data track DTRK and the measurement track MTRK closest to the target data track DTRK (S102).

[0099] FIG. 10 is a diagram for explaining an example of a method for calculating the write permission range change determination distance d.

[0100] In FIG. 10, the position of the data track DTRK at the position (radial position) X is denoted as the data track position X. The data track DTRK at the data track position X shown in this figure is, for example, the p-th data track DTRK in a certain zone. However, p is an integer of 0 or more. The track pitch of the data track DTRK in that zone is denoted as DataTp. Also, assume that the position of the start data track DTRK in that zone is 0 (origin). The data track position X can be expressed by the following formula (1). X = DataTp × p ···(1)

[0101] In FIG. 10, each dotted line indicates the position of the measurement track MTRK. The distance between the origin and the position of the first measurement track MTRK in the zone is denoted as ofs. The position Y of the q-th measurement track MTRK can be expressed by the following formula (2). However, q is an integer of 0 or more. Y = ofs + q × RROmeasTp ···(2)

[0102] The write permission range change determination distance d between the data track DTRK#p at the data track position X and the measurement track MTRK#q closest to the data track DTRK#p is obtained by the following procedure.

[0103] First, the dWOS calculation unit 33 obtains a difference diff by subtracting a distance ofs from the data track position X according to the following formula (3). diff = X - ofs ···(3)

[0104] Subsequently, the dWOS calculation unit 33 subtracts Y from the difference diff. Here, the above-mentioned q is the number of measurement tracks MTRK existing between the data track position 0 and the data track position X, and is equal to the integer part when the difference diff is divided by RROmeasTp. The dWOS calculation unit 33 calculates q and the remainder R according to the following formulas (4) and (5). q = int(diff / RROmeasTp) ···(4) R = diff - k × RROmeasTp ···(5)

[0105] When R is greater than 0.5 × RROmeasTp, the dWOS calculation unit 33 sets the value obtained by subtracting RROmeasTp from the remainder R as the write permission range change determination distance d. When R is less than 0.5 × RROmeasTp, the dWOS calculation unit 33 sets the remainder R as the write permission range change determination distance d. The write permission range change determination distance d calculated in this way is a value in the range from -0.5 × RROmeasTp to 0.5 × RROmeasTp.

[0106] Note that the method described with reference to FIG. 10 is merely an example of a method for calculating the write permission range change determination distance d. Since the positions of each measurement track MTRK, the positions of each data track DTRK, and the position of the target data track DTRK are known, the dWOS calculation unit 33 calculates the write permission range change determination distance d using those known pieces of information. The calculation method can be changed according to the arrangement of each data track DTRK, the arrangement of each measurement track MTRK, and the like.

[0107] Returning to the explanation of FIG. 9, after calculating the write permission range change determination distance d, the dWOS calculation unit 33 refers to the dWOS table 52 to obtain a change amount dWOS corresponding to the write permission range change determination distance d (S103).

[0108] The WOS setting unit 32 calculates the set value WOStarget of the WOS of the target data track DTRK based on the reference value WOSref acquired by the process of S101 and the change amount dWOS acquired by the process of S103 (S104). According to the example described above, the WOS setting unit 32 acquires the set value WOStarget by adding the reference value WOSref and the change amount dWOS.

[0109] The controller 30 executes a write operation on the target data track DTRK using the set value WOStarget (S105). Then, the write operation ends.

[0110] FIG. 11 is a flowchart showing an example of a write operation using the set value WOStarget of the embodiment.

[0111] When the write operation starts (S201), the controller 30 acquires a positioning error when the magnetic head 22 passes through the servo area SV (S202). The controller 30 executes positioning control to position the magnetic head 22 on the target data track DTRK based on servo data. In the positioning control, a linear interpolation using a plurality of RRO correction values obtained by measuring the RRO in a plurality of measurement tracks MTRK is used to acquire the RRO correction value in the target data track DTRK, and an RRO correction operation using the acquired RRO correction value, that is, a linear RRO correction operation, is executed. While executing the positioning control, the controller 30 acquires the deviation amount of the magnetic head 22 from the track center as a positioning error.

[0112] Note that S202 to S205 constitute a loop process. The controller 30 executes this loop process every time the magnetic head 22 passes through the servo area SV.

[0113] After S202, the controller 30 determines whether the absolute value of the positioning error is greater than the set value WOStarget (S203). That is, the controller 30 determines whether the position of the magnetic head 22 deviates from the write permission range.

[0114] If the absolute value of the positioning error is not greater than the set value WOStarget (S203: No), it can be estimated that the position of the magnetic head 22 does not deviate from the write permission range. In that case, the controller 30 executes data writing for the data area DA following the servo area SV that was passed immediately before, to the data area DA (S204). Then, the controller 30 determines whether the writing of all the data to be written to the target data track DTRK has been completed (S205).

[0115] If the writing of all the data to be written to the target data track DTRK has been completed (S205: Yes), the writing operation ends. If the writing of all the data to be written to the target data track DTRK has not been completed yet (S205: No), the control transitions to S202.

[0116] If the absolute value of the positioning error is greater than the set value WOStarget (S203: Yes), it can be estimated that the position of the magnetic head 22 deviates from the write permission range. Therefore, the controller 30 waits for the magnetic disk 11 to make one rotation, holding off on executing the write (S206). When the magnetic disk 11 makes one rotation, the control transitions to S202, and the processing from S202 is executed again.

[0117] In this way, when the position of the magnetic head 22 deviates from the write permission range, the writing operation is interrupted, and when the magnetic head 22 approaches the interruption position of the writing operation again, the processing from S202 is resumed.

[0118] According to the example shown in FIG. 11, when the absolute value of the positioning error is equal to the set value WOStarget, the control transitions to S204 and data writing is executed. The processing when the absolute value of the positioning error is equal to the set value WOStarget is not limited to this. When the absolute value of the positioning error is equal to the set value WOStarget, the control may transition to S206.

[0119] The dWOS table 52 is generated in the manufacturing process. In the manufacturing process, the controller 30 of the magnetic disk device 1 may generate the dWOS table 52 based on dedicated firmware. Alternatively, in the manufacturing process, the magnetic disk device 1 may be connected to a test device, and the test device may generate the dWOS table 52 by controlling the magnetic disk device 1.

[0120] FIG. 12 is a flowchart showing an example of a method for generating the dWOS table 52 of the embodiment. In the description of this figure, it is assumed that the controller 30 generates the dWOS table 52 based on dedicated firmware.

[0121] First, the controller 30 acquires the radial distribution of the positioning accuracy (S301). The controller 30 measures the positioning accuracy at each of a plurality of positions in the radial direction to acquire a radial positioning accuracy distribution as shown in, for example, FIG. 4. In the description of FIG. 12, the positioning accuracy is, for example, the standard deviation of the position error signal for one revolution of the magnetic disk. As long as it is an evaluation index corresponding to the positioning accuracy, the controller 30 can acquire any evaluation index as the positioning accuracy.

[0122] Subsequently, the controller 30 averages the distribution of the positioning accuracy for each of a plurality of intervals delimited by the measurement track MTRK (S302). For example, the controller 30 obtains the distribution in a plurality of intervals by delimiting the radial distribution of the positioning accuracy at each measurement track MTRK, such as the distribution in the interval from measurement track MTRK#0 to measurement track MTRK#1, the distribution in the interval from measurement track MTRK#1 to measurement track MTRK#2. Then, the controller 30 obtains the average of the distribution in the interval delimited by two adjacent measurement tracks MTRK by averaging the distributions in the plurality of intervals.

[0123] Subsequently, the controller 30 generates the dWOS table 52 based on the averaged distribution of the positioning accuracy in the interval delimited by two adjacent measurement tracks MTRK (S303).

[0124] For example, when the controller 30 determines the change amount dWOS with respect to the write permission range change determination distance d so as to be able to guarantee the data of the adjacent data track regardless of the write permission range change determination distance d, a dWOS table 52 that defines the correspondence as shown in FIG. 7 is generated.

[0125] Or, for example, when the controller 30 determines the change amount dWOS with respect to the write permission range change determination distance d so as to be able to guarantee the write performance regardless of the write permission range change determination distance d, a dWOS table 52 that defines the correspondence as shown in FIG. 8 is generated.

[0126] The dWOS table 52 generated by S303 is stored in a predetermined storage area. Then, the operation of generating the dWOS table 52 ends.

[0127] Note that the dWOS table 52 generated in one magnetic disk device 1 may also be used in one or more other magnetic disk devices 1. Or, each magnetic disk device 1 may generate the dWOS table 52 individually. Also, the dWOS table 52 may be generated for each head and zone.

[0128] As described above, according to the embodiment, in the write operation, the controller 30 obtains the RRO correction value on the target data track DTRK by interpolation using the RRO correction values in each of the plurality of measurement tracks MTRK. Then, when positioning the magnetic head 22 on the target data track DTRK, the controller 30 performs RRO correction using the obtained RRO correction value. In the write operation, the controller 30 sets the set value WOStarget based on the write permission range change determination distance d between the target data track DTRK and the measurement track MTRK closest to the target data track DTRK among the plurality of measurement tracks MTRK. The controller 30 performs writing to the target data track DTRK when the positioning error is smaller than the set value WOStarget. The controller 30 refrains from writing to the target data track DTRK when the positioning error is larger than the set value WOStarget.

[0129] Therefore, it is possible to suppress the capacity of the nonvolatile memory area required for storing information regarding WOS. That is, it is possible to suitably set WOS.

[0130] According to the dWOS table 52 shown in FIG. 7, it can be considered that the change amount dWOS of the second value is associated with the write permission range change determination distance d of the first value, and the change amount dWOS of the fourth value smaller than the second value is associated with the write permission range change determination distance d of the third value whose absolute value is larger than the absolute value of the first value.

[0131] By using this dWOS table 52, it is possible to guarantee the data of the adjacent data track regardless of the write permission range change determination distance d.

[0132] Also, when setting WOS using the dWOS table 52 shown in FIG. 7, if the write permission range change determination distance d is the first value, the WOS setting unit 32 sets the fifth value as the set value WOStarget, and if the write permission range change determination distance d is the third value whose absolute value is larger than the absolute value of the first value, a sixth value smaller than the fifth value can be set as the set value WOStarget.

[0133] Therefore, it is possible to guarantee the data of adjacent data tracks regardless of the write permission range change determination distance d.

[0134] Also, according to the dWOS table 52 shown in FIG. 8, it can be considered that a change amount dWOS of the seventh value is associated with the write permission range change determination distance d of the first value, and a change amount dWOS of the eighth value larger than the seventh value is associated with the write permission range change determination distance d of the third value whose absolute value is larger than the absolute value of the first value.

[0135] By using this dWOS table 52, it is possible to guarantee the write performance regardless of the write permission range change determination distance d.

[0136] Also, when setting WOS using the dWOS table 52 shown in FIG. 8, if the write permission range change determination distance d is the first value, the WOS setting unit 32 sets the ninth value as the set value WOStarget, and if the write permission range change determination distance d is the third value whose absolute value is larger than the absolute value of the first value, a tenth value larger than the ninth value can be set as the set value WOStarget.

[0137] Therefore, it is possible to guarantee the write performance regardless of the write permission range change determination distance d.

[0138] Also, as described with reference to FIG. 12, the controller 30 evaluates the positioning error at an arbitrary radial position and generates the dWOS table 52 based on the positioning accuracy measured in a plurality of intervals delimited by a plurality of RRO measurement positions.

[0139] By using the dWOS table 52 generated in this way, the controller 30 can suitably set the WOS.

[0140] Although several embodiments of the present invention have been described, these embodiments are presented by way of example 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.

Explanation of Reference Numerals

[0141] 1 Magnetic disk device, 2 Host, 11 Magnetic disk, 13 Lamp, 15 Actuator arm, 16 VCM, 21 SVC, 22 Magnetic head, 22r Read head, 22w Write head, 23 HDC, 24 Preamplifier, 25 RWC, 26 Processor, 28 FROM, 29 DRAM, 30 Controller, 31 WOS generation unit, 32 WOS setting unit, 33 dWOS calculation unit, 41 Servo track, 51 WOS reference value group, 52 dWOS table.

Claims

1. A magnetic head and, A magnetic disk having a plurality of data tracks, In a write operation for one of the plurality of data tracks using the magnetic head, A second RRO correction value, which is an RRO correction value at a second position, is obtained by interpolation using a plurality of first RRO correction values obtained by measuring RRO (Repeatable RunOut) at each of the plurality of first positions. The plurality of first positions are a plurality of radial positions in the radial direction of the magnetic disk, and the second position is the position of a first data track, which is the one data track, When positioning the magnetic head on the first data track, RRO correction using the second RRO correction value is performed, A write permission threshold is set based on a write permission range change determination distance, which is the distance between the first position closest to the second position among the plurality of first positions and the second position, When the positioning error of the first data track is smaller than the write permission threshold, writing to the first data track is performed, When the positioning error of the first data track is larger than the write permission threshold, writing to the first data track is withheld, A controller, A magnetic disk device comprising the same.

2. The controller, When the absolute value of the write permission range change determination distance is a first value, sets the second value as the write permission threshold, When the absolute value of the write permission range change determination distance is a third value larger than the first value, sets a fourth value smaller than the second value as the write permission threshold, The magnetic disk device according to Claim 1.

3. The controller, When the absolute value of the write permission range change determination distance is a first value, sets the second value as the write permission threshold, When the absolute value of the write permission range change determination distance is a third value larger than the first value, sets a fourth value larger than the second value as the write permission threshold, The magnetic disk device according to Claim 1.

4. The magnetic disk device further comprises a storage device that stores a reference value of the write permission threshold, and first information that defines a correspondence relationship between a plurality of values of the write permission range change determination distance and a change amount of a plurality of values of the write permission threshold. The controller obtains a change amount of a write permission threshold corresponding to the write permission range change determination distance based on the first information, and obtains the write permission threshold based on a reference value of the write permission threshold and the obtained change amount of the write permission threshold. The magnetic disk device according to claim 1.

5. When the absolute value of the write permission range change determination distance is a first value, the first information associates a first write permission threshold change amount, and when the absolute value of the write permission range change determination distance is a third value greater than the first value, a second write permission threshold change amount smaller than the first write permission threshold change amount is associated. The controller obtains the write permission threshold by adding the reference value of the write permission threshold and the obtained change amount of the write permission threshold. The magnetic disk device according to claim 4.

6. When the absolute value of the write permission range change determination distance is a first value, the first information associates a first write permission threshold change amount, and when the absolute value of the write permission range change determination distance is a third value greater than the first value, a second write permission threshold change amount greater than the first write permission threshold change amount is associated. The controller obtains the write permission threshold by adding the reference value of the write permission threshold and the obtained change amount of the write permission threshold. The magnetic disk device according to claim 4.

7. The controller evaluates a positioning error at an arbitrary radial position, and generates the first information based on positioning accuracy measured in a plurality of intervals delimited by the plurality of first positions. The magnetic disk device according to claim 4.

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