Magnetic disk device

Abstract

According to one embodiment, it is generally directed to providing a magnetic disk device capable of appropriately setting a WOS. According to one embodiment, a controller of a magnetic disk device acquires an RRO correction value for performing RRO correction at a position of a target data track by using interpolation using a plurality of RRO correction values obtained by measurement of RRO at each of a plurality of first positions during write operation. During the write operation, the controller sets the WOS on the basis of an allowable write range change determination distance that is the distance between the target data track and a first position closest to the target data track among the plurality of first positions.

Description

[0001] This application claims the benefit of priority from Japanese Patent Application No. 2023-216541, filed on December 22, 2023, the entire contents of which are incorporated herein by reference. Technical Field

[0002] This embodiment generally relates to a disk device. Background Art

[0003] In a write operation in a disk device, a write permission range centered on the center of a track is set in the radial direction. Then, when the position of the magnetic head is within the write permission range, the disk device performs writing. When the position of the magnetic head is outside the write permission range, the disk device suppresses writing. The disk device determines whether the position of the magnetic head is within the write permission range or outside the write permission range based on a comparison between the positioning error with respect to the data track to be written 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. Summary of the Invention

[0004] One embodiment is a disk device including: a magnetic head; a disk having a plurality of data tracks; and a controller. In a write operation for one data track among the plurality of data tracks using the magnetic head, the controller obtains a second RRO correction value as an RRO correction value at a second position by interpolation using a plurality of first RRO correction values obtained by measuring the repeatable runout (RRO) at each of a plurality of first positions. The plurality of first positions are a plurality of radial positions in the radial direction of the disk, and the second position is the position of a first data track as the one data track. When positioning the magnetic head on the first data track, the controller performs correction of the RRO using the second RRO correction value, sets a write permission threshold based on a write permission range change determination distance, which is the distance between the nearest first position among the plurality of first positions and the second position, and performs writing for the first data track when the positioning error of the first data track is smaller than the write permission threshold, and suppresses writing for the first data track when the positioning error of the first data track is larger than the write permission threshold.

[0005] According to one embodiment, it is possible to provide a disk device capable of appropriately setting WOS. Brief Description of the Drawings

[0006] Figure 1 It is a schematic diagram showing an example of the configuration of a disk device according to an embodiment.

[0007] Figure 2 It is a schematic diagram showing an example of the configuration of a disk according to an embodiment.

[0008] Figure 3 It is a diagram for explaining the linear RRO correction operation according to an embodiment.

[0009] Figure 4 It is a diagram showing the distribution of the positioning accuracy after the linear RRO correction operation according to an embodiment.

[0010] Figure 5 It is a diagram showing an example of the allowable write range according to an embodiment.

[0011] Figure 6 It is a diagram for explaining an example of the functional configuration of a controller according to an embodiment.

[0012] Figure 7 It is a diagram showing an example of the relationship between the allowable write range change determination distance d and the change amount dWOS defined by the dWOS table according to an embodiment.

[0013] Figure 8 It is a diagram showing an example of the relationship between the allowable write range change determination distance d and the change amount dWOS defined by the dWOS table according to an embodiment.

[0014] Figure 9 It is a flowchart showing an example of the operation of a disk device according to an embodiment during a write operation.

[0015] Figure 10 It is a diagram for explaining an example of the calculation method of the allowable write range change determination distance d.

[0016] Figure 11 It is a flowchart showing an example of a write operation using the set value WOS according to an embodiment target of an embodiment.

[0017] Figure 12 It is a flowchart showing an example of the generation method of the dWOS table according to an embodiment.

[0018] Reference Numeral Explanation

[0019] 1 Disk device, 2 Host, 11 Disk, 13 Ramp, 15 Actuator arm, 16 VCM, 21 SVC, 22 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. Detailed implementation mode

[0020] Hereinafter, with reference to the accompanying drawings, the disk device according to the embodiment will be described in detail. In addition, the present invention is not limited by this embodiment.

[0021] (Embodiment)

[0022] Figure 1 It is a schematic diagram showing an example of the configuration of the disk device 1 of the embodiment.

[0023] The disk device 1 is connected to the host 2. The disk device 1 can receive access commands from the host 2. The access commands include write commands and read commands.

[0024] The disk device 1 includes a disk 11 having a magnetic layer formed on its surface. The disk device 1 accesses the disk 11 according to the access command. The access includes writing of data and reading of data.

[0025] Writing and reading of data are performed by the head 22. Specifically, in addition to the disk 11, the disk device 1 further 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 head 22, a hard disk controller (HDC) 23, a preamplifier 24, a read / write channel (RWC) 25, a processor 26, a FROM (Flash ReadOnly Memory) 28, and a DRAM (Dynamic Random Access Memory) 29.

[0026] The disk 11 rotates at a predetermined rotational speed by the coaxially mounted SPM 12.

[0027] 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.

[0028] The head 22 writes to and reads from the disk 11 through the write head 22w and the read head 22r it has. Additionally, the head 22 is installed at the front end of the actuator arm 15. The head 22 moves in the radial direction of the disk 11 through the VCM 16 driven by the SVC 21. Furthermore, one or both of the write head 22w and the read head 22r provided in the head 22 can be provided in multiple numbers with respect to a single head 22.

[0029] When the disk 11 stops rotating or the like, the head 22 moves onto the ramp 13. The ramp 13 is configured to hold the head 22 at a position separated from the disk 11.

[0030] The preamplifier 24 is an integrated circuit that writes and reads data via the head 22. During the read operation, the preamplifier 24 amplifies and outputs the signal read from the disk 11 by the head 22 and supplies it to the RWC 25. Additionally, during the write operation, the preamplifier 24 amplifies the signal corresponding to the data to be written provided from the RWC 25 and supplies it to the head 22.

[0031] The HDC 23 controls the transmission and reception of data between it and the host 2 via the I / F bus, as well as controls the DRAM 29 and the like.

[0032] The DRAM 29 is used as a buffer for data transmitted and received between the host 2. For example, the DRAM 29 is used to temporarily store the data to be written or the data read from the disk 11.

[0033] Additionally, the DRAM 29 is used by the processor 26 as a working memory. The DRAM 29 is used as an area for loading the firmware program and an area for temporarily storing various management data.

[0034] The RWC 25 modulates the data to be written provided from the HDC 23 and supplies it to the preamplifier 24. Additionally, the RWC 25 performs demodulation including error correction on the signal read from the disk 11 and supplied from the preamplifier 24, and then outputs the signal as digital data to the HDC 23.

[0035] 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.

[0036] The firmware program and various setting information and the like are stored in the FROM 28. Additionally, the firmware program can also be stored in the disk 11.

[0037] The processor 26 controls the entire disk device 1 according to the firmware program stored in the FROM 28 or the disk 11. For example, the processor 26 loads the firmware program from the FROM 28 or the disk 11 into the DRAM 29, and controls the SVC 21, the preamplifier 24, the RWC 25, the HDC 23, etc. according to the firmware program loaded into the DRAM 29.

[0038] In addition, part or all of the functions of the processor 26 can also be implemented by hardware circuits such as FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

[0039] 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. In addition to these, the SoC 30 may further include other elements (such as the FROM 28, or the DRAM 29, etc.). In addition, the SoC 30 is an example of a controller.

[0040] In addition, Figure 1 One disk 11 is shown in the figure. However, the disk device 1 may include multiple disks 11. When the disk device 1 includes multiple disks 11, the multiple disks 11 are integrally rotated by the SPM 12.

[0041] In addition, when the number of disks 11 included in the disk device 1 is N, the number of recording surfaces on which data can be written is 2N (N is an integer of 1 or more). In order to access the 2N recording surfaces, the disk device 1 includes 2N magnetic heads 22 that respectively access different recording surfaces. It is assumed that the 2N magnetic heads 22 are identified by magnetic head numbers.

[0042] Figure 2 It is a schematic diagram showing an example of the configuration of the disk 11 of the embodiment.

[0043] In addition, in this figure, the radial direction, the circumferential direction, the inner diameter (Inner Diameter: ID) direction, and the outer diameter (Outer Diameter: OD) direction are shown. In the radial direction, the direction from the edge of the disk 11 toward the center is the inner diameter (Inner Diameter: ID) direction, and the direction from the center of the disk 11 toward the edge is the outer diameter (Outer Diameter: OD) direction.

[0044] In a manufacturing process, servo data for positioning the magnetic head 22 is written to the disk 11, for example, by a servo writer or by self-servo writing (SSW). According to Figure 2 , as an example of the configuration of the servo area where the servo data is written, a plurality of servo areas SV are formed, which are radially arranged in the radial direction and spaced apart at a predetermined interval in the circumferential direction. Between two servo areas SV that are continuous in the circumferential direction, a data area DA for writing data is arranged.

[0045] A plurality of concentric servo tracks 41 are provided in the radial direction of the disk 11. In addition, a plurality of data tracks (denoted as data track DTRK) are set on the surface where the plurality of servo tracks 41 are provided.

[0046] There are variations in the recording performance of each magnetic head 22 due to manufacturing deviations. In addition, there are also variations in the data holding capacity on the recording surface of the disk 11. Thus, in one example, the recording surface is divided into a plurality of zones in the radial direction, and for each combination of the zone and the magnetic head 22, the configuration density of the data track DTRK and the recording density of the data along the data track DTRK are determined. That is, the track pitch of the data track DTRK can be different for each zone and each recording surface. In addition, the configuration density of the data track DTRK is referred to as TPI (Track Per Inch), and the recording density of the data along the data track DTRK is referred to as BPI (Bit Per Inch).

[0047] In addition, as a configuration 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 configured 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 disk 11 is written overlapping a part of the data of the other data track DTRK of the two data tracks DTRK. According to the SMR method, the track pitch of the data track DTRK is narrower than the width (WHw) of the write head 22w of the magnetic head 22, and thus a higher recording density can be obtained compared with the CMR method. However, according to the SMR method, the random write performance is lower than that of the CMR method.

[0048] The configuration of the data track DTRK can be fixed to the CMR mode or the SMR mode, or can be dynamically changed between the CMR mode and the SMR mode. For example, the disk device 1 can be configured to change the configuration of the data track DTRK between the CMR mode and the SMR mode for a part or all of the recording surface based on an instruction from the user. In addition, a hard disk device capable of changing the configuration of the data track DTRK between the CMR mode and the SMR mode is called a hybrid HDD (Hard Disk Drive).

[0049] The disk device 1 stores settings of the positional relationships between a plurality of servo tracks 41 and each data track DTRK. The disk device 1 performs control (referred to as positioning control) for positioning the head 22 at a target data track DTRK based on servo data recorded in the servo area SV. The positioning control includes a seek operation which is an operation for moving the head 22 toward the target data track DTRK in the radial direction, and a tracking operation for maintaining the head 22 on the target data track DTRK, etc.

[0050] The servo data can include a preamble, a servo mark, a Gray code, a burst pattern, and a postamble.

[0051] The preamble is a single-cycle pattern data that periodically changes in the circumferential direction. The preamble is used for adjusting the amplitude, phase, and frequency of the sampled data when the servo waveform read by the read head 22r is taken into the RWC25 based on the servo clock.

[0052] The servo mark is pattern data for determining the demodulation timing of the servo data. The controller 30 determines the demodulation timing of various servo data read by the read head 22r later based on the detection timing of the servo mark.

[0053] The Gray code includes a cylinder address for identifying each servo track 41 provided on the disk 11 and a sector address for identifying each servo sector SV on the servo track 41.

[0054] The burst pattern is pattern data for detecting the position offset of the servo track 41 represented by the cylinder address included in the Gray code with respect to the track center. The position offset of the servo track 41 with respect to the track center is called a burst offset.

[0055] The postamble is data for correcting RRO (Repeatable RunOut).

[0056] For the shape of the tracks (data track DTRK and servo track 41), a perfect circle is ideal. However, due to vibrations during servo data writing, servo pattern quality, etc., the servo track 41 becomes skewed. As a result, the position in the radial direction (radial position) of the servo track 41 determined based on the combination of the cylinder address and the burst offset sometimes deviates from the radial position of the servo track 41 with an ideal shape. Since this deviation occurs repeatedly at a cycle of one rotation of the magnetic disk 11 (and SPM 12), it is called RRO. The postcode is obtained by encoding the correction value for this RRO.

[0057] The SoC 30 (e.g., the processor 26) corrects the radial position of the head 22 obtained from the combination of the cylinder address and the burst offset by using the RRO correction value recorded as the postcode, and obtains the radial position of the head 22 with the position deviation caused by RRO eliminated. The correction using the RRO correction value is referred to as RRO correction.

[0058] In addition, the position where the postcode is written is not limited to the servo area SV. The postcode can be written into the data area DA or stored in the FROM 28.

[0059] In the manufacturing process of the disk device 1, the RRO is measured. Ideally, the RRO is measured at the finally set position of each data track DTRK. However, when measuring the RRO for each data track DTRK, the manufacturing process requires a lot of time. In addition, in a hybrid HDD, since the positions of the respective data tracks DTRK can originally change dynamically, the positions of the respective data tracks DTRK cannot be determined in the manufacturing process. To address this, in the embodiment, the disk device 1 is configured to be able to execute a linear RRO correction operation.

[0060] Figure 3 FIG. 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 the RRO. Figure 3 shows an example of the change in the radial RRO in a certain servo sector SV#n.

[0061] In the manufacturing process, virtual tracks are set at each of a plurality of predetermined radial positions. And in each virtual track, the RRO of the servo sectors included in the virtual track is measured.

[0062] Each virtual track can either coincide with the servo track 41 or be set based on multiple servo tracks 41 as a reference. Each virtual track can either be one servo track 41 selected for every predetermined number of servo tracks 41 continuously arranged in the radial direction or one or more virtual tracks can be set between the servo tracks 41. When the positions of the final multiple data tracks DTRK are known, each virtual track can coincide with one data track DTRK selected for every predetermined number of data tracks DTRK continuously arranged in the radial direction.

[0063] Hereinafter, each virtual track is denoted as the measurement track MTRK. In addition, the radius positions of the multiple set measurement tracks MTRK are an example of multiple first positions.

[0064] Figure 3 The solid curve shown represents the RRO. The multiple black circles represent the measured values of the RRO in the measurement track #k to the measurement track #k + 9. From this figure, it can be seen that the measurement positions of the RRO, that is, the respective measurement tracks MTRK are discretely arranged in the radial direction.

[0065] In the positioning control using the linear RRO correction operation, the controller 30 obtains the RRO correction value at the position of the head 22 by linearly interpolating between the measured value of the RRO in the measurement track MTRK closest to the head 22 on the OD side and the measured value of the RRO in the measurement track MTRK closest to the head 22 on the ID side. That is, Figure 3 The dotted line of represents the RRO correction value used by the controller 30 in the correction of the RRO.

[0066] The measured value of the RRO in each measurement track MTRK is stored as the RRO correction value in each measurement track MTRK at a predetermined position in the servo area SV, FROM28, or the disk 11. The controller 30 uses the measured value of the RRO in each measurement track MTRK to perform the linear RRO correction operation.

[0067] In this way, the controller 30 can perform the RRO correction at an arbitrary position in the radial direction by using the linear interpolation of the RRO correction values obtained from the multiple positions discretely set in the radial direction.

[0068] However, in the above linear RRO correction operation, the positioning accuracy after the linear RRO correction is sometimes uneven in the radial direction.

[0069] Figure 4 is a diagram showing the distribution of the positioning accuracy after the linear RRO correction operation of the embodiment. In Figure 4In this figure, the horizontal axis represents the radius position, and the vertical axis represents the magnitude of the evaluation index of the positioning accuracy. In addition, hereinafter, the positioning accuracy means the positioning accuracy after the linear RRO correction operation.

[0070] As long as the evaluation index of the positioning accuracy corresponds to the positioning accuracy, the evaluation index of the positioning accuracy is not limited to specific numerical information. For example, the evaluation index of the positioning accuracy can also be the standard deviation of the RRO measurement value for one week. The evaluation index of the positioning accuracy can also be the difference between the maximum value and the minimum value of the RRO measurement value for one week. When the standard deviation of the RRO measurement value for one week and the difference between the maximum value and the minimum value of the RRO measurement value for one week are used as the evaluation index of the positioning accuracy, for this evaluation index, the better the positioning accuracy, the smaller the value, and the worse the positioning accuracy, the larger the value.

[0071] As Figure 4 shown, the positioning accuracy is locally optimal at the position consistent 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 is locally the worst at the midpoint between two adjacent measurement tracks TRK (refer to the vicinity of pes2).

[0072] The position of each final 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 has a deviation according to the distance to the nearest measurement track TRK.

[0073] For example, the position of the data track DTRK#m + 2 coincides with the position of the measurement track MTRK#k + 7, which is the measurement track MTRK closest to the data track DTRK#m + 2. The data track DTRK#m + 3 and the measurement track MTRK#k + 8, which is the measurement track MTRK closest to the data track DTRK#m + 3, are separated by some distance. And the distance between the data track DTRK#m + 4 and the measurement track MTRK#k + 9, which is the measurement track MTRK closest to the data track DTRK#m + 4, is larger than the distance between the data track DTRK#m + 3 and the measurement track MTRK#k + 8, which is the measurement track MTRK closest to the data track DTRK#m + 3. Therefore, in the order of the data track DTRK#m + 2, the data track DTRK#m + 3, and the data track DTRK#m + 4, the positioning accuracy deteriorates.

[0074] The data track DTRK#m+1 is separated from the measurement track MTRK#k+6 which is the measurement track MTRK closest to the data track DTRK#m+1. Also, 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 larger 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.

[0075] Thus, for the positioning accuracy after the linear RRO correction operation for the data track DTRK, the longer the distance to the measurement track TRK closest to the data track DTRK, the worse it becomes.

[0076] In addition, hereinafter, the distance between the target data track DTRK and the measurement track MTRK closest to the target data track DTRK is denoted as the allowable write range change determination distance d.

[0077] In order to prevent the data of the data track DTRK adjacent to the target data track DTRK from being erased by overwriting based on the write operation, an allowable write range is set for the target data track DTRK.

[0078] Figure 5 FIG. is an example showing the allowable write range of the embodiment. In this figure, the design write ranges REC are 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 related to the data track DTRK#m. The write range REC m-1 is the design write range REC related to the data track DTRK#m-1. The write range REC m+1 is the design write range REC related to the data track DTRK#m+1. Each write range REC is defined by the element width of the write head 22w centered on the track center of the data track DTRK.

[0079] In addition, Figure 5 in, two lines L defining the allowable write range are shown for each of the data track DTRK#m-1, the data track DTRK#m, and the data track DTRK#m+1 WOS- 、L WOS+ . The line L WOS- is a line at a position where it is separated from the track center by WOS toward the ID direction side. The line L WOS+It is a line at a position that has moved away from the WOS from the center of the track toward the OD direction side.

[0080] Consider performing a write operation on data track DTRK#m - 1 and data track DTRK#m + 1 after the write operation on data track DTRK#m. PES m-1 An example of the track of the head 22 (more precisely, the write head 22w) during the write operation when performing the write operation on data track DTRK#m - 1. PES m+1 An example of the track of the head 22 (more precisely, the write head 22w) during the write operation when performing the write operation on data track DTRK#m + 1.

[0081] During the write operation on data track DTRK#m - 1, when it is detected that the position of the head 22 has exceeded the allowable write range, the write operation is interrupted. Similarly, during the write operation on data track DTRK#m + 1, when it is detected that the position of the head 22 has exceeded the allowable write range, the write operation is interrupted. Thus, it is possible to prevent the data on the already written data track DTRK#m from being erased by overwriting with the data on data track DTRK#m - 1 and data track DTRK#m + 1.

[0082] In addition, the position of the head 22 can only be obtained from a plurality of servo regions SV arranged at intervals in the circumferential direction. When the head 22 is located between the servo regions SV, the controller 30 cannot obtain the radius position. Thus, even if it is confirmed based on the servo data that the position of the head 22 has not deviated from the allowable write range, in the data area DA, the radius position of the head 22 may deviate from the allowable write range due to external interference or the like. Such a situation where the position of the head 22 deviates from the allowable write range is called overrun.

[0083] When the positioning accuracy is poor, the head 22 sometimes moves at a position away from the center of the track. In such a case, the amount of overrun becomes larger. In addition, if the WOS is made too small relative to the positioning accuracy, the frequency of interruption of the write operation becomes high and the write performance decreases. Thus, the WOS is set according to the positioning accuracy.

[0084] However, in the 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 it is desired 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.

[0085] Accordingly, according to the embodiment, the controller 30 is configured to dynamically set the WOS according to the write target data track DTRK and the allowable write range change determination distance d of the measurement track MTRK closest to the write target data track DTRK.

[0086] More specifically, the controller 30 stores at least a reference value WOSref of the WOS common to a plurality of data tracks DTRK. Further, the controller 30 obtains a change amount dWOS of the WOS based on the allowable write range change determination distance d. Then, by changing the reference value WOSref by the change amount dWOS, a set value WOS of the WOS for the target data track DTRK is obtained. target 。

[0087] According to the embodiment, the reference value WOSref is stored in advance individually in units larger than one data track DTRK. Therefore, compared with the case where the set value group of the WOS is stored for each data track DTRK, the capacity of the non-volatile storage area required for storing information related to the WOS can be reduced.

[0088] Here, as an example, it is assumed that the reference value WOSref is stored in advance for each area of the set units of TPI and BPI, that is, for each area determined by the head number and the zone number.

[0089] Figure 6 FIG. is an example of the functional configuration of the controller 30 for explaining the embodiment.

[0090] The controller 30 includes a WOS generation unit 31, a WOS setting unit 32, and a dWOS calculation unit 33. In addition, a WOS reference value group 51 and a dWOS table 52 are stored in a predetermined storage area, such as FROM28 or the disk 11, and the controller 30 can refer to the WOS reference value group 51 and the dWOS table 52. The controller 30 may also load a 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. In addition, the storage area storing the WOS reference value group 51 and the dWOS table 52 is an example of a storage device. The WOS is an example of an allowable write threshold.

[0091] The WOS reference value group 51 is information obtained by collecting the reference value WOSref set for each area determined by the head number and the zone number in the amount of the entire area of the disk 11.

[0092] The dWOS table 52 is a table that defines the correspondence between the allowable write range change determination distance d and the change amount dWOS. In addition, the dWOS table 52 is an example of the first information that defines the correspondence between the allowable write range change determination distances d for multiple values and the change amounts dWOS for multiple values. The form of the first information is not limited to a table. The first information may also be a function. A detailed description of the dWOS table 52 will be given below.

[0093] The WOS generation unit 31 obtains the reference value WOSref used in the write operation on the data track DTRK of the write target from the WOS reference value group 51. The WOS generation unit 31 obtains the reference value WOSref based on the head number of the head 22 accessing 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.

[0094] In the following description, the data track DTRK of the write target is denoted as the target data track DTRK. The data track DTRK adjacent to the target data track DTRK is denoted as the adjacent data track DTRK.

[0095] The dWOS calculation unit 33 calculates the allowable write range change determination distance d, that is, the distance between the target data track DTRK and the nearest measurement track MTRK. 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 allowable write 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, etc. The dWOS calculation unit 33 inputs the change amount dWOS corresponding to the calculated allowable write range change determination distance d from the dWOS table 52 into the dWOS calculation unit 33, and obtains the correspondence between the allowable write range change determination distance d and the change amount dWOS by referring to the table that defines the correspondence between the allowable write range change determination distance d and the change amount dWOS.

[0096] The WOS setting unit 32 calculates the set value WOS of the WOS of the target data track DTRK based on the reference value WOSref obtained by the WOS generation unit 31 and the change amount dWOS obtained by the dWOS calculation unit 33 target . Here, as an example, it is assumed that the set value WOS target is obtained by adding the reference value WOSref and the change amount dWOS.

[0097] Figure 7It is a diagram showing an example of the relationship between the allowable write range change determination distance d specified in the dWOS table 52 of the embodiment and the change amount dWOS. In this diagram, the horizontal axis represents the allowable write range change determination distance d, and the vertical axis represents the change amount dWOS.

[0098] RROmeasTp is the pitch of the measured track MTRK. The allowable write range change determination distance d (accurately speaking, the absolute value of the allowable write range change determination distance d) is the largest at exactly the middle position between two adjacent measured tracks MTRK. Therefore, for the range of the allowable write range change determination distance d from -0.5×RROmeasTp to 0.5×RROmeasTp, the corresponding relationship between the allowable write range change determination distance d and the change amount dWOS is specified.

[0099] The reference value WOSref is determined based on a predetermined positioning accuracy. In Figure 7 the example shown, it is set to determine the reference value WOSref based on the positioning accuracy when d = 0. That is, when d = 0, by directly using the reference value WOSref as the set value WOS target and using it, even if the disk device 1 is subjected to external disturbances such as the vibration of the server rack fan, the data of adjacent data tracks can be guaranteed.

[0100] When the allowable write range change determination distance d is different from 0, the positioning accuracy is worse than the case when d = 0. That is, when the allowable write range change determination distance d is different from 0, if the disk device 1 is subjected to the same external disturbance as the case when d = 0, the data of adjacent data tracks may not necessarily be guaranteed. Therefore, as Figure 7 shown, when the allowable write range change determination distance d is different from 0, the change amount dWOS is set to a negative value, and the allowable write range becomes narrower. Thus, even if the disk device 1 is subjected to external disturbances during the write operation, it is possible to prevent the data of adjacent data tracks DTRK from being erased due to overrun.

[0101] When d = -0.5×RROmeasTp or d = 0.5×RROmeasTp, the positioning accuracy is locally the worst. Therefore, the change amount dWOS takes the minimum value.

[0102] In this way, according to Figure 7 the example shown, the relationship between the allowable write range change determination distance d and the change amount dWOS is specified so that the data of adjacent data tracks can be guaranteed regardless of the allowable write range change determination distance d.

[0103] Figure 8This is a diagram showing an example of the relationship between the allowable write range change determination distance d and the change amount dWOS specified by the dWOS table 52 of the embodiment. In this diagram, the horizontal axis represents the allowable write range change determination distance d, and the vertical axis represents the change amount dWOS.

[0104] In Figure 8 the example shown, when d = 0, the reference value WOSref is determined in such a way that not only the data of adjacent data tracks can be guaranteed, but also the write performance can be guaranteed.

[0105] When the allowable write range change determination distance d is different from 0, compared with the case of d = 0, the positioning accuracy is poor and the write performance is reduced. In order to suppress the reduction of the write performance, when the allowable write range change determination distance d is different from 0, the change amount dWOS takes a positive value. That is, the allowable write range is extended. Thus, even if the disk device 1 is subjected to external interference during the write operation, the write performance can be guaranteed.

[0106] 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.

[0107] In addition, if the allowable write range is overly extended, there may be a risk that the risk of erasing the data of the adjacent data track DTRK due to overrun exceeds the allowable level. An upper limit value can also be set for the change amount dWOS so that the risk of erasing the data of the adjacent data track DTRK does not exceed the allowable level.

[0108] In this way, according to Figure 8 the example shown, the relationship between the allowable write range change determination distance d and the change amount dWOS can be specified in such a way that the write performance can be guaranteed regardless of the allowable write range change determination distance d.

[0109] Next, the operation of the disk device 1 of the embodiment will be described.

[0110] Figure 9 This is a flowchart showing an example of the operation of the disk device 1 of the embodiment during the write operation. In addition, in the description of this diagram, the write target data track DTRK during the write operation is an example of the first data track.

[0111] First, the WOS generation unit 31 obtains the reference value WOSref from the WOS reference value group 51 (S101). The WOS generation unit 31 obtains the reference value WOSref based on the head number of the head 22 representing the access to the target data track DTRK and the zone number of the zone to which the target data track DTRK belongs.

[0112] The dWOS calculation unit 33 calculates the allowable write 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).

[0113] Figure 10 It is a diagram for explaining an example of the calculation method of the allowable write range change determination distance d.

[0114] In Figure 10 , the position of the data track DTRK at the position (radial position E) 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 area. Here, p is an integer of 0 or more. The track pitch of the data track DTRK in this area is denoted as DataTp. In addition, the position of the start data track DTRK in this area is assumed to be 0 (origin). The data track position X is represented by the following formula (1).

[0115] X = DataTp × p...(1)

[0116] In Figure 10 , each dashed line represents the position of the measurement track MTRK. The distance between the origin and the position of the first measurement track MTRK in the area is denoted as ofs. The position Y of the q-th measurement track MTRK is represented by the following formula (2). Here, q is an integer of 0 or more.

[0117] Y = ofs + q × RROmeasTp...(2)

[0118] The allowable write 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 steps.

[0119] First, the dWOS calculation unit 33 obtains the difference diff obtained by subtracting the distance ofs from the data track position X according to the following formula (3).

[0120] diff = X - ofs...(3)

[0121] Next, the dWOS calculation unit 33 subtracts Y from the difference diff. Here, the above 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).

[0122] q = int(diff / RROmeasTp)...(4)

[0123] R = diff - k × RROmeasTp…(5)

[0124] When R is greater than 0.5 × RROmeasTp, the dWOS calculation unit 33 uses the value obtained by subtracting RROmeasTp from the remainder R as the allowable write range change determination distance d. When R is less than 0.5 × RROmeasTp, the dWOS calculation unit 33 uses the remainder R as the allowable write range change determination distance d. The calculated allowable write range change determination distance d is a value within the range of -0.5 × RROmeasTp to 0.5 × RROmeasTp.

[0125] In addition, the method described Figure 10 is just an example of the calculation method of the allowable write range change determination distance d. Since the positions of the respective measurement tracks MTRK, the positions of the respective data tracks DTRK, and the position of the target data track DTRK are known, the dWOS calculation unit 33 uses this known information to calculate the allowable write range change determination distance d. This calculation method can be changed according to the configuration of the respective data tracks DTRK, the configuration of the respective measurement tracks MTRK, etc.

[0126] Returning the explanation to Figure 9 After calculating the allowable write range change determination distance d, the dWOS calculation unit 33 obtains the change amount dWOS corresponding to the allowable write range change determination distance d by referring to the dWOS table 52 (S103).

[0127] The WOS setting unit 32 calculates the set value WOS of the WOS of the target data track DTRK based on the reference value WOSref obtained through the process of S101 and the change amount dWOS obtained through the process of S103 target (S104). According to the example described above, the WOS setting unit 32 obtains the set value WOS by adding the reference value WOSref and the change amount dWOS target .

[0128] The controller 30 uses the set value WOS target to perform the write operation on the target data track DTRK (S105). Then, the write operation ends.

[0129] Figure 11 is a flowchart showing an example of the write operation using the set value WOS target of the embodiment.

[0130] At the start of the write operation (S201), the controller 30 obtains a positioning error (S202) when the head 22 passes through the servo area SV. The controller 30 performs positioning control to position the head 22 on the target data track DTRK based on servo data. In the positioning control, by using linear interpolation of a plurality of RRO correction values obtained from the measurement of the RRO in a plurality of measurement tracks MTRK, the RRO correction value of the target data track DTRK is obtained, and the RRO correction operation using the obtained RRO correction value, that is, the linear RRO correction operation, is performed. While performing the positioning control, the controller 30 obtains the deviation amount of the head 22 from the center of the track as the positioning error.

[0131] In addition, S202 to S205 constitute a loop process. The controller 30 executes this loop process every time the head 22 passes through the servo area SV.

[0132] After S202, the controller 30 determines whether the absolute value of the positioning error is larger than the set value WOS target (S203). That is, the controller 30 determines whether the position of the head 22 has deviated from the allowable write range.

[0133] When the absolute value of the positioning error is not larger than the set value WOS target (S203: No), it can be presumed that the position of the head 22 has not deviated from the allowable write range. In this case, the controller 30 writes data to the data area DA following the just-passed servo area SV (S204). And the controller 30 determines whether all the data to be written has been written to the target data track DTRK (S205).

[0134] When all the data to be written has been written to the target data track DTRK (S205: Yes), the write operation ends. When all the data to be written has not been written to the target data track DTRK (S205: No), the control transfers to S202.

[0135] When the absolute value of the positioning error is larger than the set value WOS target (S203: Yes), it can be presumed that the position of the head 22 has deviated from the allowable write range. Therefore, the controller 30 inhibits the execution of writing and waits for the disk 11 to rotate one week (S206). When the disk 11 rotates one week, the control transfers to S202, and the process from S202 is executed again.

[0136] In this way, when the position of the head 22 deviates from the allowable write range, the write operation is interrupted, and when the head 22 approaches the interruption position of the write operation again, the process from S202 is restarted.

[0137] In addition, according to Figure 11 the example shown, when the absolute value of the positioning error is equal to the set value WOS target the control transfers to S204 and the writing of data is executed. The processing when the absolute value of the positioning error is equal to the set value WOS target is not limited to this. When the absolute value of the positioning error is equal to the set value WOS target the control may also transfer to S206.

[0138] The dWOS table 52 is generated in the manufacturing process. In the manufacturing process, the controller 30 of the disk device 1 may also generate the dWOS table 52 based on dedicated firmware. Alternatively, in the manufacturing process, the disk device 1 may be connected to a test device, and the test device may control the disk device 1 to generate the dWOS table 52.

[0139] Figure 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.

[0140] First, the controller 30 obtains the distribution in the radial direction of the positioning accuracy (S301). The controller 30 obtains the distribution of the positioning accuracy in the radial direction as shown, for example, Figure 4 by measuring the positioning accuracy at each of a plurality of positions in the radial direction. In the Figure 12 description, the positioning accuracy is, for example, the standard deviation of the position error signal for one revolution of the disk. In addition, as long as it is an evaluation index corresponding to the positioning accuracy, the controller 30 can obtain any evaluation index as the positioning accuracy.

[0141] Next, the controller 30 averages the distribution of the positioning accuracy for each of the plurality of intervals divided by the measurement tracks MTRK (S302). For example, the controller 30 divides the distribution of the positioning accuracy in the radial direction in each measurement track MTRK, such as the distribution in the interval from measurement track MTRK#0 to measurement track MTRK#1 and the distribution in the interval from measurement track MTRK#1 to measurement track MTRK#2, to obtain the distribution in a plurality of intervals. And the controller 30 obtains the average of the distribution in the interval divided by two adjacent measurement tracks MTRK by averaging the distribution in the plurality of intervals.

[0142] Next, the controller 30 generates the dWOS table 52 based on the averaged distribution of the positioning accuracy in the interval divided by two adjacent measurement tracks MTRK (S303).

[0143] For example, when the controller 30 determines the change amount dWOS for the allowable write range change determination distance d in such a manner that it can guarantee the data of adjacent data tracks regardless of the allowable write range change determination distance d, a dWOS table 52 showing the specified Figure 7 corresponding relationship is generated.

[0144] Alternatively, for example, when the controller 30 determines the change amount dWOS for the allowable write range change determination distance d in such a manner that it can guarantee the write performance regardless of the allowable write range change determination distance d, a dWOS table 52 showing the specified Figure 8 corresponding relationship is generated.

[0145] The dWOS table 52 generated through S303 is stored in a predetermined storage area. And, the work of generating the dWOS table 52 is completed.

[0146] In addition, the dWOS table 52 generated in one disk device 1 can also be used in one or more other disk devices 1. Alternatively, each disk device 1 can also individually generate the dWOS table 52. Additionally, the dWOS table 52 can also be generated by head and zone.

[0147] As described above, according to the embodiment, during the write operation, the controller 30 obtains the RRO correction value of the target data track DTRK by using interpolation of the RRO correction values of the respective measurement tracks MTRK. And, when the head 22 is positioned on the target data track DTRK, the controller 30 performs the RRO correction using the obtained RRO correction value. During the write operation, the controller 30 sets the setting value WOS based on the allowable write 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 multiple measurement tracks MTRK target . The controller 30 performs the write to the target data track DTRK when the positioning error is smaller than the setting value WOS target . The controller 30 suppresses the write to the target data track DTRK when the positioning error is larger than the setting value WOS target .

[0148] Therefore, it is possible to suppress the capacity of the non-volatile storage area required for storing information related to WOS. That is, it is possible to appropriately set WOS.

[0149] In addition, according to Figure 7 the dWOS table 52 shown, it can be considered that the change amount dWOS of the second value is associated with the allowable write 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 allowable write range change determination distance d of the third value whose absolute value is larger than the absolute value of the first value.

[0150] By using the dWOS table 52, it is possible to guarantee data on adjacent data tracks regardless of the write range change determination distance d.

[0151] In addition, when setting the WOS using the Figure 7 shown dWOS table 52, the WOS setting unit 32 can set the fifth value as the set value WOS when the write range change determination distance d is the first value target , and can set the sixth value smaller than the fifth value as the set value WOS when the write range change determination distance d is the third value whose absolute value is larger than the absolute value of the first value target .

[0152] Therefore, it is possible to guarantee data on adjacent data tracks regardless of the write range change determination distance d.

[0153] In addition, according to the Figure 8 shown dWOS table 52, it can be considered that the change amount dWOS of the seventh value is associated with the write range change determination distance d of the first value, and the change amount dWOS of the eighth value larger than the seventh value is associated with the write range change determination distance d of the third value whose absolute value is larger than the absolute value of the first value.

[0154] By using the dWOS table 52, it is possible to guarantee write performance regardless of the write range change determination distance d.

[0155] In addition, when setting the WOS using the Figure 8 shown dWOS table 52, the WOS setting unit 32 can set the ninth value as the set value WOS when the write range change determination distance d is the first value target , and can set the tenth value larger than the ninth value as the set value WOS when the write range change determination distance d is the third value whose absolute value is larger than the absolute value of the first value target .

[0156] Therefore, it is possible to guarantee write performance regardless of the write range change determination distance d.

[0157] In addition, as described above, the controller 30 evaluates the positioning error at an arbitrary radius position, and generates the dWOS table 52 based on the positioning accuracy measured in a plurality of intervals divided by a plurality of RRO measurement positions. Figure 12 By using the dWOS table 52 generated in this way, the controller 30 can appropriately set the WOS.

[0158] The controller 30 can appropriately set the WOS by using the dWOS table 52 generated in this way.

[0159] The above describes several embodiments of the present invention, but these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other ways, and various omissions, substitutions, and changes can be made without departing from the gist of the invention. These embodiments and / or their modifications are included in the scope and / or gist of the invention, and are included in the invention described in the claims and its equivalent scope.

Claims

1. A magnetic disk device comprising: magnetic head; a magnetic disk having a plurality of data tracks; and Controller, the controller, In a writing operation for one of the plurality of data tracks using the magnetic head, The second RRO correction value as the RRO correction value at the second position is obtained by interpolating a plurality of first RRO correction values ​​obtained by measuring a repeatable runout (RRO) at each of a plurality of first positions, wherein the plurality of first positions are a plurality of radial positions in a radial direction of the magnetic disk, and the second position is a position of a first data track as the one data track. When positioning the magnetic head on the first data track, performing RRO correction using the second RRO correction value, The write permission threshold is set based on a write permission range change determination distance, wherein the write permission range change determination distance is a distance between a 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-permitted threshold, writing is performed on the first data track; When the positioning error of the first data track is larger than the write permission threshold, writing to the first data track is suppressed.

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

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

4. The magnetic disk device according to claim 1, The invention further comprises a storage device for storing a reference value of the write permission threshold value and first information defining a correspondence relationship between a plurality of values ​​of the write permission range change determination distance and a plurality of values ​​of the change amount of the write permission threshold value, The controller acquires a change amount of the write permission threshold corresponding to the write permission range change determination distance based on the first information, and acquires the write permission threshold based on a reference value of the write permission threshold and the acquired change amount of the write permission threshold.

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

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

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

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