Magnetic disk device

Abstract

To provide a magnetic disk device capable of efficiently protecting data of a track adjacent to a target track of a write operation.SOLUTION: A controller of a magnetic disk device executes an accumulation operation to calculate an accumulated offset amount each time a magnetic head passes through a servo sector during a write operation in a first section. The first section is a write target section of the first track among a plurality of tracks. The accumulation operation includes adding up the positioning error amounts for two or more servo sectors, including a servo sector through which the magnetic head has passed at least last among all servo sectors through which the magnetic head has passed during the write operation. The controller executes a first protection operation for protecting data of the second track adjacent to the first track among the plurality of tracks based on the accumulated offset amount.SELECTED DRAWING: Figure 7

Description

[Technical Field]

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

[0002] Conventionally, in magnetic disk drives, when a write operation is performed, a write permission range is set along the track to which data is to be written (referred to as the target track). If the position of the magnetic head deviates from the write permission range, the magnetic disk drive stops the write operation. This protects data on tracks adjacent to the target track from being destroyed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 7,154,690 [Patent Document 2] US Patent Application Publication No. 2014 / 0168806 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of one embodiment is to provide a magnetic disk drive that can efficiently protect data on tracks adjacent to a target track of a write operation. [Means for solving the problem]

[0005] According to one embodiment, the magnetic disk drive includes a magnetic disk, a magnetic head, and a controller. The magnetic disk has a plurality of concentric tracks, with a plurality of servo sectors spaced apart on the tracks. The magnetic head writes to and reads from the plurality of tracks. During a write operation for a first section, the controller executes an accumulating operation to calculate an accumulated offset amount each time the magnetic head passes a servo sector. The write operation is executed when the positioning error amount in the servo sector last passed by the magnetic head is within a first positioning error threshold range. The first section is a write target section of a first track among the plurality of tracks. The accumulating operation includes adding up the positioning error amounts in two or more servo sectors, including at least the servo sector last passed by the magnetic head, among all servo sectors passed by the magnetic head during the write operation. The controller executes a first protection operation to protect data in a second track adjacent to the first track among the plurality of tracks based on the accumulated offset amount. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a schematic diagram showing an example of the configuration of a magnetic disk device according to the first embodiment. [Figure 2] FIG. 2 is a schematic diagram showing an example of the configuration of a magnetic disk according to the first embodiment. [Figure 3] FIG. 3 is a diagram for explaining an example of a method for setting the track pitch for the magnetic disk device of the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining an example of offset writing. [Figure 5] FIG. 5 is a diagram for explaining the timing for starting calculation of the integrated offset amount according to the first embodiment. [Figure 6] FIG. 6 is a diagram for explaining the timing of starting the protection operation according to the first embodiment. [Figure 7]FIG. 7 is a flowchart showing the procedure of the write operation of the magnetic disk device according to the first embodiment. [Figure 8] FIG. 8 is a diagram for explaining a specific example of a method for calculating an integrated offset amount according to the second modification. [Figure 9] FIG. 9 is a flowchart showing the procedure of the write operation of the magnetic disk device according to the fourth modification. [Figure 10] FIG. 10 is a flowchart showing the procedure of the write operation of the magnetic disk device according to the fifth modification. [Figure 11] FIG. 11 is a diagram for explaining a protection operation according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] The magnetic disk drive according to the embodiment will be described in detail below with reference to the accompanying drawings, but the present invention is not limited to these embodiments.

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

[0009] The magnetic disk device 1 is connected to a host 2. The magnetic disk device 1 can receive access commands such as write commands and read commands from the host 2.

[0010] The magnetic disk device 1 includes a magnetic disk 11 having a recording surface formed on its surface. The magnetic disk device 1 writes and reads data to and from the magnetic disk 11 (more precisely, the recording surface of the magnetic disk 11) in response to an access command. Although the magnetic disk device 1 may include multiple magnetic disks 11, in this embodiment, for the sake of simplicity of explanation and illustration, the magnetic disk device 1 is shown to include one magnetic disk 11.

[0011] Data is written and read via a magnetic head 22. Specifically, in addition to a magnetic disk 11, the magnetic disk device 1 includes a spindle motor 12, a motor driver IC (Integrated Circuit) 21, a magnetic head 22, an actuator arm 15, a voice coil motor (VCM) 16, a ramp 13, a head IC 24, a read / write channel (RWC) 25, RAM 27, a FROM (Flash Read Only Memory) 28, a buffer memory 29, a hard disk controller (HDC) 23, and a processor 26.

[0012] The magnetic disk 11 is rotated at a predetermined rotation speed by a spindle motor 12 attached to the rotation shaft of the magnetic disk 11. The spindle motor 12 is driven by a motor driver IC 21.

[0013] The motor driver IC 21 controls the rotation of the spindle motor 12 and the rotation of the VCM 16 .

[0014] The magnetic head 22 uses a write element 22w and a read element 22r provided therein to write and read data to and from the magnetic disk 11. The magnetic head 22 is attached to the tip of an actuator arm 15. The magnetic head 22 is moved in the radial direction of the magnetic disk 11 by a VCM 16 driven by a motor driver IC 21.

[0015] When the magnetic disk 11 is stopped from rotating, the magnetic head 22 is moved onto the ramp 13. The ramp 13 is configured to hold the magnetic head 22 at a position spaced apart from the magnetic disk 11.

[0016] During reading, the head IC 24 amplifies and outputs the signal read from the magnetic disk 11 by the magnetic head 22 and supplies it to the RWC 25. The head IC 24 also amplifies the signal corresponding to the data to be written that is supplied from the RWC 25 and supplies it to the magnetic head 22.

[0017] The HDC 23 controls the transmission and reception of data to and from the host 2 via the I / F bus, controls the buffer memory 29, and performs error correction processing on the read data.

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

[0019] The buffer memory 29 is configured, for example, by a volatile memory capable of high-speed operation. The type of memory that configures the buffer memory 29 is not limited to a specific type. The buffer memory 29 can be configured, for example, by a dynamic random access memory (DRAM), a static random access memory (SRAM), or a combination of these.

[0020] The RWC 25 modulates the data to be written that is supplied from the HDC 23 and supplies it to the head IC 24. The RWC 25 also demodulates the signal that is read from the magnetic disk 11 and supplied from the head IC 24 and outputs it to the HDC 23 as digital data.

[0021] The processor 26 is, for example, a CPU (Central Processing Unit). A RAM 27, a FROM (Flash Read Only Memory) 28, and a buffer memory 29 are connected to the processor 26.

[0022] The FROM 28 is a non-volatile memory. Firmware (program data), various operating parameters, etc. are stored in the FROM 28. The firmware may be stored on the magnetic disk 11.

[0023] The RAM 27 is configured by, for example, DRAM, SRAM, or a combination of these. The RAM 27 is used as an operating memory by the processor 26. The RAM 27 is used as an area into which firmware is loaded and an area in which various management data is held.

[0024] The processor 26 performs overall control of the magnetic disk device 1 in accordance with firmware stored in the FROM 28 or the magnetic disk 11. For example, the processor 26 loads firmware from the FROM 28 or the magnetic disk 11 into the RAM 27, and controls the motor driver IC 21, head IC 24, RWC 25, HDC 23, etc. in accordance with the loaded firmware.

[0025] The configuration including the RWC 25, the processor 26, and the HDC 23 can also be considered as the controller 30. The controller 30 may be configured as a System-On-a-Chip (SoC). The controller 30 does not necessarily have to be configured as a SoC. In addition to these, the controller 30 may also include other elements (for example, a RAM 27, a ROM 28, a buffer memory 29, or the RWC 25).

[0026] 2 is a schematic diagram showing an example of the configuration of the magnetic disk 11 according to the first embodiment. This diagram shows an example of the rotation direction of the magnetic disk 11. The magnetic head 22 moves relative to the magnetic disk 11 as the magnetic disk 11 rotates. Therefore, the write / read direction, i.e., the direction in which data is written or read by the magnetic head 22 along the circumferential direction, is opposite to the rotation direction of the magnetic disk 11.

[0027] During the manufacturing process, servo information is written to the magnetic disk 11 by, for example, a servo writer or by self-servo writing (SSW). Fig. 2 shows radially arranged servo areas 42 as an example of the arrangement of servo areas in which servo information is written. Data areas 43 in which data can be written are provided between the servo areas 42.

[0028] A plurality of concentric tracks Trk are set in the radial direction of the magnetic disk 11. A plurality of data areas 43 are provided along the tracks Trk, and a plurality of data sectors in which data is written are arranged.

[0029] An area of ​​a track Trk that is partitioned by the servo areas 42 is referred to as a servo sector. In other words, it can be thought of as a plurality of servo sectors arranged at intervals on each track Trk.

[0030] When accessing the magnetic disk 11, the magnetic head 22 reads servo information from a servo sector, and the RWC 25 estimates, based on the read servo information, the current circumferential and radial positions of the magnetic head 22. The controller 30 controls the positioning of the magnetic head 22 based on the estimated circumferential and radial positions of the magnetic head 22.

[0031] For example, the controller 30 obtains a positional error amount as an estimate of the radial position of the magnetic head 22 (referred to as an estimated radial position). The positioning error amount indicates the amount of deviation from the target track. The controller 30 controls the radial position of the magnetic head 22 so that the positioning error amount approaches zero, thereby maintaining the magnetic head 22 on the target track.

[0032] During a write operation, the controller 30 sets a write permission range having a width in the radial direction that includes the track center of the target track, and determines whether the estimated radial position of the magnetic head 22 is within the write permission range. More specifically, the controller 30 determines whether the magnetic head 22 is within the write permission range based on a comparison between the positioning error amount and a threshold value corresponding to the boundary of the write permission range. If the magnetic head 22 is not within the write permission range, the controller 30 suspends the write operation. Thereafter, when the magnetic disk 11 rotates once and the magnetic head 22 again approaches the position where the write operation was suspended, the controller 30 resumes the write operation. Such a write operation executed after suspension of the write operation is referred to as a retry write operation.

[0033] The threshold value corresponding to the write permission range is called the write off track slice WOS. In the following description, it is assumed that a positive real number is set as the write off track slice WOS, and the write permission range is the range from -WOS to +WOS with the track center of the target track as the reference.

[0034] The servo information used to estimate the radial position of the magnetic head 22 can only be obtained from multiple servo sectors spaced apart in the circumferential direction. Therefore, if the magnetic head 22 is located between servo sectors, the controller 30 cannot obtain an estimated radial position. Therefore, even if it is confirmed based on the servo information that the position of the magnetic head 22 does not deviate from the write allowable range, the position of the magnetic head 22 may deviate from the write allowable range due to disturbances or the like between the servo sectors. Such deviation of the position of the magnetic head 22 from the write allowable range is called an overrun.

[0035] The track pitch, i.e., the distance between the track centers of two adjacent tracks, is set with overrun taken into consideration. The smaller the track pitch, the greater the storage capacity of the magnetic disk drive. However, if the track pitch is too small, overrun may destroy user data on tracks adjacent to the target track (hereinafter simply referred to as adjacent tracks).

[0036] Therefore, designers set the track pitch as small as possible while minimizing the possibility of user data on adjacent tracks being destroyed by overruns. Designers estimate the distance of the overrun and set the track pitch so that it includes a margin corresponding to the estimated distance of the overrun.

[0037] 3 is a diagram for explaining an example of a method for setting the track pitch for the magnetic disk device 1 of the first embodiment. This diagram shows three tracks Trk#(N-1), Trk#N, and Trk#(N+1) that are provided consecutively in the radial direction.

[0038] 3 and the following description, the track numbers increase from the outer periphery toward the inner periphery. The positioning error amount is assumed to be numerical information that is positive on the inner periphery side of the target track and negative on the outer periphery side of the target track. The settings related to the counting method of the track numbers and the settings related to the sign of the positioning error amount are not limited to these examples.

[0039] In the example shown in FIG. 3, after a write operation is performed on track Trk#N, write operations are performed on tracks Trk#(N-1) and Trk#(N+1). PE#(N-1) is the trajectory of the positioning error amount when a write operation is performed on track Trk#(N-1). That is, PE#(N-1) indicates the position where the data on track Trk#(N-1) is written. PE#(N+1) is the trajectory of the positioning error amount when a write operation is performed on track Trk#(N+1). That is, PE#(N+1) indicates the position where the data on track Trk#(N+1) is written.

[0040] RE denotes the shape of the write element 22w. In this example, the radial width of the write element 22w is set to approximately the same as the width of each track Trk.

[0041] 3, during each write operation for track Trk#(N-1) and track Trk#(N+1), the position of the write element 22w sometimes shifts toward track Trk#N. Part of the area where the data of track Trk#N is written is then overwritten with data from track Trk#(N-1) or track Trk#(N+1), causing the width of the area where the data of track Trk#N is written to be squeezed. The dotted area indicates the area where the data of track Trk#N is written that is lost due to the squeeze.

[0042] The width of the track Trk#N that is lost due to the narrowing is represented as the narrowing amount SQZ.

[0043] The positioning error amount PE#(N-1) and the positioning error amount PE#(N+1) can be regarded as random variables uncorrelated with each other. Furthermore, the positioning error amount PE#(N-1) and the positioning error amount PE#(N+1) each have a standard deviation σ PE Based on these assumptions, the variance of the stenosis amount SQZ is 2σ PE2 Therefore, the standard deviation of the stenosis SQZ is σ SQZ can be expressed as the following equation (1).

number

[0044] The maximum value max(PE) of the positioning error amount PE of the magnetic head 22 during a write operation is kσ PE k is a constant that depends on the number of write operations. For example, k is 3.09 when 1000 write operations are performed.

[0045] Therefore, the maximum value max(SQZ) of the stenosis amount SQZ can be predicted by the following formula (2).

number

[0046] The designer determines the track pitch TP by using the maximum value max(SQZ) obtained by equation (2) as the track pitch margin TM. This prevents user data on adjacent tracks from being destroyed during a write operation. In other words, the user data on adjacent tracks is guaranteed during a write operation.

[0047] In contrast, as shown in the following equation (3), the maximum value max(PE) of the positioning error amount PE can also be considered as the sum of the write off-track slice WOS and the maximum excess amount OVR from the write off-track slice WOS due to overrun.

number

[0048] If it is assumed that the positioning error amount PE is a random variable with an expected value of zero, the maximum value max(SQZ) of the stenosis amount SQZ can be transformed into the following equation (4).

number

[0049] Therefore, the necessary track pitch margin TM can also be expressed as in the following equation (5).

number

[0050] In Figure 3, OVR max is the maximum value of the excess amount OVR, that is, max(OVR). In the example shown in Figure 3, WOS+max(OVR) is 10 nm. Therefore, the track pitch margin TM is determined to be 14 nm based on equation (5).

[0051] For some reason, writing may be performed in a state where the expected value of the positioning error amount PE is greater than zero over a long section and does not exceed the write off-track slice WOS. This type of writing state is referred to as an offset write.

[0052] 4 is a diagram illustrating an example of offset writing. In the example shown in this diagram, during a write operation to track Trk#(N+1), the magnetic head 22 (more specifically, the write element 22w) continuously passes through a position offset toward track Trk#N in section SE, even though the positioning error is less than WOS. In other words, offset writing occurs in section SE.

[0053] When such an offset write occurs, the positioning error amount PE cannot be considered a random variable in the section where the offset write occurred. Therefore, the maximum value of the narrowing amount SQZ in the section where the offset write occurred can be expressed as in the following equation (6). Note that equation (6) is an estimate of the maximum narrowing amount SQZ in the case where offset write occurs in tracks Trk on both sides of a certain track Trk.

number

[0054] From equation (6), it can be seen that the maximum value of the narrowing amount SQZ is larger than the track pitch margin TM determined based on equation (5). In other words, in such a case, protection of data on adjacent tracks during a write operation cannot be guaranteed.

[0055] In the example shown in FIG. 4, an offset write occurs on track Trk#(N+1) toward track Trk#N. In section SE where the offset write occurred, the width of track Trk#N is narrowed by 6 nm due to the offset write on track Trk#(N+1). During a write operation on track Trk#(N-1), an overrun occurs toward track Trk#N at point P1, which is included in section SE. This overrun narrows the width of track Trk#N by 10 nm. Therefore, the narrowing amount SQZ of track Trk#N at point P1 is 16 nm. At point P1, the narrowing amount SQZ exceeds the track pitch margin TM of 14 nm, making it difficult to read data from track Trk#N at point P1.

[0056] That is, to allow for offset writing, the track pitch margin TM needs to be larger than the value obtained by equation 5. However, if the value of the track pitch margin TM is increased, the storage capacity of the magnetic disk device 1 decreases.

[0057] Therefore, in the first embodiment, the controller 30 detects offset write. If offset write is detected, the controller 30 executes an operation (referred to as a protection operation) to protect the data of the adjacent track. This makes it possible to protect the data of the adjacent track without increasing the track pitch margin TM.

[0058] The controller 30 uses, as an evaluation value for detecting offset write, the integrated value of two or more estimated radial positions detected since the write operation started, i.e., the amount of positioning error. Integration means adding them together. This evaluation value is referred to as the integrated offset amount.

[0059] In the first embodiment, the controller 30 uses the value IntPE1 obtained by the following equation (7) as the cumulative offset amount. That is, the controller 30 acquires the cumulative offset amount by accumulating all estimated radial positions detected during the period in which the write operation continues after the write operation starts. Note that S in equation (7) represents the sector number of the servo sector that the magnetic head 22 has passed.

number

[0060] 5 is a diagram illustrating the timing for starting calculation of the integrated offset amount according to the first embodiment. This diagram illustrates the temporal progression of the positioning error amount PE, the temporal progression of the integrated offset amount, the temporal progression of the protection operation execution / non-execution state, and the temporal progression of the state of the write gate WG. The write gate WG is a signal for controlling the timing at which the write element 22w writes to the magnetic disk 11. In the examples shown in this diagram and subsequent figures, the period when the write gate WG is "H" indicates the period during which writing to the magnetic disk 11 is performed, and the period when the write gate WG is "L" indicates the period during which writing to the magnetic disk 11 is not performed.

[0061] The circumferential section of the target track where the write destination is located is referred to as the write target section. The write target section is made up of one or more data sectors. Here, it is assumed that at least a plurality of servo sectors are included between the beginning and end of the write target section.

[0062] The controller 30 executes an operation to move the magnetic head 22 to the target track (i.e., a seek operation). The controller 30 completes the seek operation after a settling operation to determine whether the positioning error of the magnetic head 22 on the target track is within a predetermined range. Then, when the magnetic head 22 reaches the beginning of the write target section (timing t1), the write gate WG transitions from the "L" level to the "H" level, and the controller 30 starts the write operation and calculation of the integrated offset amount IntPE1.

[0063] The integrated offset amount IntPE1 is reset to 0 at the start of a write operation, and during a write operation, the controller 30 acquires an estimated radial position, i.e., a positioning error amount PE, each time the magnetic head 22 passes a servo sector. Then, each time the controller 30 acquires a positioning error amount PE, the controller 30 accumulates the acquired positioning error amount PE to update the integrated offset amount IntPE1.

[0064] The controller 30 includes a threshold value Th that is compared with the integrated offset amount. IntPE and threshold - Th IntPE These thresholds are called offset write thresholds. IntPE From Th IntPE If the cumulative offset amount is within the range of -Th IntPE From Th IntPE If the integrated offset amount is outside the range of -Th IntPE or Th IntPE If the offset write is equal to , the controller 30 may determine that an offset write has occurred or may determine that an offset write has not occurred.

[0065] 6 is a diagram for explaining the timing of starting the protection operation according to the first embodiment. This diagram shows the transition over time of the positioning error amount PE, the transition over time of the integrated offset amount, and the transition over time of the execution / non-execution state of the protection operation.

[0066] In the example shown in FIG. 6, the integrated offset amount IntPE1 is equal to the offset write threshold value −Th during the write operation. IntPE That is, at timing t2, the integrated offset amount IntPE1 is smaller than -Th IntPE From Th IntPE The controller 30 determines whether the integrated offset amount IntPE1 is within the range of -Th IntPE When the voltage drops below 10 V, the protective action is initiated.

[0067] In the first embodiment, in the protection operation, the controller 30 executes a retry write operation.

[0068] FIG. 7 is a flowchart showing the procedure of the write operation of the magnetic disk device 1 according to the first embodiment.

[0069] The controller 30 first executes a seek operation to move the magnetic head 22 to a track Trk having a write target section (S101), and then resets the integrated offset amount IntPE1 to 0 (S102).

[0070] When the magnetic head 22 reaches the beginning of the write target section, the controller 30 starts the write operation (S103). The controller 30 changes the write gate WG from the "L" level to the "H" level at the timing when the magnetic head 22 reaches the beginning of the write target section, thereby starting writing to the magnetic disk 11 using the magnetic head 22. The controller 30 completes the settling operation before the magnetic head 22 reaches the beginning of the write target section.

[0071] The controller 30 determines whether the magnetic head 22 has reached the end of the write target section (S104). If the magnetic head 22 has reached the end of the write target section (S104: Yes), the controller 30 ends the write operation (S105), completing the series of operations.

[0072] If the magnetic head 22 has not reached the end of the write target section (S104: No), the write operation continues. When the magnetic head 22 passes a servo sector during the write operation, the controller 30 acquires the positioning error amount PE (S106). Specifically, the magnetic head 22 reads servo information from the servo sector, and the controller 30 acquires the positioning error amount PE from the read servo information.

[0073] The controller 30 determines whether the absolute value of the positioning error amount PE is larger than the write off track slice WOS (S107). That is, the controller 30 determines whether the position of the magnetic head 22 deviates from the write permitted range.

[0074] If the absolute value of the positioning error amount PE is larger than the write off track slice WOS (S107: Yes), that is, if the position of the magnetic head 22 deviates from the write permission range, the controller 30 executes a retry write operation of S110 to S112. The retry write operation will be described later.

[0075] If the absolute value of the positioning error amount PE is not larger than the write off track slice WOS (S107: No), that is, if the position of the magnetic head 22 does not deviate from the write permission range, the controller 30 executes an accumulation operation (S108). In the first embodiment, the accumulation operation is to add the positioning error amount PE to the accumulated offset amount IntPE1 and update the accumulated offset amount IntPE1 with the value obtained by the addition.

[0076] The controller 30 determines whether the absolute value of the integrated offset amount IntPE1 is equal to the offset write threshold value Th IntPEIn other words, the controller 30 determines whether the integrated offset amount IntPE1 is greater than -Th IntPE From Th IntPE It is determined whether the value deviates from the range.

[0077] The absolute value of the integrated offset amount IntPE1 is the offset write threshold value Th IntPE If it is not greater than (S109: No), that is, if the integrated offset amount IntPE1 is -Th IntPE From Th IntPE If the value does not deviate from the range up to S104, the control proceeds to S104.

[0078] The absolute value of the integrated offset amount IntPE1 is the offset write threshold value Th IntPE If it is greater than (S109: Yes), that is, if the integrated offset amount IntPE1 is -Th IntPE From Th IntPE If the value is outside the range, the controller 30 executes a retry write operation as a protective operation.

[0079] That is, the controller 30 determines whether the absolute value of the integrated offset amount IntPE1 is equal to the offset write threshold value Th IntPE If it is determined that the difference is greater than the target track, the controller 30 suspends the write operation (S110). The controller 30 waits for the magnetic disk 11 to make one revolution while continuing the tracking operation that maintains the position of the magnetic head 22 on the target track. When the magnetic disk 11 has made one revolution and the magnetic head 22 approaches the position where the write operation was suspended (S111), the controller 30 resumes the write operation (S112). Then, control transitions to S104.

[0080] Thus, according to the first embodiment, during a write operation for the write target section, the controller 30 executes an accumulating operation to accumulate the positioning error amount each time the magnetic head 22 passes a servo sector. The controller 30 executes a protection operation based on the accumulated offset amount obtained by accumulating the positioning error amount.

[0081] Therefore, when an offset write is detected, a protection operation is performed, so that data on adjacent tracks can be protected without increasing the track pitch margin TM. In other words, data on adjacent tracks can be protected efficiently.

[0082] In the first embodiment, the interval for accumulating the positioning error amount is limited to the write target interval. Since the positioning error amount obtained in the seek operation and the settling operation is excluded from the target of the accumulation operation, it is possible to detect the offset write with high accuracy.

[0083] In the first embodiment, the controller 30 executes a protection operation when the absolute value of the integrated offset amount becomes greater than the offset write threshold value.

[0084] Therefore, it is possible to perform a protective operation when an offset write occurs.

[0085] Furthermore, in the first embodiment, in the protection operation, the controller 30 suspends the write operation, and after the magnetic disk 11 has made one rotation, resumes the write operation from the position where the write operation was suspended.

[0086] Therefore, when an offset write occurs, it is possible to protect the data on the adjacent track.

[0087] 7, in the first embodiment, the controller 30 stores the last calculated offset amount without resetting it when the write operation is interrupted. Then, when the write operation is resumed, the controller 30 resumes the accumulation operation with the stored accumulated offset amount as the initial value.

[0088] The method of calculating the integrated offset amount can be modified in various ways. Modifications 1 to 3 will be described below as modifications of the method of calculating the integrated offset amount.

[0089] (Variation 1) In the first modification, the controller 30 accumulates the positioning error amount PE for the set number (denoted as i) of servo sectors passed last during the write operation. Specifically, the controller 30 obtains the accumulated offset amount IntPE2 using the following equation (8).

number

[0090] n is the ID of the last servo sector passed.

[0091] In this way, in the accumulating operation, the controller 30 accumulates the positioning error amounts of the set number of servo sectors that were passed last among all servo sectors that were passed during the write operation.

[0092] By limiting the section to be integrated to a range close to the current position of the magnetic head 22, it is possible to improve the accuracy of offset write detection.

[0093] The controller 30 may weight the positioning error amount PE obtained from the servo sectors #n to #(ni) using a weight W. That is, the controller may obtain the integrated offset amount IntPE3 using the following equation (9):

number

[0094] W(Sn) is a weight for servo sectors #n to #(ni). For example, a larger weight is assigned to a servo sector closer to the servo sector #n last passed by the magnetic head 22. Note that the method of assigning weights is not limited to this.

[0095] In this way, in the accumulating operation, the controller 30 may perform weighted addition on the positioning error amounts of the set number of servo sectors that were passed last among all servo sectors that were passed during the write operation.

[0096] (Variation 2) According to the second modification, the controller 30 determines whether the absolute value of the positioning error amount PE is greater than or equal to the threshold value Th PE If the threshold value Th is greater than the threshold value Th, the positioning error amount PE is integrated with the integrated offset amount. PE is a value greater than or equal to 0 and less than or equal to the write-off track slice WOS. The absolute value of the positioning error amount PE is equal to or less than the threshold value Th PE If the cumulative offset amount is equal to the cumulative offset amount, the controller 30 may or may not accumulate the positioning error amount against the cumulative offset amount.

[0097] The controller 30 also calculates the integrated offset amount for each of the inner circumferential side and the outer circumferential side of the target track. The integrated offset amount on the inner circumferential side is defined as the inner integrated offset amount IntPE 4I The cumulative offset amount on the outer periphery is expressed as the outer cumulative offset amount IntPE 4O It is written as follows.

[0098] That is, the controller 30 calculates the integrated offset amount IntPE using the following equations (10) to (15). 4I ,IntPE 4O Get.

number

[0099] FIG. 8 shows the integrated offset amount IntPE according to the second modification. 4I ,IntPE 4O 10 is a diagram for explaining a specific example of a calculation method of

[0100] When the magnetic head 22 passes over the servo sector #S during a write operation, the controller 30 acquires the positioning error amount PE(S) from the servo information of the servo sector #S. In the example shown in FIG. 8, the positioning error amount PE(S) is -Th PE Therefore, the controller 30 calculates the positioning error amount PE OvTh_O(S) is assigned the absolute value of the positioning error |PE(S)|, and the positioning error PE OvTh_I (S) is assigned 0. Then, the controller 30 calculates the inner integrated offset amount IntPE based on these positioning error amounts and equations (10) and (11). 4I and outer integrated offset amount IntPE 4O Calculate.

[0101] When the magnetic head 22 passes the servo sector #(S+1) during a write operation, the controller 30 obtains the positioning error amount PE(S+1) from the servo information of the servo sector #(S+1). In the example shown in FIG. 8, the positioning error amount PE(S+1) is -Th PE Therefore, the controller 30 calculates the positioning error amount PE OvTh_O (S+1) is substituted with |PE(S+1)|, and the positioning error amount PE OvTh_I Then, the controller 30 substitutes 0 for (S+1). Then, the controller 30 calculates the inner integrated offset amount IntPE based on these positioning error amounts and equations (10) and (11). 4I and outer integrated offset amount IntPE 4O Calculate.

[0102] When the magnetic head 22 passes the servo sector #(S+2) during a write operation, the controller 30 obtains the positioning error amount PE(S+2) from the servo information of the servo sector #(S+2). In the example shown in FIG. 8, the positioning error amount PE(S+2) is -Th PE From Th PE Therefore, the controller 30 calculates the positioning error amount PE OvTh_O Substitute 0 for (S+2) and calculate the positioning error amount PE OvTh_I Then, the controller 30 substitutes 0 for (S+2). Then, the controller 30 calculates the inner integrated offset amount IntPE based on these positioning error amounts and equations (10) and (11). 4I and outer integrated offset amount IntPE 4O Calculate.

[0103] When the magnetic head 22 passes the servo sector #(S+3) during a write operation, the controller 30 obtains the positioning error amount PE(S+3) from the servo information of the servo sector #(S+3). In the example shown in FIG. 8, the positioning error amount PE(S+3) is Th PE Therefore, the controller 30 calculates the positioning error amount PE OvTh_O Substitute 0 for (S+3) and calculate the positioning error amount PE OvTh_I Then, the controller 30 calculates the inner integrated offset amount IntPE based on these positioning error amounts and equations (10) and (11). 4I and outer integrated offset amount IntPE 4O Calculate.

[0104] Even if the positioning error amount PE is sufficiently close to 0, that is, the effect on adjacent tracks is sufficiently small, when that positioning error amount PE is added to the positioning error amount PE at other positions, the absolute value of the accumulated offset amount may become larger than the offset write threshold value, and it may be determined that an offset write has occurred.

[0105] According to the second modification, the controller 30 determines whether the absolute value of the positioning error amount PE of all servo sectors that the magnetic head 22 has passed through during the write operation is equal to or exceeds a threshold value Th PE If the positioning error amount PE is sufficiently close to 0, the controller 30 refrains from adding up the positioning error amount PE, thereby making it possible to improve the accuracy of offset write detection.

[0106] Furthermore, according to the second modification, the controller 30 calculates the integrated offset amount for each of the inner circumference side and the outer circumference side of the target track. The controller 30 does not necessarily have to calculate the integrated offset amount separately for the inner circumference side and the outer circumference side of the target track. In other words, the controller 30 calculates the integrated offset amount when the absolute value of the positioning error amount PE is equal to or smaller than the threshold value Th PEWhen the absolute value of the positioning error amount PE exceeds the threshold value Th, the positioning error amount PE is integrated for one integrated offset amount. PE If the sum of the positioning error amounts PE is less than the sum of the positioning error amounts PE, the sum of the positioning error amounts PE may not be calculated for the one cumulative offset amount.

[0107] However, by calculating the cumulative offset amount for each of the inner and outer circumferential sides of the target track, the following merits can be obtained.

[0108] There may be cases where the transition of the positioning error amount PE oscillates around the track center, and an offset write actually occurs. If the cumulative offset amount is calculated without distinguishing between the inner and outer sides of the target track, the offset write in the above case may not be detected, or the detection of the offset write may be delayed. By using different cumulative offset amounts for the inner and outer sides of the target track, it becomes possible to quickly detect the offset write in the above case.

[0109] (Variation 3) In the third modification, the inner integrated offset amount IntPE according to the second modification is 4I and outer integrated offset amount IntPE 4O is normalized using the number of servo sectors that the magnetic head 22 has passed. That is, the controller 30 calculates the inner integrated offset amount IntPE using the following equations (16) to (21). 5I and outer integrated offset amount IntPE 5O Calculate N sI is the amount of positioning error acquired during the period from the start of the write operation to the completion of the write operation, and is the threshold value Th PE The larger the number of servo sectors, the larger the N sO is the amount of positioning error that is included in the period from the start of the write operation to the completion of the write operation, and is the threshold value -Th PE The smaller the number of servo sectors.

number

[0110] In this way, in the accumulating operation, the controller 30 calculates the absolute value of the positioning error amounts of all servo sectors through which the magnetic head 22 has passed during the write operation, based on the threshold value Th PE The positioning error amount PE is accumulated, and the absolute value of the positioning error amount PE is calculated as the threshold value Th. PE Divide by the larger number of servo sectors.

[0111] Therefore, it is possible to prevent excessive offset continuation determination.

[0112] The protection operation can be modified in various ways. Modifications 4 and 5 of the protection operation will be described below.

[0113] (Variation 4) In the fourth modification, the off-track slice WOS is tightened as a protection operation. The off-track slice WOS is tightened to reduce the off-track slice WOS. This narrows the write permission range.

[0114] FIG. 9 is a flowchart showing the procedure of the write operation of the magnetic disk device 1 according to the fourth modification.

[0115] As in the first embodiment, the controller 30 executes the processes of S101 to S107. If it is determined in the determination process of S107 that the absolute value of the positioning error amount PE is greater than the write off track slice WOS (S107: Yes), the controller 30 executes a retry write operation (S201). The retry write operation is, for example, the processes of S110 to S112 shown in FIG.

[0116] If it is determined that the absolute value of the positioning error amount PE is not larger than the write off track slice WOS (S107: No), the controller 30 executes an accumulation operation (S108) in the same manner as in the first embodiment.

[0117] The controller 30 determines whether the absolute value of the integrated offset amount IntPE1 is equal to the offset write threshold value Th IntPE It is determined whether it is greater than the value (S109).

[0118] The absolute value of the integrated offset amount IntPE1 is the offset write threshold value Th IntPE If it is not greater than (S109: No), that is, if the integrated offset amount IntPE1 is -Th IntPE From Th IntPE If the value does not deviate from the range up to S104, the control proceeds to S104.

[0119] The absolute value of the integrated offset amount IntPE1 is the offset write threshold value Th IntPE If it is greater than (S109: Yes), that is, if the integrated offset amount IntPE1 is -Th IntPE From Th IntPE If it deviates from the range up to 10 ...

[0120] For example, the value WOS1 is used as the write-off track slice WOS up to the servo sector #S, and the absolute value of the integrated offset amount IntPE1 in the servo sector #S is the offset write threshold value Th IntPE If it is determined that it is greater than the value WOS1, the controller 30 uses a value WOS2 that is smaller than the value WOS1 as the write-off track slice WOS in servo sectors after servo sector #S+1.

[0121] After the processing of S202, the control proceeds to S104.

[0122] Thus, in a protective operation, the controller 30 may tighten the write off track slice WOS.

[0123] By tightening the write-off track slice WOS, the conditions for continuing the write operation become stricter, making it possible to protect data on adjacent tracks.

[0124] In addition, in Modification 4, the integrated offset amount IntPE1 according to the first embodiment is used as the integrated offset amount. As the integrated offset amount, the integrated offset amounts of Modifications 1 to 3 can be applied.

[0125] (Variation 5) When an off-track write occurs, it is considered that the adjacent track may be slightly difficult to read due to the off-track write. Therefore, in Modification 5, when an off-track write is detected, a protection operation is performed by rewriting the data on the adjacent track.

[0126] 10 is a flowchart showing the procedure of the write operation of the magnetic disk device 1 according to Modification 5. In the explanation of this drawing, a write operation in which a certain section of a certain track Trk#T is set as a write target section will be explained.

[0127] The controller 30 executes a seek operation to move the magnetic head 22 to the track Trk#T (S301).

[0128] Then, in steps S102 to S107, S201, and S108 to S109, the controller 30 executes the same processes as in the fourth modification.

[0129] In the determination process of S109, the absolute value of the integrated offset amount IntPE1 is equal to or greater than the offset write threshold value Th IntPE If it is determined that the value is not greater than the threshold (S109: No), the control proceeds to S104.

[0130] The absolute value of the integrated offset amount IntPE1 is the offset write threshold value Th IntPE If it is determined that the difference is greater than the threshold (S109: Yes), the controller 30 executes the protection operation according to the fifth modification.

[0131] In the protection operation, first, the controller 30 suspends the write operation (S302), and then determines whether the integrated offset amount IntPE1 is greater than 0 (S303).

[0132] If the cumulative offset amount IntPE1 is greater than 0 (S303: Yes), it is estimated that an offset write to the inner periphery has occurred. Therefore, the controller 30 rewrites data to the track Trk#(T+1) adjacent to the target track on the inner periphery.

[0133] Data rewriting is performed as follows. First, the controller 30 performs a seek operation to move the magnetic head 22 onto track Trk#(T+1) (S304). Then, the controller 30 reads data from an interval of a set length up to the circumferential position where the write operation was interrupted, and stores the read data in the buffer memory 29 (S305). Note that the storage destination is not limited to the buffer memory 29. The data can be stored in any area that can temporarily store data.

[0134] The set length is, for example, a length spanning a predetermined number of servo sectors. The designer can determine by experiment or calculation the circumferential range in which off-track writing makes reading difficult, and set the length corresponding to that range as the set length.

[0135] After the process of S305, the controller 30 writes the data stored in the buffer memory 29 to the section from which it was read (S306). That is, the data read from the section of the set length is rewritten to the section of the set length.

[0136] If the cumulative offset amount IntPE1 is not greater than 0 (S303: No), it is estimated that an offset write to the outer periphery has occurred. Therefore, the controller 30 rewrites data to track Trk#(T-1), which is adjacent to the outer periphery of the target track. That is, the controller 30 executes a seek operation to move the magnetic head 22 onto track Trk#(T+1) (S307). Then, the controller 30 executes the processes of S305 to S306.

[0137] When rewriting of the data on the adjacent track is completed, the controller 30 executes a seek operation to move the target track, i.e., the magnetic head 22, to track Trk#T (S308). Then, when the magnetic head 22 approaches the position where the write operation was interrupted (S309), the write operation is resumed (S310). Then, control transitions to S104.

[0138] In this way, the controller 30 reads data from the adjacent track and writes the read data to the adjacent track in the protection operation.

[0139] Therefore, even if it may be difficult to read data on an adjacent track due to offset writing, rewriting the data on the adjacent track makes it possible to read the data on the adjacent track. In other words, the data on the adjacent track is protected.

[0140] Furthermore, as shown in S303, the controller 30 identifies the track to be rewritten from the two tracks adjacent to the target track based on the sign of the cumulative offset amount.

[0141] Therefore, it is possible to rewrite the track affected by the offset write.

[0142] According to Modification 5, when the controller 30 detects the occurrence of an offset write, it interrupts the write operation and executes a rewrite on the adjacent track. The controller 30 may not interrupt the write operation even when it detects the occurrence of an offset write, and may execute a rewrite of the data on the adjacent track after the write operation on the write target section is completed.

[0143] Furthermore, in Modification 5, the integrated offset amount IntPE1 according to the first embodiment is used as the integrated offset amount. As the integrated offset amount, the integrated offset amounts of Modifications 1 to 3 can be applied.

[0144] (Second embodiment) As a protection operation, the first embodiment or the fourth modification of the first embodiment can be combined with the fifth modification of the first embodiment. In the second embodiment, a protection operation in which the first embodiment or the fourth modification of the first embodiment is combined with the fifth modification of the first embodiment will be described.

[0145] FIG. 11 is a diagram for explaining a protection operation according to the second embodiment.

[0146] In the second embodiment, the controller 30 executes two-stage protection operations. Two types of offset write threshold values ​​corresponding to the two-stage protection operations are set in the controller 30.

[0147] One of the two offset write thresholds is the offset write threshold ThA. IntPE and the other is the off-track write threshold ThB IntPE The offset write threshold value ThA IntPE is the offset write threshold ThB IntPE Smaller than.

[0148] For example, at timing t3, the absolute value of the integrated offset amount IntPE1 is equal to the offset write threshold value ThA IntPEThe absolute value of the integrated offset amount IntPE1 is greater than the offset write threshold value ThA IntPE In response to the fact that the voltage Vcc is greater than 1 (S401), the controller 30 executes the first stage of protective action (S402).

[0149] In the first stage of protection operation, the controller 30 executes a retry write operation (S402-1) or tightens the write off track slice WOS (S402-2).

[0150] In S402-1, the controller 30 executes a retry write operation, similar to the protection operation in the first embodiment. In the retry write operation, the controller 30 stores the cumulative offset amount IntPE1 at the time of interruption of the write operation. Then, when the write operation is resumed, the controller 30 uses the stored cumulative offset amount as the initial value of the cumulative offset amount IntPE1.

[0151] In S402-2, the controller 30 performs the contraction of the write-off-track slice WOS, similar to the protection operation of Modification 4. Here, the controller 30 initially uses a value WOS0 as the write-off-track slice WOS, and by contracting the write-off-track slice WOS, sets a value WOS1 that is smaller than the value WOS0 as the write-off-track slice WOS.

[0152] After the process of S402, at timing t4, the absolute value of the integrated offset amount IntPE1 becomes equal to the offset write threshold value ThB IntPE The absolute value of the integrated offset amount IntPE1 is greater than the offset write threshold value ThB IntPE (S403), the controller 30 executes a second-stage protection operation (S404). In the second-stage protection operation, the controller 30 executes rewriting on the adjacent track.

[0153] In this way, the absolute value of the integrated offset amount IntPE1 is equal to the offset write threshold value ThA IntPEWhen the absolute value of the integrated offset amount IntPE1 becomes larger than the offset write threshold value ThB IntPE , the controller 30 executes a rewrite to the adjacent track.

[0154] Rewriting to an adjacent track takes a relatively long time. According to the second embodiment, a protection operation different from the rewriting to the adjacent track is executed at an earlier timing than the rewriting to the adjacent track. Therefore, it is possible to reduce the frequency with which rewriting to the adjacent track is executed.

[0155] In addition, when the write-off track slice WOS is tightened in S402, the trigger for the subsequent second-stage protection operation, that is, the rewrite of the adjacent track, is the cumulative offset amount IntPE1 exceeding the offset write threshold value ThB IntPE is not limited to being greater than

[0156] For example, when the write-off-track slice WOS is contracted in S402, rewriting of the adjacent track may be performed when the absolute value of the positioning error amount becomes larger than the value WOS1. In such a case, the controller 30 may target the section in which the offset write was detected before the write-off-track slice WOS was contracted and the section in which the offset write was detected after the write-off-track slice WOS was contracted for rewriting.

[0157] In the description of the second embodiment, the integrated offset amount IntPE1 according to the first embodiment is used as the integrated offset amount. As the integrated offset amount, the integrated offset amounts according to the first to third modifications can be applied.

[0158] As described in the first embodiment, all the modifications of the first embodiment, and the second embodiment, the controller 30 performs an accumulation operation to calculate an accumulated offset amount each time the magnetic head 22 passes a servo sector during a write operation for the write target section. The accumulation operation includes adding up the positioning error amounts of two or more servo sectors, including at least the servo sector that the magnetic head 22 passed last, among all servo sectors that the magnetic head 22 passed during the write operation for the write target section. The controller 30 performs a protection operation to protect data on adjacent tracks based on the accumulated offset amount.

[0159] Therefore, it is possible to efficiently protect data on tracks adjacent to the target track.

[0160] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as defined in the claims. [Explanation of symbols]

[0161] 1 magnetic disk device, 2 host, 11 magnetic disk, 12 spindle motor, 13 ramp, 15 actuator arm, 21 motor driver IC, 22 magnetic head, 22r read element, 22w write element, 23 HDC, 24 head IC, 25 RWC, 26 processor, 27 RAM, 28 FROM, 29 buffer memory, 30 controller, 42 servo area, 43 data area, Trk track.

Claims

1. a magnetic disk having a plurality of concentric tracks, with a plurality of servo sectors spaced apart on the tracks; a magnetic head for writing to and reading from the magnetic disk; During a write operation for a first section of a first track of the plurality of tracks, which is a write target section, an accumulation operation for calculating an accumulated offset amount is performed each time the magnetic head passes a servo sector, the write operation is performed when a positioning error amount in the servo sector last passed by the magnetic head is within a first positioning error threshold range, the accumulation operation includes adding up positioning error amounts in two or more servo sectors including at least the servo sector last passed by the magnetic head out of all servo sectors passed by the magnetic head during the write operation for the first section, and a first protection operation is performed for protecting data in a second track adjacent to the first track of the plurality of tracks based on the accumulated offset amount. A controller; A magnetic disk device comprising:

2. the accumulating operation is to accumulate the positioning error amounts of all servo sectors through which the magnetic head has passed during the write operation; 2. The magnetic disk drive according to claim 1.

3. the accumulating operation is to accumulate the positioning error amounts of a predetermined number of servo sectors that the magnetic head passed last among all servo sectors that the magnetic head passed during the write operation; 2. The magnetic disk drive according to claim 1.

4. the accumulating operation is to perform weighted addition on the positioning error amounts of a predetermined number of servo sectors that the magnetic head passed last among all servo sectors that the magnetic head passed during the write operation; 2. The magnetic disk drive according to claim 1.

5. the accumulating operation is to accumulate positioning error amounts whose absolute values ​​are greater than a second positioning error threshold value among positioning error amounts of all servo sectors through which the magnetic head has passed during the write operation, the second positioning error threshold is less than or equal to the first positioning error threshold; 2. The magnetic disk drive according to claim 1.

6. The accumulating operation is to accumulate the positioning error amounts of all servo sectors through which the magnetic head has passed during the write operation, the absolute values ​​of which are greater than a second positioning error threshold, and to divide the value obtained by the accumulation by the number of servo sectors whose absolute values ​​of the positioning error amounts are greater than the second positioning error threshold.

2. The magnetic disk drive according to claim 1.

7. the controller executes the first protection operation in response to an absolute value of the integrated offset amount becoming greater than a first integrated value threshold value; 2. The magnetic disk drive according to claim 1.

8. the first protection operation is to interrupt the write operation, and then resume the write operation from the interrupted position after the magnetic disk has made one rotation.

8. The magnetic disk drive according to claim 7.

9. the controller stores the last calculated integrated offset amount when the write operation is interrupted and interrupts the integration operation, and when the write operation is resumed, resumes the integration operation with the stored integrated offset amount as an initial value.

9. The magnetic disk drive according to claim 8.

10. The controller compares the absolute value of the integrated offset amount with a first integrated value threshold value each time the magnetic head passes a servo sector, and when the absolute value of the integrated offset amount becomes larger than the first integrated value threshold value, the first protective action is to decrease the first positioning error threshold; 8. The magnetic disk drive according to claim 7.

11. the first protection operation is to read data from the second track and write the read data to the second track; 8. The magnetic disk drive according to claim 7.

12. the controller identifies the second track from two tracks adjacent to the first track based on the sign of the integrated offset amount; The magnetic disk drive according to claim 11.

13. the controller executes a second protection operation that protects data of the second track different from the first protection operation when the absolute value of the integrated offset amount becomes greater than a second integrated value threshold; the second integrated value threshold is greater than the first integrated value threshold; 13. The magnetic disk drive according to claim 11 or 12.

Images