magnetic disk drive

Abstract

To provide a magnetic disk device capable of improving write performance.SOLUTION: According to an embodiment of the present invention, a magnetic disk device includes: a magnetic disk; a magnetic head for writing data onto a track of the magnetic disk; and a controller for positioning the magnetic head and registering an address of a sector to which the data is written and a positioning error of the head at the address. The controller determines whether or not a positioning error of a second sector two tracks before the first sector to which the data is written is registered, and upon determining that the positioning error of the second sector is registered, the controller sets a first threshold value for allowing a write operation for the positioning error of the first sector based on the positioning error of the second sector. Then, the controller determines whether or not the positioning error of the first sector exceeds the first threshold value, and upon determining that the positioning error of the first sector exceeds the first threshold value, the controller stops the write operation.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] A magnetic disk device includes a magnetic disk (hereinafter also referred to as a disk), a magnetic reproducing head (hereinafter also referred to as a head) that writes data to the disk, a system controller (hereinafter also referred to as a controller), and the like. The controller controls the positioning of the head relative to multiple tracks formed on the disk in a roughly concentric pattern (hereinafter simply referred to as "positioning"). The head may be positioned off-track in the radial direction of the disk relative to the tracks. Because a large amount of off-track increases the risk of erasing data recorded on adjacent tracks, the controller sets a static threshold for the amount of off-track and stops the write operation if the amount of off-track exceeds this threshold. To quantify the risk of data erasure, the amount of track width narrowing at which the read error rate is acceptable is defined, and this is called the TPI margin. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 8,587,889 Summary of the Invention [Problem to be solved by the invention]

[0004] As the capacity of magnetic disk drives increases, the track pitch, which is the distance between adjacent tracks, decreases. This causes the TPI margin to decrease, making it easier for the off-track amount to exceed the threshold, resulting in frequent write errors and a decrease in write performance due to the overhead of retry operations. This embodiment provides a magnetic disk device that can prevent write errors and retry operations caused by the amount of off-track exceeding a threshold, thereby improving write performance. [Means for solving the problem]

[0005] A magnetic disk device according to one embodiment comprises a magnetic disk, a magnetic head that is positioned on a track of the magnetic disk having a predetermined track pitch and writes data to and reads data from the track of the disk, and a controller that positions the magnetic head and registers the address of the sector of the track to which the data is written and the positioning error of the head relative to the track at that address. The controller determines whether a positioning error of a second sector that is two tracks radially away from a first sector to which the data is written has been registered, and if a positioning error of the second sector has been registered, sets a first threshold value that allows a write operation for the positioning error of the first sector based on the positioning error of the second sector, determines whether the positioning error of the first sector exceeds the first threshold value, and stops the write operation if the positioning error of the first sector exceeds the first threshold value. [Brief explanation of the drawings]

[0006] [Figure 1] FIG. 1 is a block diagram showing the configuration of a magnetic disk device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing an example of basic write processing in a magnetic disk device. [Figure 3] FIG. 3 is a diagram showing an example of a write process of the magnetic disk device according to the embodiment. [Figure 4] FIG. 4 is a diagram showing an example of a write process of the magnetic disk device according to the embodiment. [Figure 5] FIG. 5 is a diagram showing an example of a write process of the magnetic disk device according to the embodiment. [Figure 6]FIG. 6 is a diagram showing an example of a write process of the magnetic disk device according to the embodiment. [Figure 7] FIG. 7 is a diagram showing an example of a write process of the magnetic disk device according to the embodiment. [Figure 8] FIG. 8 is a block diagram showing an example of the control configuration of the magnetic disk device according to the embodiment. [Figure 9] FIG. 9 is a block diagram showing the tightening processing circuit according to the embodiment. [Figure 10] FIG. 10 is a block diagram showing an example of the control configuration of the magnetic disk device according to the embodiment. [Figure 11] FIG. 11 is a flowchart showing the write process of the magnetic disk device according to the embodiment. [Figure 12] FIG. 12 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following FIG. [Figure 13] FIG. 13 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following FIG. [Figure 14] FIG. 14 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following FIG. [Figure 15] FIG. 15 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following FIG. 13 or 14. [Figure 16] FIG. 16 is a diagram showing an example of an off-track write table of the magnetic disk device according to the embodiment. [Figure 17] FIG. 17 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following FIG. 13 or 14. [Figure 18] FIG. 18 is a graph showing the effects of the magnetic disk device according to the above embodiment. [Figure 19] FIG. 19 is a block diagram showing a strict processing circuit of a magnetic disk device according to another embodiment. [Figure 20]FIG. 20 is a flowchart showing a write process of a magnetic disk device according to another embodiment. [Figure 21] FIG. 21 is a block diagram showing a strict processing circuit in a modified example of a magnetic disk device according to another embodiment. [Figure 22] FIG. 22 is a flowchart showing a write process in a modified example of the magnetic disk device according to the other embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments will be described with reference to the drawings. Note that the drawings are merely examples and do not limit the scope of the invention. FIG. 1 is a block diagram showing the configuration of a magnetic disk device 1 according to an embodiment. The magnetic disk device 1 includes a head disk assembly (HDA) (to be described later), a driver IC 20, a head amplifier integrated circuit (hereinafter sometimes referred to as a head amplifier IC or a preamplifier) ​​30, a volatile memory 70, a nonvolatile memory 80, a buffer memory (buffer) 90, and a system controller 130 which is a one-chip integrated circuit. The magnetic disk device 1 is also connected to a host system (host) 100.

[0008] The HDA has a magnetic disk (hereinafter referred to as the disk) 10, a spindle motor (SPM) 12, an arm 13 carrying a magnetic head 15, and a voice coil motor (VCM) 14. The disk 10 is attached to the spindle motor 12 and rotates when driven by the spindle motor 12. The arm 13 and the voice coil motor 14 form an actuator. When driven by the voice coil motor 14, the actuator controls and moves the magnetic head 15 mounted on the arm 13 to a predetermined position on the disk 10. Two or more disks 10 and magnetic heads 15 may be provided. Hereinafter, data written to each part of the magnetic disk device 1 and external devices, for example, the disk 10, may be referred to as write data, and data read from each part of the magnetic disk device 1 and external devices, for example, the disk 10, may be referred to as read data. Write data may be simply referred to as data, read data may be simply referred to as data, and write data and read data may be collectively referred to as data.

[0009] The disk 10 is allocated with the following areas where data can be written: a user data area 10a available to the user, a media cache area 10b that temporarily holds data (or commands) transferred from the host 100 or the like before writing them to a predetermined area in the user data area 10a, and a system area 10c that records information necessary for system management. Hereinafter, the direction perpendicular to the radial direction of the disk 10 will be referred to as the circumferential direction. Note that the media cache area 10b does not necessarily have to be allocated, and the system area 10c may be allocated to the non-volatile memory 80 or the like.

[0010] The magnetic head (hereinafter also referred to as the head) 15 has a slider as its main body and is equipped with a write head 15W and a read head 15R mounted on the slider. The write head 15W writes data to a track on the disk 10. The read head 15R reads data recorded on the track on the disk 10. The write head 15W may be simply referred to as the head 15, the read head 15R may be simply referred to as the head 15, or the write head 15W and the read head 15R may be collectively referred to as the head 15. The term "track" may refer to one of multiple regions obtained by dividing the disk 10 in the radial direction, one of multiple regions obtained by dividing the disk 10 in the circumferential direction, data written to a specific position on the disk 10, data written to a sector, or various other meanings. The radial width of a track is referred to as the track width, and the center position of the track width is referred to as the track center.

[0011] The driver IC 20 controls the driving of the spindle motor 12 and the VCM 14 under the control of a system controller 130 (more specifically, an MPU 60, which will be described later). The head amplifier IC (preamplifier) ​​30 includes a read amplifier and a write driver. The read amplifier amplifies a read signal read from the disk 10 by the read head 15R and outputs it to the system controller 130 (more specifically, to a read / write (R / W) channel 40, which will be described later). The write driver outputs a write current to the write head 15W according to the signal output from the R / W channel 40.

[0012] The volatile memory 70 is a semiconductor memory in which stored data is lost when the power supply is cut off. The volatile memory 70 stores data necessary for processing in each part of the magnetic disk device 1. The volatile memory 70 may be, for example, a DRAM (Dynamic Random Access Memory), or SDRAM (Synchronous Dynamic Random Access Memory). The nonvolatile memory 80 is a semiconductor memory that records stored data even when the power supply is cut off. The nonvolatile memory 80 is, for example, a NOR or NAND type flash ROM (Flash Read Only Memory: FROM). The buffer memory 90 is a semiconductor memory that temporarily stores data transmitted and received between the magnetic disk device 1 and the host 100. The buffer memory 90 may be integrated with the volatile memory 70. The buffer memory 90 may be, for example, a DRAM, an SRAM (Static Random Access Memory), an SDRAM, or an FeRAM (Ferroelectric Random Access Memory). High-speed memory (HSM), or MRAM (Magnetoresistive Random Access Memory).

[0013] The system controller (controller) 130 is realized, for example, using a large-scale integrated circuit (LSI) called a System-on-a-Chip (SoC), in which multiple elements are integrated on a single chip. The system controller 130 includes a read / write (R / W) channel 40, a hard disk controller (HDC) 50, and a microprocessor (MPU) 60. The system controller 130 is electrically connected to a driver IC 20, a head amplifier IC 30, a volatile memory 70, a nonvolatile memory 80, a buffer memory 90, and a host system 100.

[0014] The R / W channel 40 processes signals of read data transferred from the disk 10 to the host 100 and write data transferred from the host system 100 in response to instructions from the MPU 60, which will be described later. The R / W channel 40 has a circuit or function for measuring the signal quality of the read data. The R / W channel 40 is electrically connected to, for example, a head amplifier IC, the HDC 50, the MPU 60, etc.

[0015] The HDC 50 controls data transfer between the host system 100 and the R / W channel 40 in response to instructions from the MPU 60, which will be described later. The HDC 50 is electrically connected to, for example, the R / W channel 40, the MPU 60, the volatile memory 70, the nonvolatile memory 80, and the buffer memory 90.

[0016] The MPU 60 is a main controller that controls each component of the magnetic disk device 1. The MPU 60 controls the VCM 14 via the driver IC 20 and executes servo control to position the head 15. The MPU 60 also controls the SPM 12 via the driver IC 20 and rotates the disk 10. The MPU 60 controls the operation of writing data to the disk 10 and selects a destination for storing the write data. The MPU 60 also controls the operation of reading data from the disk 10 and controls the processing of the read data. The MPU 60 is connected to each component of the magnetic disk device 1. The MPU 60 is electrically connected to, for example, the driver IC 20, the R / W channel 40, and the HDC 50.

[0017] The MPU 60 includes a write control unit 610 that controls write processing, and a read control unit 620 that controls read processing. The MPU 60 executes the processing of each of these units, such as the write control unit 610 and the read control unit 620, on firmware. The MPU 60 may also include each of these units, such as the write control unit 610 and the read control unit 620, as circuits.

[0018] The write control unit 610 controls the data write process in accordance with commands from the host 100 or the like. The write control unit 610 controls the VCM 14 via the driver IC 20 to position the head 15 at a predetermined position on the disk 10 and write data. Hereinafter, "positioning the center of the head 15 (write head 15W or read head 15R) at a predetermined position" or "positioning the center of the head 15 (write head 15W or read head 15R) at a predetermined position" may also be simply referred to as "positioning the head 15 (write head 15W or read head 15R) at a predetermined position" or "positioning the head 15 (write head 15W or read head 15R) at a predetermined position." Furthermore, "positioning the head 15 (write head 15W or read head 15R) at a predetermined position" or "positioning the head 15 (write head 15W or read head 15R) at a predetermined position" may also be simply referred to as "positioning" or "positioning."

[0019] The write control unit 610 positions the head 15 (write head 15W) at a target position during write processing (hereinafter, sometimes referred to as the target position or the target write position) and writes data. The write control unit 610 positions the head 15 at the target write position and performs random writing. In other words, the write control unit 610 positions the head 15 at a target radial position during write processing (hereinafter, sometimes referred to as the target radial position or the target write radial position) at a predetermined circumferential position and writes data randomly. For example, the write control unit 610 controls the head 15 to be positioned at the target write radial position at a predetermined circumferential position and performs random writing of a predetermined sector.

[0020] The write control unit 610 controls the head 15 to be positioned at the target write position, and can randomly write data to a predetermined position (hereinafter, also referred to as the actual position or actual write position). The actual write position may be the target write position, or may be a position deviated from the target write position.

[0021] Hereinafter, "the center of the write head 15W being radially displaced from the predetermined target write position" may also be described as "the write head 15W going off-track from the predetermined track." The write control unit 610 also has a write processing circuit C1, which will be described later in the description of Fig. 8. The write processing circuit C1 may be provided outside the write control unit 610.

[0022] The read control unit 620 controls the data read process in accordance with commands from the host 100 etc. The read control unit 620 controls the VCM 14 via the driver IC 20, positions the head 15 at a predetermined position on the disk 10, and reads the data. The read control unit 620 may read the data randomly or sequentially.

[0023] The read control unit 620 positions the head 15 (read head 15R) at the target read position and reads data. The read control unit 620 positions the head 15 at the target read position and reads. In other words, the read control unit 620 controls the head 15 to be positioned at the target read radial position at a predetermined circumferential position and reads data. For example, the read control unit 620 controls the head 15 to be positioned at the target read radial position at a predetermined circumferential position and reads a predetermined sector. Note that the read control unit 620 may also control the head 15 along the target read path to read a predetermined track.

[0024] Here, the basic concept of the embodiment will be described. The head (magnetic recording / reproducing head) 15 of the magnetic disk device 1 is controlled in its radial position by an actuator including a VCM 14 so as to stay on a track formed in the circumferential direction of the magnetic disk 10. This control is also referred to as positioning control. If external vibrations or shocks are applied to the magnetic disk device 1, which is equipped with the actuator including the head and the magnetic disk 10, the head 15 may write data at an actual position that is deviated from the target position. To prevent this deviation from occurring, the magnetic disk device 1 controls the positioning of the head 15 using a feedback loop. Hereinafter, the deviation between the target position and the actual position will also be referred to as a positioning error.

[0025] If the positioning error due to positioning control is large, there is a high risk of erasing data recorded on adjacent tracks, so a threshold value (WOS: Write Offtrack Slice) is set for the positioning error, and if this threshold value is exceeded, the write operation is stopped to prevent the erasure of data recorded on adjacent tracks. This threshold value is hereinafter also referred to as the write offtrack threshold value.

[0026] The write process will be described below with reference to the drawings. 2 is a diagram showing an example of basic write processing of the magnetic disk device 1. In FIG. 2, the upper part shows an example in which data is written to three consecutive tracks arranged in the radial direction from the outer periphery in the order of track Tr0, track Tr1, and track Tr2 in the order Tr1, Tr0, and Tr2. The lower part shows an example in which the track width TW of the data area D1 of the data written on track Tr1 becomes the read limit track width TW0. In FIGS. 2 to 7, the data area of ​​the data to be protected whose track width TW becomes the read limit track width TW0 is indicated by a dashed line.

[0027] As shown in the upper part of Figure 2, each data area of ​​data written to tracks Tr0, Tr1, and Tr2 has a write width WW. The data written to track Tr0 is written shifted toward track Tr1 (hereinafter, this shifting will also be referred to as "offset"). Specifically, the data area D0 of the data written to track Tr0 is offset from the track center TC0 of track Tr0 toward the inner periphery by an error PEI (hereinafter, this will also be referred to as the positioning error, offset amount, or off-track amount). The data written on track Tr2 is written with an offset toward track Tr1. Specifically, the data area D2 of the data written on track Tr2 is positioned with an offset by an error (hereinafter also referred to as a positioning error, an offset amount, or an off-track amount) PEO from the track center TC2 of track Tr2 toward the outer periphery.

[0028] When data is written to each track as described above, the data area D1 in the data written to track Tr1 has a track width TW. The track width TW can be expressed as the following equation (1) using the write width WW, track pitch TP, error PEI, and error PEO. Here, TW represents the track width, WW represents the write width, TP represents the track pitch, and PEI and PEO represent the errors. TW = 2TP - WW - (PEO + PEI) (1) If the track width of the data area becomes smaller than the read limit track width, the data cannot be read. Specifically, if the track width TW becomes smaller than the read limit track width TW0 shown in the lower row, the data written in the data area D1 cannot be read. To prevent this, there is a limit on the total amount that can be offset from each track (track Tr0 and track Tr2) adjacent to track Tr1 when writing data. From equation (1), the sum of the error PEO and the error PEI can be expressed by the following equation. PEO+PEI=2TP-WW-TW Considering the situation where the track pitch TP is narrowed and the track width of track Tr1 is reduced to reach the read limit, the value obtained by subtracting the write width and read limit track width TW0 from twice the track pitch TP can be defined as the TPI (Track Per Inch) margin (also called track pitch squeeze margin) TM, and the condition that the sum of the errors PEO and PEI must satisfy can be expressed by the following equation (2): TW0 represents the read limit track width, and TM represents the TPI margin. PEO+PEI≦2TP-WW-TW0=TM···(2) Conventionally, limits have been set on the individual off-track amounts PEI and PEO as a sufficient condition for the sum of the errors PEI and PEO to satisfy equation (2). Specifically, the off-track amount PEO must be less than half the TPI margin TM, and the off-track amount PEI must be less than half the TPI margin TM. In other words, half the TPI margin TM was set as the threshold value for the off-track amounts PEI and PEO.

[0029] However, when the track pitch TP is reduced to increase the capacity of the magnetic disk device 1, the TPI margin TM is also reduced accordingly, as shown in equation (1), so that the off-track amounts PEO and PEI are more likely to exceed the thresholds, causing frequent write errors and a problem of reduced write performance due to the overhead caused by retry operations.

[0030] To address this issue in SMR (shingled magnetic recording) magnetic disk devices 1, a technology has been disclosed that records positioning errors during sequential writes and dynamically sets a write-off track threshold by referring to this when writing to adjacent tracks, thereby preventing a decline in write performance. However, this prior art is based on the premise that SMR performs sequential write operations, and takes advantage of the fact that the positioning error of the previous track can be stored with a small memory capacity, so this technology cannot be applied directly to random write operations.

[0031] Therefore, the embodiment of the present invention solves this problem by dynamically setting the write off-track threshold even for random writes, thereby obtaining a magnetic disk that can suppress the deterioration of write performance. Furthermore, it is also possible to obtain a magnetic disk with high track density while guaranteeing read quality.

[0032] The write processing according to this embodiment will be described below with reference to the drawings. FIG. 3 is a diagram showing an example of a write process of the magnetic disk device 1 according to the embodiment. FIG. 3 shows a case where data is written to tracks Tr1, Tr2, and Tr0 in this order. As shown in FIG. 3, data area D2 is positioned offset by an off-track amount PEO. When the off-track amount PEO of data area D2 is known, a first threshold value (also referred to as a first off-track threshold) WOS1 is determined for subsequent data writing to track Tr0. In other words, once the off-track amount PEO of data area D2 is known, the first threshold value WOS1 may be determined for writing to track Tr0. The first threshold value WOS1 is a threshold value for determining whether or not to permit a write operation when writing data to track Tr0.

[0033] The first threshold value WOS1 is a value obtained by subtracting the offset amount PEO of the data area D2 from the TPI margin TM, and can be expressed by the following equation (3): WOS1 is the first threshold value. WOS1=TM-PEO (3) The off-track amount PEI by which the data area D0 can be offset is limited by the first threshold value WOS1, and therefore the relationship between the off-track amount PEI and the first threshold value WOS1 is expressed by the following equation. PEI ≤ WOS1 = TM - PEO The above formula can be expressed using the off-track amounts PEO and PEI and the TPI margin TM as follows: PEI+PEO≦TM From the above formula, the TPI margin TM is set to a value equal to or greater than the sum of the off-track amount PEI on track Tr2 and the off-track amount PEO on track Tr0. From the above formula (PEI+PEO≦TM), formula (1) and formula (2), the following formula is established. TW≧2TP-WW-TM=TW0 That is, by setting the first threshold value WOS1 to a value obtained by subtracting the off-track amount PEO of the data area from the TPI margin TM as shown in equation (3), it is possible to ensure the track width TW for reading the data written to track Tr1. In other words, it is possible to guarantee the read quality of the data written to track Tr1.

[0034] The first threshold value WOS1 can be determined even when data is written in the order of track Tr1, track Tr0, and track Tr2. How the first threshold value WOS1 is determined when data is written in the above manner will be described with reference to FIG.

[0035] FIG. 4 is a diagram showing an example of a write process of the magnetic disk device 1 according to the embodiment. FIG. 4 shows a case where data is written to track Tr1, track Tr0, and track Tr2 in that order. As shown in FIG. 4, data area D0 is positioned offset by an off-track amount PEI. When the off-track amount PEI of data area D0 is known, a first threshold WOS1 is determined for subsequent data writing to track Tr2, as in the description of FIG. 3. In other words, once the off-track amount PEI of data area D0 is known, the first threshold WOS1 for writing to track Tr2 may be determined. The first threshold WOS1 is a threshold for determining whether or not to permit a write operation when writing data to track Tr2.

[0036] The first threshold value WOS1 is a value obtained by subtracting the offset amount PEI of the data area D0 from the TPI margin TM, and can be expressed by the following equation (4). WOS1=TM-PEI (4) By setting the first threshold WOS1 to a value obtained by subtracting the off-track amount PEI of the data area D0 from the TPI margin TM as shown in equation (4), it is possible to ensure the track width TW for reading the data written to track Tr1, as explained in Figure 3.

[0037] 5 and 6, a case where data is written in the order of track Tr1, track Tr2, and track Tr0 will be described below, but the case where data is written in the order of track Tr1, track Tr0, and track Tr2 can also be considered in the same way. In the explanation of FIG. 3, the off-track amount PEI of track Tr0 is limited by a first threshold value WOS1 determined from the offset amount PEO of the data area D2 of the data written to track Tr2 (see equation (3)). However, to prevent the offset amount PEI from being significantly limited by the first threshold value WOS1 when the offset amount PEO is extremely large and degrading the write performance of track Tr0, it may be further limited by a third threshold value WOS3 that is unrelated to the position error during writing. The third threshold value WOS3 is a static threshold value. Referring to FIG. 5, the write process when the third threshold value WOS3 is set will be explained.

[0038] 5 is a diagram showing an example of a write process of the magnetic disk device 1 according to the embodiment. As shown in FIG. 5, the off-track amount PEI of the data area D0 of the data written to the track Tr0 is limited by a predetermined third threshold value WOS3 that is unrelated to the off-track amount PEO of the data area D2 of the data previously written to the track Tr2. On the other hand, the off-track amount PEO of the data area D2 is also limited by the predetermined third threshold value WOS3.

[0039] The range in which the third threshold value WOS3 can be set will be described below. Since the off-track amount PEO is limited by the third threshold value WOS3, the relationship between the off-track amount PEO and the third threshold value WOS3 can be expressed by the following equation: WOS3 in the equation represents the third threshold value. PEO≦WOS3 Considering the equation (3) and the above equations, the relationship between the first threshold value WOS1 and the third threshold value WOS3 is expressed by the following equation. WOS1=TM-PEO≧TM-WOS3 Furthermore, taking into consideration that the first threshold WOS1 is equal to or greater than 0 and the above equation (TM-WOS3 is the lower limit of WOS1), the third threshold WOS3 can be expressed by the following equation. WOS3≦TM From the above formula, the TPI margin TM can be set as the upper limit of the third threshold WOS3.

[0040] On the other hand, the third threshold WOS3 is equal to or greater than the first threshold WOS1. Furthermore, the third threshold WOS3 is equal to or greater than the off-track amount PEO. That is, the relationship between the third threshold WOS3, the first threshold WOS1, and the off-track amount PEO can be expressed by the following equation. WOS1+PEO≦2WOS3 Considering equation (3) and the above equation, the third threshold WOS3 can be expressed by the following equation. TM / 2≦WOS3 From the above formula, half the value of the TPI margin TM can be set as the lower limit of the third threshold WOS3. That is, the settable range of the third threshold WOS3 is from half the value of the TPI margin TM to the TPI margin TM. The settable range of the third threshold WOS3 can be expressed by the following formula. TM / 2≦WOS3≦TM 5, the processing is described assuming that the off-track amount PEO of the data area D2 becomes extremely large. However, if the off-track amount PEO is a relatively small value, it is possible that the first threshold value WOS1 that limits the off-track amount PEI of the data area D0 exceeds the static third threshold value WOS3 (see equation (3)). In such a case, data may be written to the track Tr0 without being limited by the first threshold value WOS1. The write processing performed using the second threshold value WOS2 for determining whether or not to control using the first threshold value WOS1 will be described with reference to FIG. 6.

[0041] 6 is a diagram showing an example of a write process of the magnetic disk drive according to the embodiment. As shown in FIG. 6, the off-track amount PEO of data area D2 exceeds the second threshold value WOS2. In the above case, the off-track amount PEI of data area D0 for data written to track Tr0 is limited by the first threshold value WOS1.

[0042] The second threshold value WOS2 will be described in detail below. The margin of the TPI margin TM relative to the third threshold WOS3, which is a static threshold, is defined as the second threshold WOS2. In this case, the second threshold WOS2 can be expressed by the following equation (5). Note that WOS2 is the second threshold. WOS2=TM-WOS3 (5) Considering the formulas (3) and (5), the first threshold WOS1 is expressed by the following formula. WOS1=WOS3-(PEO-WOS2) Here, the condition for the first threshold value WOS1 not to exceed the third threshold value WOS3 is expressed as follows from equation (3): WOS1=TM-PEO≦WOS3 Considering the above equation and equation (5), the relationship between the second threshold value WOS2 and the amount of off-track PEO is expressed by the following equation. PEO≧TM-WOS3=WOS2 The off-track amount PEI may be limited by the first threshold value WOS1 only when the relationship between the second threshold value WOS2 and the off-track amount PEO satisfies the above formula. Also, as will be described later, since this is advantageous in terms of saving storage space, the value of PEO may be stored only when the above formula is satisfied. In other words, the second threshold value WOS2 may be used as a threshold value for determining whether or not to register the positioning error (off-track amount) PEO.

[0043] An example of a write process according to an embodiment that corresponds to an error PEO in the outer circumferential direction is shown using Figures 5 and 6, but it can also be applied to an error PEI in the inner circumferential direction, and Figure 7 shows a case where it corresponds to both an error PEO and an error PEI.

[0044] FIG. 7 is a diagram illustrating an example of a write process of the magnetic disk device 1 according to the embodiment. As shown in FIG. 7, five tracks are arranged radially from the outer periphery in the order of track Tr-2, track Tr-1, track Tr0, track Tr1, and track Tr2. FIG. 7 illustrates a situation in which data has been written to tracks Tr-2 and Tr2, but before data is written to track Tr0. Data is written off-track to track Tr0 so that the remaining width (track width) of the data written to tracks Tr-1 and Tr1 is equal to or greater than the read limit track width TW0. In other words, when writing to track Tr0, data protection by off-track writing targets tracks Tr-1 and Tr1, and the positioning of the write to track Tr0 is restricted so that the remaining width (track width) of the data on these tracks is equal to or greater than the read limit track width TW0.

[0045] If the positioning error PEO toward the outer periphery when writing to track Tr2 is equal to or less than the second threshold value WOS2 (see the upper part of FIG. 7), information about the positioning error PEO toward the outer periphery is not registered. Therefore, the offset amount toward the inner periphery when writing to track Tr0 is limited by the static third threshold value WOS3. If the positioning error PEO in the outer circumferential direction exceeds the second threshold value WOS2 when writing to track Tr2 (see the bottom of Figure 7), the information on the positioning error PEO in the outer circumferential direction is registered. Therefore, the offset amount in the inner circumferential direction when writing to track Tr0 is limited by the dynamic first threshold value WOS1. The first threshold value WOS1 is the value obtained by subtracting the registered positioning error PEO from the TPI margin TM.

[0046] If the positioning error PEI in the inner circumferential direction when writing to track Tr-2 is equal to or less than the second threshold value WOS2 (see the bottom part of FIG. 7), information about the positioning error PEI in the inner circumferential direction is not registered. Therefore, the offset amount in the outer circumferential direction when writing to track Tr0 is limited by the static third threshold value WOS3. If the positioning error PEI in the inner radial direction exceeds the second threshold value WOS2 when writing to track Tr-2 (see the upper part of Figure 7), information on the positioning error PEI in the outer radial direction is registered. Therefore, the offset amount from the inner radial direction to the outer radial direction when writing to track Tr0 is limited by the dynamic first threshold value WOS1. The first threshold value WOS1 is a value obtained by subtracting the registered positioning error PEI from the TPI margin TM.

[0047] Below, we will explain the control configuration for realizing the off-track slice tightening process that sets a threshold (the static third threshold WOS3 or the dynamic first threshold WOS1 that is a tightened version of this) and the write prohibition process that stops the write operation if the positioning error during writing exceeds the threshold. Fig. 8 is a block diagram showing an example of the control configuration of the magnetic disk device 1 according to the embodiment. In Fig. 8, the head number H is omitted from the target sector address (C, S), and only the cylinder number C and sector number S are shown. As shown in Fig. 8, the write processing circuit C1 of the write control unit 610 has an offtrack write table 611, a tightness processing circuit 612, operational amplifiers OP1 and OP2, an OR gate 613, a physical target transducer 614, a controller 615, and an actuator 616.

[0048] The target sector address (C, S) is converted to a physical target position R by a physical target position converter 614. The difference between the physical position Y where the magnetic head 15 is actually located and the physical target position R is the positioning error PE(C, S) at the sector address (C, S). Hereinafter, the "sector address" may also be simply referred to as a "sector." The positioning error PE(C,S) is input as negative feedback to the controller 615 and output as a control amount U to the actuator P. The actuator P receives the control amount U as an input and outputs the physical position Y of the magnetic head 15.

[0049] On the other hand, the positioning error PE(C, S) is input to operational amplifiers OP1 and OP2, where it is compared with an inner write offtrack threshold WOS1p (hereinafter simply referred to as the "threshold") in operational amplifier OP1, and with an outer write offtrack threshold WOS1m (hereinafter simply referred to as the "threshold") in operational amplifier OP2. If the positioning error PE(C, S) exceeds either the write offtrack threshold WOS1p or the write offtrack threshold WOS1m, a write inhibit flag WINH is output from the OR gate 613. When the write inhibit flag WINH is output from the OR gate 613, the system controller 130 (more specifically, the write control unit 610) stops the write operation.

[0050] Further, the off-track write table 611 is referenced from the target sector address (C,S), and the positioning error PEO(C+2,S) toward the outer periphery of the data area written in the sector (C+2,S) located two tracks inward, and the positioning error PEI(C-2,S) toward the inner periphery of the data area of ​​the data written in the sector (C-2,S) located two tracks outward, are output. Explaining the target sector address (C,S), sector (C+2,S), and sector (C-2,S) using Figure 7 as an example, if the target sector address (C,S) is a sector located on track Tr0, sector (C-2,S) is a sector located on track Tr-2, and sector (C+2,S) is a sector located on track Tr2. The positioning error PEO(C+2,S), the positioning error PEI(C-2,S), the default TPI margin TM, and the third threshold value WOS3, which is a static value, are input to the tightening processing circuit 612, which outputs the corresponding write off track threshold values ​​WOS1p and WOS1m.

[0051] 9 is a block diagram showing a striction processing circuit 612 according to the embodiment. As shown in FIG. 9, the striction processing circuit 612 includes operational amplifiers OP3 and OP4 and selectors SE1 and SE2. A terminal Q of selector SE1 receives an input indicating whether the positioning error PEO(C+2,S) is zero or not. If the positioning error PEO(C+2,S) is zero, the input to terminal W3 is output from terminal W1 ...EI(C-2,S) is non-zero, the input to terminal W2 is output from terminal W1. A terminal Q of selector SE2 receives an input indicating whether the positioning error PEI(C-2,S) is zero or not. If the positioning error PEI(C-2,S) is zero, the input to terminal W3 is output from terminal W1. If the positioning error PEI(C-2,S) is non-zero, the input to terminal W2 is output from terminal W1.

[0052] A static third threshold WOS3 is input to terminal W3. A value obtained by subtracting the positioning error PEI(C-2,S) from the TPI margin TM, or a value obtained by subtracting the positioning error PEO(C+2,S) from the TPI margin TM, is input to terminal W2. 10 is a block diagram showing an example of the control configuration of the magnetic disk device 1 according to the embodiment. Fig. 10 shows a configuration for registering and updating positioning errors in the off-track write table 611.

[0053] The positioning error PE(C,S) during writing to the target sector address (C,S) is input to an absolute value circuit 617, which outputs the absolute value PEA of the positioning error PE(C,S). The absolute value PEA is compared with a second threshold value WOS2 for registration determination in an operational amplifier OP5. If the absolute value PEA exceeds the second threshold value WOS2, the operational amplifier OP5 outputs a registration flag RF1 as 1, and if the absolute value PEA does not exceed the second threshold value WOS2, the operational amplifier OP5 outputs a registration flag RF1 as 0.

[0054] On the other hand, the off-track write table reference update block (hereinafter also referred to as the OWT reference update block) 619 outputs the past maximum positioning error PEP in the target direction of the target sector (for example, sector (C, S)). The target direction here means the same direction as the positioning error PE(C, S). The operational amplifier OP6 compares the past maximum positioning error PEP with the absolute value PEA of the current positioning error PE(C,S), and outputs the update flag RF2 as 1 if the absolute value PEA exceeds the maximum positioning error PEP, and outputs the update flag RF2 as 0 if the absolute value PEA does not exceed the maximum positioning error PEP. Note that if there is no entry for sector (C,S) in the OWT reference update block 619 (to be described later in the description of FIG. 16), the maximum positioning error PEP is output as 0, and therefore the operational amplifier OP6 outputs the update flag RF2 as 1. The operational amplifier OP7 outputs a flag DPE as 1 when the positioning error PE(C,S) is smaller than 0, and outputs a flag DPE as 0 when the positioning error PE(C,S) is not smaller than 0. In other words, the sign of the positioning error PE(C,S) can be identified by the flag DPE. When the registration flag RF1 is output as 1 and the update flag RF2 is output as 1, the AND gate 618 outputs the update registration flag RF as 1. When the update registration flag RF is output as 1, the information (more specifically, PEI(C,S) or PEO(C,S)) corresponding to the sign of the positioning error PE(C,S) is updated or newly registered in the off-track write table 611.

[0055] The write processing procedure of the present invention will now be described. First, the determination of the write inhibit flag WINH and the write offtrack thresholds WOS1p and WOS1m, which were explained in Fig. 8 and Fig. 9, will be explained using Fig. 11 and Fig. 12. Fig. 11 is a flowchart showing the write processing of the magnetic disk device according to the embodiment. Fig. 12 is a flowchart following Fig. 11, showing the write processing of the magnetic disk device according to the embodiment.

[0056] 11, when the write process starts, in step S5, the system controller 130 performs a seek operation to a target sector address (C, H, S). The seek operation is an operation of moving the head 15W to a target position (for example, the target sector address (C, H, S)). Next, in step S10, the system controller 130 sets the inner write off-track threshold WOS1p to an initial value +WOS3, and sets the outer write off-track threshold WOS1m to an initial value -WOS3.

[0057] After setting the write-off track thresholds WOS1p and WOS1m in step S10, the system controller 130 determines in step S15 whether a positioning error PEO(C+2,H,S) in the sector (C+2,H,S) two tracks inward from the target position has been registered. If it is determined in step S15 that the positioning error PEO(C+2,H,S) has not been registered, the process proceeds to step S25.

[0058] On the other hand, if it is determined that the positioning error PEO(C+2,H,S) is registered (step S15), the process proceeds to step S20, where the write off track threshold WOS1p is set to a value obtained by subtracting the positioning error PEO(C+2,H,S) from the TPI margin TM. The write off track threshold WOS1p can be expressed by the following formula: WOS1p is the write off track threshold, and PEO is the positioning error in sector (C+2,H,S). WOS1p=+(TM-PEO) In step S20, the write off track threshold WOS1p is set, and then the process proceeds to step S25.

[0059] In step S25, the system controller 130 determines whether the positioning error PEI(C-2,H,S) in the sector (C-2,H,S) two tracks outside the target position has been registered. If it is determined in step S25 that the positioning error PEI(C-2,H,S) has not been registered, the process proceeds to step S35 (see FIG. 12). On the other hand, if it is determined that the positioning error PEI(C-2,H,S) is registered (step S25), the process proceeds to step S30, where the write off-track threshold WOS1m is set to a value obtained by subtracting the positioning error PEI(C-2,H,S) from the TPI margin TM. The write off-track threshold WOS1m can be expressed by the following formula: WOS1m is the write off-track threshold, and PEI is the positioning error in sector (C-2,H,S). WOS1m=-(TM-PEI) In step S30, after the write-off-track threshold WOS1m is set, the process proceeds to step S35.

[0060] Next, in step S35, the system controller 130 determines whether the positioning error PE in the target sector (C, H, S) is greater than the write off-track threshold WOS1p. If the positioning error PE is greater than the write off-track threshold WOS1p, the system controller 130 proceeds to step S50 and prohibits the write operation.

[0061] If the positioning error PE is smaller than the write off-track threshold WOS1p (step S35), the process proceeds to step S40, where the system controller 130 determines whether the positioning error PE is smaller than the write off-track threshold WOS1m. If the positioning error PE is smaller than the write off-track threshold WOS1m, the process proceeds to step S50, where the system controller 130 prohibits the write operation. If the positioning error PE is greater than the write off-track threshold WOS1m (step S40), the process proceeds to step S45, where a write operation is performed.

[0062] It should be noted that steps S15 and S20 and steps S25 and S30 can be interchanged. Using Fig. 11 as an example, step S25 may be performed after setting the write off track thresholds WOS1p and WOS1m in step S10, and step S15 may be performed if no positioning error PEI has been registered. Similarly, steps S35 and S40 may be interchanged.

[0063] The procedure for registering positioning errors in the off-track write table 611 explained in Fig. 10 will be explained using Fig. 13. Fig. 13 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following Fig. 12. After the write operation is performed in step S45 (see FIG. 12), the process proceeds to step S55, where the system controller 130 determines whether the positioning error PE is smaller than 0, and if the positioning error PE is smaller than 0, the process proceeds to step S60.

[0064] In step S60, the system controller 130 determines whether the positioning error PEO(C,H,S) in the outer circumferential direction in sector (C,H,S) has already been registered. If the positioning error PEO(C,H,S) has not already been registered, the system controller 130 proceeds to step S70, where it registers the positioning error PEO(C,H,S) as the absolute value of the positioning error PE.

[0065] In step S60, if the positioning error PEO(C,H,S) has already been registered, the process proceeds to step S65, where the system controller 130 determines whether the absolute value of the positioning error PE is greater than the registered positioning error PEO(C,H,S), and if the absolute value of the positioning error PE is not greater than the registered positioning error PEO(C,H,S), the process proceeds to step S95 (see FIG. 15 for step S95).

[0066] If the absolute value of the positioning error PE is greater than the registered positioning error PEO(C,H,S) (step S65), the system controller 130 proceeds to step S70, where it updates the positioning error PEO(C,H,S) with the absolute value of the positioning error PE, and then proceeds to step S95.

[0067] On the other hand, if the positioning error PE is greater than 0 in step S55, the process proceeds to step S75, where the system controller 130 determines whether the positioning error PEI(C,H,S) in the inner peripheral direction in sector (C,H,S) has been registered. If the positioning error PEI(C,H,S) has not been registered, the process proceeds to step S85, where the absolute value of the positioning error PE is registered as the positioning error PEI(C,H,S).

[0068] In step S75, if the positioning error PEI(C,H,S) has already been registered, the process proceeds to step S80, where the system controller 130 determines whether the absolute value of the positioning error PE is greater than the registered positioning error PEI(C,H,S), and if the absolute value of the positioning error PE is not greater than the registered positioning error PEI(C,H,S), the process proceeds to step S95.

[0069] If the absolute value of the positioning error PE is greater than the registered positioning error PEI(C,H,S) (step S80), the system controller 130 proceeds to step S85, where it updates the positioning error PEI(C,H,S) with the absolute value of the positioning error PE, and then proceeds to step S95.

[0070] Although the registration of the positioning error in the off-track write table 611 has been described, it may be determined whether or not to register the positioning error by adding the second threshold value WOS2 described in Fig. 6. A specific example is shown in Fig. 14. FIG. 14 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following FIG.

[0071] 14, after the write operation is performed in step S45 (see FIG. 12), the process proceeds to step S90, where the system controller 130 determines whether the absolute value of the positioning error PE is greater than the second threshold value WOS2. If the absolute value of the positioning error PE is greater than the second threshold value WOS2, the process from step S55 to step S70 or from step S55 to step S85 described in FIG. If the absolute value of the positioning error PE is smaller than the second threshold value WOS2, the process proceeds to step S95.

[0072] Next, a procedure for canceling information registered in the off-track write table 611 will be described. Fig. 15 is a flowchart showing the write processing of the magnetic disk device according to the above embodiment, following Fig. 13 or 14. Fig. 15 shows the procedure for canceling information registered in the off-track write table 611.

[0073] 15, in step S95, the system controller 130 determines whether or not a positioning error PEO(C+1,H,S) toward the outer periphery of the sector (C+1,H,S) located one track inward of the sector (C,H,S) on which the write operation was performed has been registered. If the positioning error PEO(C+1,H,S) has been registered, the system controller 130 proceeds to step S105, where it clears the positioning error PEO(C+1,H,S). The term "clear" as used above means "setting the value of the positioning error PEO(C+1,H,S) to 0." Then, the system controller 130 proceeds to step S100. If the positioning error PEO(C+1, H, S) has not been registered (step S95), the process proceeds to step S100.

[0074] In step S100, the system controller 130 determines whether the positioning error PEI(C-1,H,S) in the inner peripheral direction of the sector (C-1,H,S) located one track outward from the sector (C,H,S) on which the write operation was performed has been registered. If the positioning error PEO(C-1,H,S) has been registered, the system controller 130 proceeds to step S110, where it clears the positioning error PEI(C-1,H,S). Then, the write process to the target position is terminated. In other words, the process of canceling the registration information is a process of canceling the registration of the positioning error of sectors (C+1,H,S) and (C-1,H,S) adjacent to sector (C,H,S) to sector (C,H,S) when data is written to sector (C,H,S).

[0075] Here, the entries in the off-track write table 611 will be described. FIG. 16 is a diagram showing an example of the off-track write table 611 of the magnetic disk drive according to the embodiment. Each entry contains the track's cylinder number C, head number H, sector number S, inner positioning error PEI, and outer positioning error PEO. In one example, a serial number is assigned to each entry, and 2,401 sectors are entered. Here, "entered" means "information is registered." Furthermore, in one example, the maximum number of entries (hereinafter referred to as the "number of entries") is set to 10,000, but information on all sectors may be stored in the off-track write table 611 if the storage capacity allows. If a maximum number of entries is set, information on unnecessary sectors is deregistered.

[0076] The deregistration process will be described in detail below. Specifically, the deregistration process is performed when a registered sector no longer affects adjacent tracks, and is performed on the information of the registered sector whose adjacent tracks have been overwritten. When a sector located one track inward of a registered sector is overwritten, the positioning error PEI of the registered sector is cleared. In other words, the positioning error PEI is set to 0. When a sector located one track outward of a registered sector is overwritten, the positioning error PEO of the registered sector is cleared. In other words, the positioning error PEO is set to 0. When both the positioning error PEI and the positioning error PEO of a registered sector become 0, the registration is cancelled for the information of that registered sector, thereby cancelling the entry of that registered sector.

[0077] The procedure for the above-mentioned deregistration process will be explained below. Fig. 17 is a flowchart showing the write processing of the magnetic disk device according to the embodiment, following Fig. 13 or 14. Note that steps S95, S100, S105, and S110 are the same as those described in Fig. 15, and therefore will not be described here.

[0078] 17, after clearing the positioning error PEO(C+1,H,S) in the outer circumferential direction in sector (C+1,H,S) in step S105, the process proceeds to step S115. In step S115, the system controller 130 determines whether the positioning error PEI(C+1,H,S) in the inner circumferential direction in sector (C+1,H,S) is 0, and if the positioning error PEI(C+1,H,S) is not 0, the process proceeds to step S100.

[0079] If the positioning error PEI(C+1, H, S) is 0 (step S115), the process proceeds to step S120, where the system controller 130 cancels the entry in sector (C+1, H, S). Then, the process proceeds to step S100.

[0080] In step S110, the positioning error PEI(C-1,H,S) in the inner radial direction in sector (C-1,H,S) is cleared, and then the process proceeds to step S125. In step S125, the system controller 130 determines whether the positioning error PEO(C-1,H,S) in the outer radial direction in sector (C-1,H,S) is 0, and if the positioning error PEO(C-1,H,S) is not 0, the process of writing to the target position ends.

[0081] If the positioning error PEO(C-1, H, S) is 0 (step S125), the process proceeds to step S130, where the system controller 130 cancels the entry in sector (C-1, H, S). Thereafter, the write process to the target position is completed.

[0082] Next, the effect of applying the above write processing will be described. Fig. 18 is a graph showing the effect of the magnetic disk drive according to the embodiment. In Fig. 18, the horizontal axis represents the TPI gain, which indicates the ratio to the default track density achieved by reducing the required value of the TPI margin TM and narrowing the track pitch TP. The vertical axis represents the performance index, which indicates the ratio of the number of random writes per hour under a vibration environment (specifically, a positioning error 3σ value of 6.1 nm) relative to the desktop environment. The dashed line indicates the case where the write off-track threshold is narrowed uniformly as in the conventional case, and the solid line indicates the case where the write off-track threshold is dynamically narrowed based on write positioning information for two tracks ahead.

[0083] As shown in FIG. 18, performance improvement effects are apparent up to a TPI gain of the default 1.25 times. For example, when the performance index in a vibration environment is 0.9, the TPI gain indicated by the dashed line is approximately 1.1 times, and the TPI gain indicated by the solid line is approximately 1.25 times. Therefore, by dividing 1.1 from 1.25, it can be seen that there is a potential of 1.13 times.

[0084] The magnetic disk device 1 configured as described above includes the magnetic disk 10, the magnetic head 15, and the controller 130. The controller 130 determines whether or not positioning errors PEI and PEO are registered in the sector two tracks ahead of the sector to be written, and if so, sets a first threshold value WOS1 based on the positioning errors PEI and PEO, and determines whether or not to perform a write operation based on the first threshold value WOS1 and the positioning error PE of the sector to be written. The controller 130 registers both the positioning error PEI in the inner circumferential direction and the positioning error PEO in the outer circumferential direction. The controller 130 determines whether or not to register the positioning errors PEI and PEO based on the positioning error PE of the sector to be written and a second threshold value WOS2 for determining whether or not to register them. The first threshold value WOS1 is a value obtained by subtracting the positioning errors PEI and PEO registered in the sector two tracks ahead of the sector to be written from a predetermined TPI margin. This makes it possible to maintain the track width TW at or above the read limit track width TW0 without uniformly narrowing the write off track thresholds WOS1p and WOS1m, thereby obtaining a magnetic disk device that can maintain read quality while suppressing write errors and retry operations caused by the positioning error PE exceeding the threshold, thereby improving write performance.

[0085] The controller 130 may cancel the registration of the positioning errors PEI and PEO that have been registered in sectors adjacent to the sector where data has been written, thereby making it possible to deal with the off-track write table 611 having an upper limit on the number of entries.

[0086] If no positioning errors PEI, PEO are registered in the sector two tracks ahead of the sector to be written, the controller 130 determines whether or not to perform a write operation based on the positioning error PE of the sector to be written and a fixed static third threshold value WOS3. The third threshold WOS3 has a magnitude between half the TPI margin and the TPI margin, which makes it possible to prevent the dynamic write off track thresholds WOS1p and WOS1m from being excessively relaxed.

[0087] (Other embodiments) Next, a magnetic disk device 1 according to another embodiment will be described. The magnetic disk device 1 is the same as the above embodiment except for the points described in the other embodiment. First, we will explain the write process of the magnetic disk device 1. The definition of the first threshold value is different between the above embodiment and other embodiments, but the write procedure is the same. Therefore, we will explain in detail the first threshold value WOS12 in other embodiments.

[0088] In the above embodiment, the first threshold value WOS1 shown in Fig. 3 is expressed by formula (3), and the second threshold value WOS2 shown in Fig. 6 is expressed by formula (5). The first threshold value WOS1 in the above embodiment can be expressed by the following formula from formulas (3) and (5). WOS1=WOS3-(PEO-WOS2) In another embodiment, the first threshold value WOS12 can be expressed by the following equation, which is obtained by multiplying the difference (PEO-WOS2) between the positioning error PEO and the second threshold value WOS2 shown in the above equation by a predetermined gain GAIN: WOS12 is the first threshold value in another embodiment, and GAIN is the predetermined gain. WOS12 = WOS3 - GAIN × (PEO - WOS2) Here, the first threshold value WOS12 is expressed by the following equation (6) based on the above equation and equation (5). WOS12=TM+G0-GAIN×PEO...(6) Here, G0 is a constant and a predetermined amount expressed by the following formula. G0 = (GAIN-1) × WOS2 Furthermore, when equation (3) is taken into consideration, equation (6) can be transformed into the following equation. WOS12=WOS1+(1-GAIN)×(PEO-WOS2) From the above equation, when the positioning error PEO is larger than the second threshold value WOS2 and the gain GAIN is larger than 1, the first threshold value WOS12 for the positioning error PEI to be written will be smaller than the first threshold value WOS1 in the above embodiment. Also, from the above, the gain GAIN is a value equal to or larger than 1, such as 1.5 or 2.

[0089] On the other hand, the first threshold value WOS1 in the embodiment shown in FIG. 4 can be expressed by the following equation from equations (4) and (5). WOS1=WOS3-(PEI-WOS2) In another embodiment, the first threshold value WOS12 can be expressed by the following equation obtained by multiplying the difference (PEI-WOS2) between the positioning error PEI and the second threshold value WOS2 shown in the above equation by a predetermined gain GAIN. WOS12 = WOS1 + GAIN (PEI - WOS2) Here, the first threshold value WOS12 is expressed by the following equation (7) based on the above equation and equation (5). WOS12=TM+G0-GAIN×PEI...(7) Furthermore, taking into account equation (3), equation (7) can be transformed into the following equation. WOS12=WOS1+(1-GAIN)×(PEI-WOS2) From the above equation, when the positioning error PEI is greater than the second threshold value WOS2 and the gain GAIN is greater than 1, the first threshold value WOS12 for the positioning error PEO to be written will be smaller than the first threshold value WOS1 in the above embodiment. Also, from the above, the gain GAIN is a value greater than or equal to 1, such as 1.5 or 2.

[0090] Next, a description will be given of a striction processing circuit 612 of a magnetic disk device 1 according to another embodiment. Fig. 19 is a block diagram showing the striction processing circuit 612 of the magnetic disk device 1 according to another embodiment. As shown in Fig. 19, the striction processing circuit 612 further includes gain amplifiers GA1, GA2, and GA3, an operational amplifier OP8, and an amplifier AN.

[0091] The gain amplifier GA1 outputs a value obtained by multiplying the input positioning error PEO(C+2,S) by the gain GAIN (hereinafter also referred to as the “product of the positioning error PEO(C+2,S) and the gain GAIN”) to the operational amplifier OP3 and the selector SE1. The gain amplifier GA2 outputs a value obtained by multiplying the input positioning error PEI(C-2,S) by the gain GAIN (hereinafter also referred to as the “product of the positioning error PEI(C-2,S) and the gain GAIN”) to the operational amplifier OP4 and the selector SE2. The gain amplifier GA3 outputs a value obtained by multiplying the input second threshold value WOS2 by the gain GAIN to the operational amplifier OP8. The operational amplifier OP8 outputs a value (predetermined amount G0) obtained by subtracting the second threshold value WOS2 from the value input from the gain amplifier GA3 to the amplifier AN. The amplifier AN outputs a value obtained by adding the predetermined amount G0 to the TPI margin TM to the operational amplifiers OP3 and OP4.

[0092] Terminal Q of selector SE1 receives an input indicating whether the product of positioning error PEO(C+2,S) and gain GAIN is zero. If the value input from terminal Q is zero, selector SE1 outputs the value input to terminal W1, and if the value input from terminal Q is other than zero, it outputs the value input to terminal W2. Terminal Q of selector SE2 receives an input indicating whether the product of the positioning error PEI(C-2, S) and the gain GAIN is zero or not. If the value input from terminal Q is zero, selector SE2 outputs the value input to terminal W1, and if the value input from terminal Q is other than zero, selector SE2 outputs the value input to terminal W2.

[0093] A static third threshold WOS3 is input to terminal W3. A value obtained by subtracting the value obtained by multiplying the positioning error PEO(C+2,S) by the gain GAIN from the sum of the TPI margin TM and the predetermined amount G0, or a value obtained by subtracting the value obtained by multiplying the positioning error PEI(C-2,S) by the gain GAIN from the sum of the TPI margin TM and the predetermined amount G0, is input to terminal W2.

[0094] Next, a procedure for determining the write off-track thresholds WOS1p and WOS1m of a magnetic disk device 1 according to another embodiment will be described. Fig. 20 is a flowchart showing the write processing of a magnetic disk device 1 according to another embodiment. Note that, since the processing other than steps S21 and S31 is the same as that of the above embodiment, only steps S21 and S31 will be described.

[0095] 20, if it is determined in step S15 that the positioning error PEO(C+2,H,S) is registered, the process proceeds to step S21, where the system controller 130 sets the write off track threshold WOS1p to a value obtained by adding a predetermined amount G0 to the TPI margin TM and subtracting the product of the positioning error PEO(C+2,H,S) and the gain GAIN. The write off track threshold WOS1p can be expressed by the following equation: WOS1p is the write off track threshold, and PEO is the positioning error in sector (C+2,H,S). WOS1p = + (TM + G0 - GAIN × PEO) In step S21, the write-off-track threshold WOS1p is set, and then the process proceeds to step S25.

[0096] If it is determined in step S25 that the positioning error PEI(C-2,H,S) is registered, the process proceeds to step S31, where the system controller 130 sets the write off track threshold WOS1m to a value obtained by adding a predetermined amount G0 to the TPI margin TM and subtracting the product of the positioning error PEI(C-2,H,S) and the gain GAIN. The write off track threshold WOS1m can be expressed by the following equation: WOS1m is the write off track threshold, and PEI is the positioning error in sector (C-2,H,S). WOS1m=-(TM+G0-GAIN×PEI) In step S31, a write-off-track threshold WOS1m is set, and then the process proceeds to step S35.

[0097] The effects of the magnetic disk device 1 according to the other embodiment will be described below. In the magnetic disk device 1 configured as described above, the first threshold value WOS12 is calculated by adding a predetermined amount G0 to a predetermined TPI margin TM, and subtracting the product of a predetermined gain GAIN and the positioning errors PEI and PEO registered in the sector two tracks ahead of the sector to be written. In this case, the gain GAIN is a value of 1 or more. Furthermore, the predetermined amount G0 is the product of a value obtained by subtracting 1 from the predetermined gain GAIN and a second threshold value WOS2. This makes it possible to reduce the positioning errors PEI and PEO, and therefore ensure a sufficient track width TW even when the track pitch TP is reduced (see equation (1)). For the above reasons, it is possible to obtain a magnetic disk drive 1 with improved recording density.

[0098] (Variation) A modified example of the magnetic disk device 1 according to another embodiment will now be described. The magnetic disk device 1 is the same as the other embodiments except for what will be described in this modified example. In the above embodiment, the first threshold value WOS1 shown in Fig. 3 is expressed by equation (3). In the modified example, the first threshold value WOS13 can be expressed by the following equation (8) obtained by multiplying the positioning error PEO of equation (3) by a predetermined gain GAIN. Note that WOS13 indicates the first threshold value in the modified example. WOS13 = TM-GAIN × PEO (8) Considering equation (3), equation (8) can be transformed into the following equation: WOS13=WOS1+(1-GAIN)×PEO From the above equation, if the gain GAIN is greater than 1, the first threshold value WOS12 for the positioning error PEI to be written will be smaller than the first threshold value WOS1 in the above embodiment. From the above, the gain GAIN is a value of 1 or greater.

[0099] On the other hand, in the above embodiment, the first threshold value WOS1 shown in Fig. 4 is expressed by equation (4). In the modified example, the first threshold value WOS13 can be expressed by the following equation (9) obtained by multiplying the positioning error PEI of equation (4) by a predetermined gain GAIN. WOS13 = TM-GAIN × PEI (9) Considering equation (3), equation (9) can be transformed into the following equation: WOS13=WOS1+(1-GAIN)×PEI From the above equation, if the gain GAIN is greater than 1, the first threshold value WOS13 for the positioning error PEO to be written will be smaller than the first threshold value WOS1 in the above embodiment. From the above, the gain GAIN is a value of 1 or greater.

[0100] Next, a description will be given of a strict processing circuit 612 in a modified example of the magnetic disk device 1 according to another embodiment. Fig. 21 is a block diagram showing a strict processing circuit 612 in a modified example of the magnetic disk device 1 according to another embodiment. As shown in FIG. 21, the tightening processing circuit 612 is configured without a gain amplifier GA3, an operational amplifier OP8, and an amplifier AP. A static third threshold WOS3 is input to terminal W3. A value obtained by subtracting the product of the positioning error PEO(C+2,S) and the gain GAIN from the TPI margin TM, or a value obtained by subtracting the product of the positioning error PEI(C-2,S) and the gain GAIN from the TPI margin TM, is input to terminal W2.

[0101] Next, a procedure for determining the write off-track thresholds WOS1p and WOS1m in a modified magnetic disk device 1 according to another embodiment will be described. Fig. 22 is a flowchart showing the write processing in a modified magnetic disk device 1 according to another embodiment. Note that, since the processing other than steps S22 and S32 is the same as in the other embodiments, only steps S22 and S32 will be described.

[0102] 22, if it is determined in step S15 that the positioning error PEO(C+2,H,S) is registered, the process proceeds to step S22, where the system controller 130 sets the write off track threshold WOS1p to a value obtained by subtracting the product of the positioning error PEO(C+2,H,S) and the gain GAIN from the TPI margin TM. The write off track threshold WOS1p can be expressed by the following equation: WOS1p is the write off track threshold, and PEO is the positioning error in sector (C+2,H,S). WOS1p = + (TM-GAIN × PEO) In step S22, the write off track threshold WOS1p is set, and then the process proceeds to step S25.

[0103] If it is determined in step S25 that the positioning error PEI(C-2,H,S) is registered, the process proceeds to step S32, where the system controller 130 sets the write off track threshold WOS1m to a value obtained by subtracting the product of the positioning error PEI(C-2,H,S) and the gain GAIN from the TPI margin TM. The write off track threshold WOS1m can be expressed by the following equation: WOS1m is the write off track threshold, and PEI is the positioning error in sector (C-2,H,S). WOS1m = -(TM-GAIN × PEI) In step S32, the write-off-track threshold WOS1m is set, and then the process proceeds to step S35.

[0104] In the magnetic disk device 1 configured as described above, the first threshold value WOS13 is a value obtained by subtracting the product of a predetermined gain GAIN and the positioning errors PEI and PEO registered in the sector two tracks ahead of the sector to be written from a predetermined TPI margin TM, thereby achieving the same effects as in the other embodiments.

[0105] Although the embodiments of the present invention have been described, the above embodiments are presented as examples and are not intended to limit the scope of the invention. The novel embodiments described above can be embodied in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The above 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]

[0106] 1...magnetic disk device, 10...magnetic disk, 15...magnetic head, 15W...write head, 130...system controller, 610...write control section, 611...off-track write table, 612...tightening processing circuit, 613...OR gate, 617...absolute value circuit, 618...AND gate, 619...OWT reference update block, GAIN...gain, predetermined amount...G0, PEO, PEI...positioning error, Tr-2, Tr-1, Tr0, Tr1, Tr2...track, WOS1, WOS12, WOS13...first threshold, WOS2...second threshold, WOS3...third threshold

Claims

1. A magnetic disk, a magnetic head positioned at a track having a predetermined track pitch on the magnetic disk, for writing data to the track of the magnetic disk and reading data from the track of the magnetic disk; a controller that positions the magnetic head and registers the address of the sector in which the data of the track is written and the positioning error of the magnetic head relative to the track at the address; The controller determining whether or not a positioning error of a second sector located two tracks away in a radial direction from a first sector into which the data is to be written has been registered, and if a positioning error of the second sector has been registered, setting a first threshold value for allowing a write operation for the positioning error of the first sector based on the positioning error of the second sector; determining whether a positioning error of the first sector exceeds the first threshold value, and stopping the write operation if the positioning error of the first sector exceeds the first threshold value; Magnetic disk device.

2. the controller registers both the positioning error in the inner circumferential direction and the positioning error in the outer circumferential direction; 2. The magnetic disk drive according to claim 1.

3. The controller setting a second threshold value for determining whether or not a positioning error of the first sector is registered; determining whether a positioning error of the first sector exceeds the second threshold, and registering the positioning error of the first sector if the positioning error of the first sector exceeds the second threshold; 2. The magnetic disk drive according to claim 1.

4. The controller setting a second threshold value for determining whether or not a positioning error of the first sector is registered; determining whether a positioning error of the first sector exceeds the second threshold; determining whether there is a registered positioning error in the first sector; determining whether the orientation of the positioning error of the first sector and the registered positioning error coincides in either the inner peripheral direction or the outer peripheral direction; determining whether the absolute value of the positioning error of the first sector is greater than the registered positioning error; registering the positioning error of the first sector when the positioning error of the first sector exceeds the second threshold, the registered positioning error exists, the directions of the positioning error of the first sector and the registered positioning error match, and the absolute value of the positioning error of the first sector is greater than the registered positioning error; 3. The magnetic disk drive according to claim 2.

5. The controller determining whether a positioning error of a third sector radially adjacent to the first sector has been registered; determining whether the direction of the positioning error of the third sector is toward the first sector; when the positioning error of the third sector is registered and the direction of the positioning error of the third sector is a direction toward the first sector, canceling the registration of the positioning error of the third sector; 2. The magnetic disk drive according to claim 1.

6. the first threshold value is a value obtained by subtracting a positioning error of the second sector from a predetermined track pitch narrowing margin; 2. The magnetic disk drive according to claim 1.

7. the first threshold value is a value obtained by subtracting a positioning error of the second sector from a predetermined track pitch narrowing margin, the predetermined track pitch narrowing margin is the sum of a positioning error of the first sector and a positioning error of the second sector, which are written to the first sector and the second sector, so that the third sector sandwiched between them has a read limit track width; 6. The magnetic disk drive according to claim 5.

8. The controller setting a third threshold value for allowing the write operation for the positioning error of the first sector when the positioning error of the second sector is not registered; determining whether a positioning error of the first sector exceeds the third threshold; stopping the write operation when the positioning error of the first sector exceeds the third threshold; 7. The magnetic disk drive according to claim 6.

9. the third threshold value is between half the track pitch narrowing margin and the track pitch narrowing margin; 9. The magnetic disk drive according to claim 8.

10. the first threshold value is a value obtained by adding a predetermined amount to a predetermined track pitch narrowing margin and subtracting the product of a predetermined gain and the positioning error of the second sector; 4. The magnetic disk drive according to claim 3.

11. the predetermined amount is the product of the predetermined gain minus 1 and the second threshold value; 11. The magnetic disk drive according to claim 10.

12. the first threshold value is a value obtained by subtracting the product of a predetermined gain and a positioning error of the second sector from a predetermined track pitch narrowing margin; 2. The magnetic disk drive according to claim 1.

13. The predetermined gain is a value of 1 or more.

13. The magnetic disk drive according to claim 10 or 12.

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