disk device

Abstract

A magnetic disk device capable of improving data recording performance is provided. The magnetic disk device includes: a magnetic disk; a magnetic head; a power supply unit that supplies power to the magnetic head; a control unit that controls reading and writing data from the magnetic disk and, when writing data, suppresses the magnetic field range of the write head based on the offset of the write head; and an address storage unit that stores the address of the magnetic disk where data was written with the magnetic field range suppressed. The control unit reads data from the magnetic disk using the read head at a predetermined timing based on the address stored in the address storage unit, and writes the read data to the magnetic disk using the write head without suppressing the magnetic field range.

Description

[0001] This application claims the benefit of priority based on Japanese Patent Application No. 2021-115887 (filing date: July 13, 2021), the entire contents of which are incorporated herein by reference. Technical Field

[0002] The embodiment relates to a magnetic disk device. Background Art

[0003] Magnetic disk devices are required to have larger storage capacities. Therefore, in order to increase the capacity of magnetic disk devices, the track pitch of the magnetic disk is narrowed to increase the recording density. Summary of the Invention

[0004] When the recording density of the magnetic disk is increased as described above, the storage capacity of the magnetic disk device can be increased. This allows for a larger storage capacity, but on the other hand, it also increases the influence of the magnetic field on adjacent tracks when recording data. Specifically, when the magnetic disk device is subjected to certain external vibrations (shocks) while recording data, the write head will swing on the track. Sometimes this swing width (offset) becomes large and damages the data on adjacent tracks. To prevent this, a threshold is set for the offset, and if this threshold is exceeded, data recording is prohibited. In the case of a single vibration (shock), data can be recorded after the magnetic disk rotates once, but in the case of long-term vibrations (shocks), the state in which data recording is not allowed will continue. As a result, the data recording performance of the magnetic disk device will deteriorate.

[0005] An object of the embodiment is to provide a magnetic disk device capable of improving data recording performance.

[0006] A magnetic disk drive according to one embodiment includes: a magnetic disk; a magnetic head including a read head for reading data from the magnetic disk, a write head for writing data to the magnetic disk, and a heater for adjusting the amount of levitation of the read and write heads relative to the magnetic disk; a power supply unit for supplying power to the read and write heads, and the heater; a control unit for controlling reading and writing data from the magnetic disk and, when writing data, suppressing the magnetic field range of the write head according to an offset of the write head; and an address storage unit for storing the address of the magnetic disk to which data has been written with the magnetic field range suppressed. The control unit reads data from the magnetic disk at a predetermined timing based on the address stored in the address storage unit, and writes the read data to the magnetic disk via the write head without suppressing the magnetic field range. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1This is a diagram showing an example of the configuration of a magnetic disk device according to this embodiment.

[0008] Figure 2 This is a diagram showing an example of information stored in the volatile memory according to the present embodiment.

[0009] Figure 3 This is a diagram showing an example of status information stored in the system area according to this embodiment.

[0010] Figure 4 This is a diagram for explaining an example of magnetic field suppression control for suppressing a magnetic field generated when writing data according to the present embodiment.

[0011] Figure 5 This is a diagram for explaining an example of magnetic field suppression control for suppressing a magnetic field generated when writing data according to the present embodiment.

[0012] Figure 6 This is a diagram for explaining an example of magnetic field suppression control for suppressing a magnetic field generated when writing data according to the present embodiment.

[0013] Figure 7 This is a flowchart showing an example of processing executed by the MPU when writing data according to this embodiment.

[0014] Figure 8 This is a diagram for explaining an example of magnetic field suppression control and a write state according to an offset threshold value according to another embodiment.

[0015] Figure 9 This is a diagram for explaining an example of magnetic field suppression control and a write state according to an offset threshold value according to the present embodiment.

[0016] Figure 10 This is a flowchart showing an example of data rewriting processing executed by the MPU involved in the embodiment.

[0017] Description of labels

[0018] 1 Magnetic disk, 2 Spindle motor, 3 Actuator, 4 Voice coil motor, 10 Magnetic head, 10 W write head, 10 R read head, 20 Servo combo, 30 Head amplifier IC, 40 R / W channel, 50 HDC, 60 MPU, 70 Volatile memory, 71 First threshold storage unit, 72 Second threshold storage unit, 73 Management information storage unit, 100 System area, 102 Status information storage unit, 200 Magnetic disk device, HE heater DETAILED DESCRIPTION

[0019] The following describes the embodiments with reference to the accompanying drawings. In addition, the disclosure is merely an example, and the invention is not limited by the contents described in the following embodiments. Deformations that can be easily thought of by those skilled in the art are of course included in the scope of the disclosure. In order to make the description clearer, the dimensions, shapes, etc. of each part are sometimes changed relative to the actual implementation scheme in the drawings and are shown in a schematic manner. In multiple drawings, the same reference numerals are sometimes given to corresponding elements, and detailed descriptions are omitted.

[0020] Figure 1 This is a diagram showing an example of the configuration of a magnetic disk device according to an embodiment.

[0021] like Figure 1 As shown, the magnetic disk drive 200 is configured as, for example, a hard disk drive (HDD) and includes a magnetic disk 1, a spindle motor (SPM) 2, an actuator 3, a voice coil motor (VCM) 4, a magnetic head 10, a servo assembly (SVC) 20, a head amplifier IC 30, a R / W channel 40, a hard disk controller (HDC) 50, a microprocessor (MPU) 60, a volatile memory 70, and a non-volatile memory 80. Furthermore, the magnetic disk drive 200 can be connected to a host system 150. The magnetic head 10 includes a write head 10W, a read head 10R, and a heater HE. The servo assembly 20, the R / W channel 40, the HDC 50, and the MPU 60 can also be incorporated into a single-chip integrated circuit.

[0022] The magnetic disk 1 has, for example, a disk-shaped substrate made of a non-magnetic material. On each surface of the substrate, a soft magnetic layer (forming a base layer) made of a material exhibiting soft magnetic properties, a magnetic recording layer (located above the soft magnetic layer and having magnetic anisotropy in a direction perpendicular to the disk surface), and a protective film layer (located above the magnetic recording layer) are stacked in the order described above. Here, the direction of the magnetic head 10 is set to the upper layer.

[0023] The magnetic disk 1 is fixed to a spindle motor (SPM) 2 and rotated at a predetermined speed by the SPM 2. Furthermore, the number of magnetic disks 1 is not limited to one; multiple magnetic disks 1 may be provided on the SPM 2. The SPM 2 is driven by a drive current (or drive voltage) supplied from a servo assembly unit 20. The magnetic disk 1 records and reproduces data patterns via a magnetic head 10. The magnetic disk 1 includes a system area 100 and a data area 110. The system area 100 includes a status information storage unit 102, which stores the status of the disk surface of the magnetic disk 1, which will be described in detail later. The system area 100 is provided, for example, at the outermost or innermost portion of the radial direction of the magnetic disk 1. The data area 110 stores data.

[0024] The actuator 3 is rotatably mounted and supports the magnetic head 10 at its front end. The magnetic head 10 is moved and positioned on a desired track on the magnetic disk 1 by rotating the actuator 3 using a voice coil motor (VCM) 4. The VCM 4 is driven by a drive current (or drive voltage) supplied from a servo assembly 20.

[0025] As described above, the magnetic head 10 includes a write head 10W and a read head 10R. The write head 10W writes data to the magnetic disk 1. The read head 10R reads data from the magnetic disk. The heater HE adjusts the flying distance (in other words, the gap) of the write head 10W or the read head 10R relative to the disk surface.

[0026] The servo assembly 20 includes a servo control unit 21 and a spindle motor control unit 22. The servo control unit 21 controls the voice coil motor 4 according to the control of the MPU 60 and detects the head position information of the magnetic head 10. This detected head position information is output to the MPU 60. In this embodiment, the head position information includes information indicating the offset amount by which the position of the write head on the magnetic disk 1 has deviated from the target position to be positioned. The spindle motor control unit 22 controls the spindle motor 2 according to the control of the MPU 60. The voice coil motor 4 is driven to position the magnetic head 10 toward the target track on the magnetic disk 1.

[0027] The head amplifier IC (power supply unit) 30 supplies a write signal (write current) corresponding to the write data supplied from the R / W channel 40 to the write head 10W. Furthermore, the head amplifier IC 30 amplifies the read signal output from the read head 10R and transmits it to the R / W channel 40. Furthermore, the head amplifier IC 30 adjusts the amount of levitation of the write head 10W or the read head 10R relative to the disk surface 1 by adjusting the voltage applied to the heater HE.

[0028] The R / W channel 40 is a signal processing circuit that processes signals related to reading (read) and writing (write). The R / W channel 40 includes a read channel that processes read data signals and a write channel that processes write data signals. The R / W channel 40 converts the read signal input from the read head 10R via the head amplifier IC 30 into digital data and demodulates the read data from the digital data. The R / W channel 40 encodes the write data transmitted from the HDC 50 and transmits the encoded write data to the write head 10W via the head amplifier IC 30.

[0029] The HDC 50 includes an interface control unit 51, a cache control unit 52, a disk control unit 53, and a command control unit 54. Furthermore, the HDC 50 controls the writing of data to and the reading of data from the magnetic disk 1 via the magnetic head 10, the servo assembly 20, the head amplifier IC 30, the R / W channel 40, and the MPU 60. More specifically, the interface control unit 51 forms an interface between the magnetic disk device 200 and the host system 150. The cache control unit 52 temporarily stores commands transmitted from and to the interface control unit 51 in the cache 90. The disk control unit 53 writes data to and processes data read from the magnetic disk 1. The command control unit 54 controls the commands transmitted from the cache control unit 52. Through these control units, the HDC 50 functions as a host interface controller that receives signals transmitted from and to the host system 150. Furthermore, the HDC 50 receives commands (write commands, read commands, etc.) transmitted from the host system 150 , and sends the received commands to the MPU 60 .

[0030] The MPU 60 is a main controller of the magnetic disk device 200 and includes a read / write control unit 61 and a position detection unit 62. The read / write control unit 61 controls read / write operations. The position detection unit 62 detects the position of the magnetic head 10 based on head position information output from the SVC 20.

[0031] The volatile memory 70 is, for example, a DRAM. Figure 2 The information stored in the volatile memory 70 will be described later. The non-volatile memory 80 is, for example, a flash ROM. The non-volatile memory 80 stores, for example, programs required for the processing of the MPU 60. For details of the program contents, refer to Figure 7 、 Figure 10 This will be described later.

[0032] Figure 2 It is a diagram showing an example of information stored in the volatile memory 70 .

[0033] like Figure 2 As shown, the volatile memory 70 includes a first threshold storage unit 71, a second threshold storage unit 72, and a management information storage unit 73. The first threshold storage unit 71 stores a first threshold. The first threshold is a value indicating the amount of offset that would damage the data stored in the adjacent track due to the influence of data writing by the write head 10W in a normal suspended state. The second threshold storage unit 72 stores a second threshold. The second threshold is an offset greater than the first threshold and is a value indicating the amount of offset that would damage the data stored in the adjacent track even if reference is made to the first threshold. Figures 4 to 6In the data writing based on the magnetic field suppression control described later, the offset value indicates the amount of data stored in adjacent tracks damaged by the influence of the data writing. Furthermore, regarding the first and second threshold values, for example, when the magnetic disk drive 200 is powered on, the first and second threshold values ​​stored in any location within the magnetic disk drive 200 are stored in the first threshold storage unit 71 and the second threshold storage unit 72, respectively. The management information storage unit 73 stores management information. The management information is information indicating the address of the data written by executing the magnetic field suppression control.

[0034] Figure 3 102 is a diagram showing an example of status information stored in the system area 102 .

[0035] The status information is information indicating the status of the disk surface of the disk 1. Figure 3 As shown, status information 102a is stored in association with the address of data area 110 of magnetic disk 1. In this embodiment, status information 102a indicates three states of the disk surface: normal, uneven surface, and convex. Normal indicates that the disk surface is properly formed. Uneven surface indicates that the disk surface is formed in a state where the magnetic field easily changes. Concave indicates that the disk surface is formed as a protrusion. In this way, the state of the disk surface is stored in association with the address of data area 110. Furthermore, status information 102a is generated based on the results of a disk surface inspection of magnetic disk 1, for example, during pre-shipment inspection, and stored in status information storage unit 102 of system area 100.

[0036] Figures 4 to 6 This is a diagram for explaining an example of magnetic field suppression control for suppressing a magnetic field generated when writing data. Figures 4 to 6 The magnetic field is suppressed under each of conditions C1 to C3. This magnetic field suppression is performed when, for example, vibration is applied during data writing and displacement of the magnetic head 10, more specifically, the write head 10W, occurs.

[0037] Figure 4 This is a diagram showing an example of the suppressive effect of the magnetic field under condition C1.

[0038] Condition C1 is a case where the floating amount of the write head 10W is reduced. In other words, the floating amount is the distance between the write head 10W and the disk surface 1. The adjustment of the floating amount is performed by applying a signal from the head amplifier IC 30 to the heater HE (in the vicinity of the heater HE) provided in the magnetic head 10 and near the write head 10W based on the instruction of the MPU 60. Figure 4 This is achieved by changing the voltage (omitted in the figure). Figure 4As shown, when the write head 10W is normally at position P1 during data writing, the write spread width of the write head 10W is set to width W1. In other words, when the write head 10W is at position P2, which is shortened from the disk surface, the write spread width becomes width W2 (< W1). Thus, by reducing the write head 10W's float distance from position P1 to position P2, the write spread width can be narrowed. Therefore, under condition C1, the magnetic disk drive 200 can suppress the magnetic field generated during data writing.

[0039] Figure 5 This is a diagram showing an example of the effect of magnetic field suppression under condition C2.

[0040] Condition C2 is a case where the current (or voltage) supplied to the write head 10W is reduced. The adjustment of the current supplied to the write head 10W is achieved by changing the current value supplied from the head amplifier IC 30 to the write head 10W based on the instruction of the MPU 60. Figure 5 As shown, when writing data, the write spread width of the write head 10W is set to width W1 when a normal current is supplied to the write head 10W. However, when the current supplied to the write head 10W is reduced, the write spread width becomes width W3 (< W1). Thus, by reducing the current supplied to the write head 10W, the write spread width can be narrowed. Therefore, under condition C2, as with condition C1, magnetic disk drive 200 can suppress the magnetic field generated during data writing.

[0041] Figure 6 This is a diagram showing an example of the effect of magnetic field suppression under condition C3.

[0042] Condition C3 reduces the amount of levitation of the write head 10W and the current (or voltage) supplied to the write head 10W. This is a combination of Conditions C1 and C2. By reducing the amount of levitation of the write head 10W from position P1 to position P2 and reducing the current supplied to the write head 10W, the write spread width can be narrowed. Therefore, under Condition C3, as with Conditions C1 and C2, magnetic disk drive 200 can suppress the magnetic field generated during data writing.

[0043] In addition, refer to Figures 4 to 6 The described suspension amount of the write head 10W and the current value supplied to the write head 10W can be set according to the medium characteristics of the disk 1 (normal, surface unevenness already described), medium protrusions (convex parts already described), suspension margin, writability, etc.

[0044] Next, the processing when writing data will be described. Figure 7 This is a flowchart showing an example of processing executed by the MPU 14 when writing data.

[0045] like Figure 7 As shown, upon receiving a host command (a write command in this embodiment) (ST101), the MPU 60 determines whether the head position information is within the first threshold (ST101). Specifically, the MPU 60 determines whether the offset from the target position included in the head position information is within the first threshold stored in the first threshold storage unit 71. If it is determined to be within the first threshold (ST102: Yes), the MPU 60 writes the data (ST103) and issues a host response (ST104). In other words, the MPU 60 sends a write completion message to the host system 150.

[0046] On the other hand, when it is determined that the head position information is not within the first threshold value (ST102: No), the MPU60 determines whether the head position information is within the second threshold value (ST105). Specifically, the MPU60 determines whether the offset from the target position included in the head position information is within the second threshold value stored in the second threshold value storage unit 72. When it is determined that it is within the second threshold value (ST105: Yes), the MPU60 performs magnetic field suppression control (ST106). That is, using the reference Figures 4 to 6 In any of the methods under Conditions C1 to C3 described above, control is performed to suppress the magnetic field during data writing.

[0047] Here, how to select the conditions C1 to C3 will be described. In this embodiment, the MPU 60 selects the condition C1 to C3 based on the state information 102a stored in the state information storage unit 102 (see Figure 3 ), selecting one of conditions C1 to C3. For example, when writing data to a convex area, the MPU 60 selects condition C2. This is to prevent the write head 10W from contacting the protrusions in that area. This allows the magnetic field suppression control to be set according to the surface condition of the magnetic disk 1.

[0048] After executing magnetic field suppression control in this manner, the MPU 60 writes data (ST107). Next, the MPU 60 registers the address (ST108). Specifically, the MPU 60 stores the address of the data written by executing magnetic field suppression control in the management information storage unit 73. Next, the MPU 60 cancels magnetic field suppression control (ST109) and performs a host response (ST104).

[0049] If the MPU 60 determines that the head position information is not within the second threshold (ST105: No), the MPU 60 stops writing (ST110). Furthermore, the MPU 60 waits for the magnetic disk 1 to rotate (ST111) and determines whether the head position information is within the second threshold (ST112). If the MPU 60 determines that the head position information is within the second threshold (ST112: Yes), the process proceeds to step ST106 described above. The MPU 60 performs magnetic field suppression control and then writes data (ST106 to ST109, ST104).

[0050] If the head position information is determined not to be within the second threshold (ST112: No), the MPU 60 waits for the disk 1 to rotate (ST113) and then determines whether the head position information is within the first threshold (ST114). If it is determined to be within the first threshold (ST114: Yes), the process proceeds to step ST103 described above, where the MPU 60 writes data (ST103) and sends a write completion message to the host (ST104). If it is determined not to be within the first threshold (ST114: No), the MPU 60 terminates the process.

[0051] Next, an example of magnetic field suppression control and a write state according to the offset threshold value will be described. Figure 8 In the case of other embodiments that do not apply the technology of this embodiment, Figure 9 This is the case in this embodiment.

[0052] First, another embodiment will be described. In another embodiment, the threshold value for prohibiting writing of the offset amount by the write head 10W is one.

[0053] As shown by the label T1, the write head position, suspension (constant), and IW (current) (constant) are represented according to the write (WT) state. As the write state, the state T11 in which WT is allowed, the state T12 in which write is allowed to deviate, and the state T13 in which the offset exceeds the write prohibition threshold are represented. The write head 10W is located at an arbitrary track Trk(n), and the track Trk(n+1) is adjacent to the track Trk(n). In addition, the magnetic field B represents the range of the magnetic field of the write head 10W. Suspension is the amount of suspension of the write head 10W, and current is the amount of current flowing in the write head 10W. In this other embodiment, magnetic field suppression control is not performed, and therefore, each is constant.

[0054] like Figure 8As shown, in state T11, when write is enabled, the track width of track Trk(n) and the range of magnetic field B are roughly the same. Sometimes, when writing data, the disk drive is subjected to some shock, causing the write head 10W to deviate. When this deviation does not exceed the threshold, as in state T12, when write is enabled and deviated, the range of magnetic field B deviates from the track width of track Trk(n) and slightly includes the track width of track Trk(n+1). Because the deviation is slight, it has no effect on track Trk(n+1). However, when the deviation exceeds the threshold, as in state T13, when the write disable threshold is exceeded, the range of magnetic field B deviates significantly from the track width of track Trk(n) and considerably includes the track width of track Trk(n+1). This can affect the adjacent track Trk(n+1), potentially damaging the data stored in track Trk(n+1). To prevent this, data recording is prohibited when the deviation exceeds the threshold. However, if such vibrations continue, the state in which data recording is not permitted in the magnetic disk device will continue, and the data recording performance will be significantly deteriorated.

[0055] Next, the present embodiment will be described. In the present embodiment, the threshold value of the offset amount of the write head 10W is two threshold values: the first threshold value and the second threshold value, as described above.

[0056] As shown by reference numeral T2, similarly to the case of reference numeral T1, the write head position, suspension (constant), and IW (current) (constant) are indicated according to the write (WT) state. As write states, the state T21 in which WT is allowed, the state T22 in which write is allowed to deviate, the state T23 in which the first write-allowed threshold value deviates, and the state T24 in which the second write-inhibited threshold value deviates are indicated. The position of the write head 10W is located at an arbitrary track Trk(n), and the track Trk(n+1) is adjacent to the track Trk(n). In addition, Figure 8 Similarly, in the case of , magnetic field B represents the range of the magnetic field of the write head 10W, levitation is the amount of levitation of the write head 10W, and current is the amount of current supplied to the write head 10W.

[0057] like Figure 9 As shown, in the write-enabled state T21, the track width of the track Trk(n) and the range of the magnetic field B are roughly consistent. In the write-enabled offset state T22, the range of the magnetic field B deviates from the track width of the track Trk(n) and slightly includes the track width of the track Trk(n+1). This is consistent with the Figure 8The same applies to the case. In the case of state T23 where the write permission first threshold is exceeded, the offset exceeds the first threshold, and therefore, the range of the magnetic field B deviates from the track width of track Trk(n) and includes the track width of track Trk(n+1). However, the suspension amount of the write head 10W is reduced, that is, the distance to the disk surface of the magnetic disk 1 becomes closer, and therefore, the influence of the magnetic field is suppressed. In addition, instead of adjusting the suspension amount of the write head 10W or together with the adjustment of the suspension amount of the write head 10W, it is also possible to adjust the current supplied to the write head 10W in a manner that reduces. In this way, when the offset of the write head 10W exceeds the first threshold, by performing magnetic field suppression control, even if it exceeds the first threshold, it will not affect the adjacent track Trk(n+1), and data can be written. When the offset becomes larger and reaches state T24 exceeding the write prohibition second threshold offset, the deviation from the track width of track Trk(n) becomes larger. Even if magnetic field suppression control is performed, the range of the magnetic field B also largely includes the track width of track Trk(n+1), and therefore, the processing of prohibiting data recording is performed.

[0058] As described above, even if the offset exceeds the first threshold, the magnetic disk drive 200 can continue writing data by executing magnetic field suppression control until the offset exceeds the second threshold.

[0059] Next, the process of rewriting data will be explained. As already described, when the magnetic disk drive 200 is subjected to vibration, for example, and the deflection of the write head 10W exceeds the first threshold value but is within the second threshold value, data is written using magnetic field suppression control. In this case, since data is written using magnetic field suppression control, the data writing quality may deteriorate compared to normal writing. Therefore, the magnetic disk drive 200 performs a process of reading the data and then writing the read data. Figure 10 1 is a flowchart showing an example of data rewriting processing executed by the MPU 60. In the present embodiment, this processing is executed in the idle state.

[0060] In the idle state, the MPU 60 determines whether management information is stored (ST201). More specifically, in the idle state, the MPU 60 refers to the management information storage unit 73 to confirm whether management information is stored. If it is determined that management information is stored (ST201: Yes), the MPU 60 reduces the flying height of the read head 10R compared to normal (ST202). With the flying height of the read head 10R thus reduced, data is read (ST203). In other words, the MPU 60 reads data from the disk 1 based on the address (area) stored in the management information.

[0061] Next, the MPU 60 writes data based on the management information (ST204). The MPU 60 writes the data read from the address stored in the management information to the data area 110. Next, the MPU 60 returns the floating height of the read head 10R to normal (ST205). In this state, the MPU 60 performs a read operation (ST206). Specifically, the MPU 60 checks whether the written data can be read at the normal floating height.

[0062] Next, the MPU 60 clears the management information (ST207). After clearing the management information stored in the management information storage unit 73, the idle state is restored. If it is determined in step ST201 described above that no management information is stored (ST201: No), the idle state continues.

[0063] As described above, the magnetic disk device 200 can rewrite the data written by the magnetic field suppression control. Therefore, the magnetic disk device 200 can improve the writing quality of the data. In addition, the rewriting of the data is performed in the idle state, so the processing burden of the magnetic disk device 200 can be reduced. In addition, the rewriting of the data can also be performed when the processing burden of the magnetic disk device 200 is light even when the data is not in the idle state. Furthermore, the rewriting process of the data can also be forcibly performed at a predetermined timing. The predetermined timing in this case is, for example, the timing before performing the so-called refresh process.

[0064] In the above embodiment, the magnetic disk device 200 has two thresholds, the first threshold and the second threshold, as thresholds for determining whether to execute magnetic field suppression. However, the present invention is not limited thereto. Three or more thresholds may be used to change magnetic field suppression control at different stages.

[0065] In addition, several embodiments of the present invention have been described above, but these embodiments are provided as examples and are not intended to limit the scope of the invention. These new embodiments can be implemented in various other ways and can be omitted, replaced, or modified without departing from the scope of the invention. These embodiments and / or their variations are included within the scope and spirit of the invention and are included within the scope of the invention described in the claims and their equivalents.

Claims

1. A magnetic disk device comprising: disk; a magnetic head including a read head for reading data from the magnetic disk, a write head for writing data to the magnetic disk, and a heater for adjusting the amount of suspension of the read head and the write head relative to the magnetic disk; a power supply unit that supplies power to the read head, the write head, and the heater; a control unit that controls reading / writing of data from / to the magnetic disk and, when writing the data, suppresses a magnetic field range of the write head according to an offset of the write head; a threshold storage unit storing a first threshold defining the offset amount and a second threshold greater than the first threshold; as well as an address storage unit that stores an address of the magnetic disk to which data is written while suppressing the magnetic field range; The control unit reads data from the magnetic disk using the read head based on the address stored in the address storage unit at a predetermined timing, and writes the read data to the magnetic disk using the write head without suppressing the magnetic field range. When writing data, the control unit continues writing the data while suppressing the magnetic field until the magnetic field exceeds the first threshold and before the magnetic field exceeds the second threshold, and prohibits writing the data when the magnetic field exceeds the second threshold.

2. The magnetic disk device according to claim 1, The control unit controls the power supply unit to adjust the voltage applied to the heater, thereby adjusting the amount of levitation of the write head relative to the magnetic disk, thereby suppressing the magnetic field when writing the data.

3. The magnetic disk device according to claim 1, The control unit controls the power supply unit to adjust the current supplied to the write head, thereby suppressing the magnetic field when writing the data.

4. The magnetic disk device according to claim 1, A state information storage unit is provided for storing state information indicating the state of the disk surface. The control unit changes the magnetic field suppression based on the status information stored in the status information storage unit for the region where the data is written.

5. The magnetic disk device according to claim 4, The state information storage unit is provided on the magnetic disk.

6. The magnetic disk device according to claim 4, The state information includes information indicating surface unevenness and convex portions.

7. The magnetic disk device according to claim 1, When reading data from the magnetic disk through the read head based on the address stored in the address storage unit, the control unit adjusts the voltage applied to the heater, thereby reducing the amount of suspension of the read head relative to the magnetic disk surface compared to when reading other data.

8. The magnetic disk device according to claim 1, The predetermined timing is when the magnetic disk device is in an idle state.

9. The magnetic disk device according to claim 1, When the read data is written to the magnetic disk by the write head without performing magnetic field suppression, the address corresponding to the data stored in the address storage unit is cleared.

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