Magnetic disk device

Abstract

Embodiments provide a disk device capable of preventing imbalance in saving of control information. The disk device of the embodiments includes a plurality of disks, a plurality of heads provided corresponding to the plurality of disks to perform reading / writing of data to / from the disks, and a control section that controls the reading / writing of the heads. In addition, the plurality of disks each include a first saving section that saves control information related to the reading / writing of the heads. The control section switches the first saving section of a saving destination of first information from the disk to another disk, the first information being at least a part of the control information.

Description

[0001] This application claims the benefit of priority based on Japanese Patent Application No. 2021-48567 (filing date: March 23, 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] A known technique is to sequentially switch magnetic heads during tracking in a magnetic disk device so that the data reproduction time of multiple heads and the cumulative positioning data reproduction time during seek and tracking are equalized among the heads.

[0004] In a magnetic disk device, the control information stored on the magnetic disk is multiplexed for reliability. For example, in a dual or quadruple configuration, the control information is multiplexed and stored on multiple magnetic disks. The multiplexed control information is stored in a fixed location within a pre-set system area of ​​the magnetic disk. In addition, a process is also performed to alternately store the multiplexed control information in different areas. Regardless of the circumstances, the control information is stored in a specific magnetic head among a plurality of magnetic heads, and is stored on the magnetic disk via this head. Using a specific magnetic head to store the control information in this way causes the head to be used more frequently than other heads. Summary of the Invention

[0005] The embodiment provides a magnetic disk device capable of preventing imbalance in storage of control information.

[0006] A magnetic disk drive according to one embodiment includes: a plurality of magnetic disks; a plurality of magnetic heads, which are provided corresponding to the plurality of magnetic disks and read / write data from / to the magnetic disks; and a control unit, which controls the reading / writing of the magnetic heads. Furthermore, each of the plurality of magnetic disks includes a first storage unit, which stores control information related to the reading / writing of the magnetic heads. The control unit switches the first storage unit from storing first information, which is at least a portion of the control information, to another of the plurality of magnetic disks. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0008] Figure 2 This is a diagram showing an example of a group and a group according to this embodiment.

[0009] Figure 3This is a diagram showing an example of the configuration of a system area management unit according to this embodiment.

[0010] Figure 4 This is a flowchart showing an example of a process of switching a storage destination according to this embodiment.

[0011] Figure 5 This is a diagram for explaining the operation when the storage destination of control information according to this embodiment is changed.

[0012] Figure 6 This is a flowchart showing an example of a process of reading control information when the power is turned on according to this embodiment.

[0013] Figure 7 This is a flowchart showing an example of processing when the status according to this embodiment indicates an indeterminate state.

[0014] Figure 8 This is a flowchart showing an example of processing when information cannot be read from the system area management unit according to this embodiment. DETAILED DESCRIPTION

[0015] The following describes the embodiments with reference to the accompanying drawings. The disclosure is merely an example, and the invention is not limited by the contents described in the following embodiments. Any modifications that can be easily imagined by a person skilled in the art are naturally included in the scope of the disclosure. To make the description clearer, the dimensions and shapes of various parts are sometimes modified relative to the actual embodiment in the drawings to schematically represent them. In multiple drawings, corresponding elements are sometimes given the same reference numerals, and detailed descriptions are omitted.

[0016] Figure 1 This is a block diagram showing an example of the configuration of the magnetic disk device according to the present embodiment.

[0017] like Figure 1As shown, the magnetic disk device 1 is configured as, for example, a hard disk drive (HDD) and includes a magnetic disk 2, a spindle motor (SPM) 3, an actuator 4, a voice coil motor (VCM) 5, a magnetic head 10, a head amplifier IC 11, a R / W channel 12, a hard disk controller (HDC) 13, a microprocessor (MPU) 14, a driver IC 15, and a memory 16. Furthermore, the magnetic disk device 1 can be connected to a host computer (host) 17. The magnetic head 10 will be described in detail later, but includes a write head (recording head: writer) 10W, a read head (reproducing head: reader) 10R, and a spin-torque oscillator (STO) 100 as a high-frequency oscillation element. Alternatively, the R / W channel 12, HDC 13, and MPU 14 may be incorporated into a single-chip integrated circuit.

[0018] The magnetic disk 2 has, for example, a disk-shaped substrate made of a non-magnetic material. On each surface of the substrate, there are laminated in the following order: a soft magnetic layer made of a material exhibiting soft magnetic properties as a base layer, a magnetic recording layer having magnetic anisotropy in a direction perpendicular to the magnetic disk surface, and a protective film layer on the upper layer thereof. Here, the direction in which the magnetic head 10 is located is considered the upper layer.

[0019] The magnetic disk 2 is fixed to the spindle motor (SPM) 3 and rotated at a predetermined speed by the SPM 3. In addition, the number of magnetic disks 2 is not limited to one, and multiple magnetic disks 2 may be provided in the SPM 3. The SPM 3 is driven by a drive current (or drive voltage) supplied from the driver IC 15. The magnetic disk 2 records and reproduces data patterns through the magnetic head 10. The magnetic disk 2 has a system area (first storage unit) 200. The system area 200 stores first information (in this embodiment, the first information is control information related to writing), which is at least a part of the control information of the data of the magnetic head 10. In addition, the system area 200 has a system area management unit (second storage unit) 200a. The system area management unit 200a manages the control information. The system area 200 is provided, for example, at a part of the outermost circumference in the radial direction of the magnetic disk 2.

[0020] The actuator 4 is rotatably mounted and supports the magnetic head 10 at its front end. The actuator 4 is rotated by a voice coil motor (VCM) 5, thereby moving and positioning the magnetic head 10 on a desired track of the magnetic disk 2. The VCM 5 is driven by a drive current (or drive voltage) supplied from a driver IC 15.

[0021] The magnetic head 10 includes a slider, a write head 10W formed on the slider, and a read head 10R. A plurality of magnetic heads 10 are provided depending on the number of blocks of the magnetic disk 2 .

[0022] The head amplifier IC11 includes circuits related to driving the STO 100 and detecting oscillation characteristics. For example, the head amplifier IC11 includes an STO control unit 111, a recording coil control unit 112, a reproduction signal detection unit 113, and a heater control unit 114. The head amplifier IC11 performs functions such as driving the STO 100 and detecting drive signals. Furthermore, the head amplifier IC11 supplies a write signal (write current) corresponding to write data supplied from the R / W channel 12 to the write head 10W. Furthermore, the head amplifier IC11 amplifies the read signal output from the read head 10R and transmits it to the R / W channel 12.

[0023] The STO control unit 111 controls the current supplied to the STO 100 of the write head 10W. The recording coil control unit 112 includes a recording signal mode control unit and a recording current control unit. The recording coil control unit 112 controls the recording current supplied to the coil of the write head 10W based on the write signal. The reproduction signal detection unit 113 detects the signal (read data) reproduced by the read head 10R. The heater control unit 114 controls the power supply to the heater described later. In other words, the heater control unit 114 switches the heater on / off.

[0024] The R / W channel 12 is a signal processing circuit that processes signals related to reading and writing. It includes a read channel that processes read data and a write channel that processes write data. The R / W channel 12 converts read signals into digital data and demodulates the read data from the digital data. The R / W channel 12 encodes the write data transmitted from the HDC 13 and transmits the encoded write data to the head amplifier IC 11.

[0025] The HDC 13 controls the writing of data to and reading of data from the magnetic disk 2 via the magnetic head 10, the head amplifier IC 11, the R / W channel 12, and the MPU 14. The HDC 13 forms the interface between the magnetic disk device 1 and the host computer 17, controlling the transmission of read and write data. Specifically, the HDC 13 functions as a host interface controller that receives signals transmitted from the host computer 17 and transmits signals to the host computer 17. When transmitting signals to the host computer 17, the HDC 13 performs error correction processing on the reproduced signal read and demodulated by the magnetic head 10 in accordance with the MPU 14. Furthermore, the HDC 13 receives commands (such as write commands and read commands) transmitted from the host computer 17 and sends the received commands to the MPU 14.

[0026] The MPU 14 is the main controller (control unit) of the magnetic disk device 1 and performs servo control required for reading and writing operations and positioning the magnetic head 10. The MPU 14 also switches the storage location of control information. This process will be described in detail later.

[0027] The driver IC 15 controls the driving of the SPM 3 and the VCM 5 according to the control of the MPU 14. The VCM 5 is driven to position the magnetic head 10 toward a target track on the magnetic disk 2.

[0028] Memory 16 includes volatile memory and nonvolatile memory. For example, memory 16 includes a buffer memory formed of DRAM and a flash memory. Memory 16 stores programs and parameters required for processing by MPU 14. Memory 16 also includes a group switching count 161 and a group switching count 162. Group switching counts 161 and 162 are used when MPU 14 performs the process of switching the storage destination of control information, which will be described later. In this embodiment, the group switching count is set to 10,000 times and the group switching count is set to 1 time, but this is not limited to this.

[0029] Next, the groups and sets that manage control information related to the magnetic head 10 will be described. Figure 2 1 is a diagram showing an example of a group and a set. In this embodiment, the magnetic disk device 1 is described as having eight magnetic heads 10. However, the number of magnetic heads 10 is not limited to this.

[0030] like Figure 2 As shown, the magnetic disk device 1 has control information H1 to control information H8 corresponding to eight magnetic heads 10. The control information H1 to H8 are stored in the system area 200 of the magnetic disk 2 corresponding to each magnetic head 10, respectively.

[0031] Four groups, Group A through Group D, are defined. Group A consists of control information H1 and H2, Group B consists of control information H3 and H4, Group C consists of control information H5 and H6, and Group D consists of control information H7 and H8. Furthermore, Group S1 consists of control information H1 through H4 (Groups A and B), and Group S2 consists of control information H5 through H8 (Groups C and D). Thus, the control information H1 through H8 corresponding to the eight magnetic heads 10 consists of the four Groups A through D and the two Groups S1 and S2. Information defining these Groups A through D and Groups S1 and S2 is stored in, for example, memory 16.

[0032] When MPU 14 stores control information, the control information is stored in one of four groups A through D. At that time, the control information is replicated within each group. For example, if group A is the storage destination, control information H1 is stored in the system area 200 of disk 2. Then, the same control information H2 is stored in the system area 200 of another disk 2 within group A. In other words, control information H1 is replicated as control information H2. This replication and storage of control information provides redundancy, ensuring the reliability of disk drive 1.

[0033] Next, the system area management unit 200a will be described. Figure 3 This is a diagram showing an example of the configuration of the system area management unit 200a.

[0034] like Figure 3 As shown, in the system area management unit 200a, the status (Status) and the update count are associated with each of the eight heads 10 (head numbers SA-H1 to SA-H8). The head numbers SA-H1 to SA-H8 are associated with the control information H1 to H8 described above, respectively. The status stores status information indicating which group is to perform the control information saving process. In this embodiment, since the data is stored in group S1 or group S2, the status stores, for example, a state indicating that the data is a storage destination or a state indicating that the data is not a storage destination. In addition, if it is impossible to determine whether the data is a storage destination or not a storage destination for some reason, a state indicating that the storage destination is uncertain is stored. The update count stores the update count when the group is switched. In this embodiment, the same control information is stored in groups S1 and S2 (groups A, B, C, D), so the update count is transferred within groups S1 and S2 (that is, the same update count value does not exist in groups A, B, C, and D).

[0035] Next, a description will be given of a process for switching the storage location of the control information. Figure 4 This is a flowchart showing an example of a process for switching a save destination executed by the MPU 14. The following process is executed after the MPU 14 saves the control information in the currently set save destination.

[0036] The MPU 14 updates the update count (ST101). More specifically, the MPU 14 updates the update count of the head number set as the save destination in the system area management unit 200a. For example, when group A is set as the save destination, the update counts of the head numbers SA-H1 and SA-H2 are incremented.

[0037] Next, it is determined whether it is the group switching number (ST102). Specifically, the MPU 14 determines whether the update number after the update in step ST101 has reached the group switching number 161.

[0038] If it is determined that the number of group switching is not the number of group switching (ST102: No), the MPU 14 determines whether it is the number of group switching (ST103). Specifically, the MPU 14 determines whether the update number after the update in step ST101 has reached the number of group switching 162. In this embodiment, the number of group switching is set to 1, so the MPU 14 determines that it is the number of group switching. Alternatively, if the number of group switching is set to multiple times, for example, the MPU 14 can determine whether the update number has reached the number of group switching 162 based on the difference between the update number after the update in step ST101 and the update number of the switching target group.

[0039] If it is determined that the number of group switchings has been reached (ST103: YES), the MPU 14 switches the group (ST104). This switching is performed within the group. For example, after group A has stored control information, if a group switch is determined, the MPU 14 switches the storage destination of the control information from group A to group B.

[0040] Then, MPU 14 sets the switched group as the destination for control information storage (ST105). In the case described above, group B becomes the destination for control information storage. Therefore, when control information is subsequently stored, it is stored in the switched group. If it is determined that the number of group switching attempts has not been reached (ST103: No), MPU 14 terminates this processing.

[0041] On the other hand, if it is determined that the number of group switching has occurred (ST102: YES), the MPU 14 switches the group to which the control information is to be saved (ST106). For example, if group S1 is set as the save destination, and if it is determined that the number of group switching has occurred, the save destination of the control information is switched to group S2. The MPU 14 then updates the system area management unit 200a (ST107). For example, if group S2 has been switched and set as the save destination of the control information, the MPU 14 sets the status of the head numbers SA-H5 to SA-H8 to indicate that they are the save destination of the control information, and sets the status of SA-H1 to SA-H4 to indicate that they are not the save destination of the control information, and ends the process.

[0042] Next, the operation when the storage location of the control information is changed will be described. Figure 5 This is a diagram for explaining this effect.

[0043] exist Figure 5 In the example, when the control information storage process for group A of group S1 is completed, the control information storage process is then performed for group B of group S1. Furthermore, the control information storage process is then performed for group A. This process is repeated until the number of group switching times (10,000 times in this embodiment) is reached, and the group is switched this time. At this time, information indicating the switched group that will be the storage destination of the control information is stored in the status of the system area management unit 200a. In the case described above, information indicating that the status of groups C and D is the storage destination of the control information is stored, and information indicating that the status of groups A and B is not the storage destination of the control information is stored.

[0044] Thus, in this embodiment, the group where the control information is stored is switched at a frequency of once every 10,000 group switches. Consequently, the magnetic disk drive 1 can reduce the number of times it stores control information in the system area management unit 200a. Consequently, by storing information in the system area management unit 200a, the magnetic disk drive 1 can incur almost no additional overhead in terms of storage processing time.

[0045] Furthermore, the storage destinations of control information for groups A and B (or groups C and D) are switched alternately. Therefore, if the latest data cannot be read, the previous data can be pre-read based on historical records. For example, it can be assumed that MPU 14 pre-stores information related to the previous data in memory 16. This reduces the difficulty of recovery in the event of a failure in magnetic disk drive 1.

[0046] Furthermore, when the power supply (not shown) of the magnetic disk drive 1 is turned on, the MPU 14 first reads the information from the system area management unit 200a. This allows the MPU 14 to determine whether the group to be read from each piece of control information is group S1 (groups A and B) or group S2 (groups C and D). Consequently, the number of control information items required for data reading from the system area 200 can be limited to four. This limitation allows the magnetic disk drive 1 to minimize the processing time required to read the control information when the power supply is turned on.

[0047] Figure 6 FIG. 1 is a flowchart showing an example of a process of reading control information when the power is turned on. Figure 6As shown, when the MPU 14 determines that the power of the magnetic disk drive 1 is on (ST201: YES), it refers to the system area management unit 200a and obtains the group set as the save destination (ST202). The MPU 14 confirms the status of each SA-H1 to SA-H8 in the system area management unit 200a to obtain information about the group set as the save destination. Next, the MPU 14 obtains control information from the group set as the save destination (ST203). In this way, the four pieces of control information for the group set as the save destination are obtained.

[0048] In addition, for some reason, the state of the system area management unit 200a may become the indeterminate state as described above. Figure 7 This is a flowchart showing an example of processing when the MPU 14 reads the status of the system area management unit 200 a and the status indicates an indeterminate state.

[0049] like Figure 7 As shown, when the status information indicates an indeterminate state (ST301: YES), the MPU 14 reads the update counts of all the head numbers SA-H1 to SA-H8 of the system area management unit 200a (ST302), and based on the update counts, identifies the head 10 having the latest update count information (ST303), and updates the status (ST304). Thus, the indeterminate state is eliminated, and the state is set so that the group including the head number with the latest update count becomes the group where the control information is stored.

[0050] Furthermore, for some reason, there may be a case where information cannot be read from the system area management unit 200a. Figure 8 This is a flowchart showing an example of processing when information cannot be read from the system area management unit 200a.

[0051] like Figure 8 As shown, when information cannot be read from the system area management unit 200a (ST401: YES), the MPU 14 reads control information from the system area 200 of all head numbers SA-H1 to SA-H8 (in other words, group A to group D) (ST402), and reconstructs the system area management unit 200a based on the read control information (ST403). Thus, even when information cannot be read from the system area management unit 200a, the magnetic disk device 1 can reconstruct the system area management unit 200a.

[0052] As described above, according to the magnetic disk device 1, whenever the control information is repeatedly stored in the system area 200, the magnetic head 10 used for storing the control information is switched. Therefore, the imbalance in the frequency of use of the magnetic head 10 having the STO 100 can be eliminated. In this way, the magnetic disk device 1 can avoid the imbalance in the frequency of use of the magnetic head 10 during the write operation, and can extend the life of the magnetic head 10.

[0053] Furthermore, in the magnetic disk device 1, the system area management unit 200a saves the state of the group S1 and S2 only once per 10,000 group switches. This reduces the frequency of save processing and prevents an increase in save overhead.

[0054] Furthermore, the magnetic disk device 1 performs processing such that the history data immediately preceding the latest data being stored is stored. This allows the magnetic disk device 1 to reduce the difficulty of recovery in the event of a failure.

[0055] Furthermore, the magnetic disk device 1 only needs to read the control information of either group S1 or S2 when the power is turned on. Therefore, the magnetic disk device can reduce the processing time required for reading the system information when the power is turned on.

[0056] Furthermore, in the above embodiment, the auxiliary unit provided by the magnetic disk drive 1 and used to assist data writing is described as employing a microwave-assisted method such as the STO 100. However, the present invention is not limited thereto. For example, the auxiliary unit may also employ a thermal-assisted method. Even when the magnetic disk drive 1 includes a thermal-assisted auxiliary unit, the same effects as those of the above embodiment can be achieved.

[0057] In addition, several embodiments of the present invention have been described, 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 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: Multiple disks; a plurality of magnetic heads, which are provided corresponding to the plurality of magnetic disks and read / write data from / to the magnetic disks; and a control unit that controls the reading / writing of the magnetic head, Each of the plurality of magnetic disks includes a first storage unit, and the first storage unit stores control information related to the reading / writing of the magnetic head. The control unit switches the first storage unit as a storage destination of first information from one of the plurality of disks to another of the plurality of disks, wherein the first information is at least a part of the control information. The plurality of disks are divided into a plurality of groups, The control unit switches the storage destination in the group every time the control information is stored. The control unit switches the storage destination from a certain group to another group when the number of times the control information is stored reaches a predetermined value.

2. The magnetic disk device according to claim 1, A second storage unit is provided for storing, when the control unit switches the group of the storage destination, state information indicating the switched group as the storage destination.

3. The magnetic disk device according to claim 2, The multiple disks constituting the group are further divided into multiple groups within one group. The control unit switches the storage destination of the control information so that update frequency data indicating an update status of the control information of the plurality of groups in each of the groups differs.

4. The magnetic disk device according to claim 3, The second storage unit stores, in addition to the state information indicating the switched group as the storage destination, update count information indicating the number of updates to the group.

5. The magnetic disk device according to claim 4, When the control unit fails to obtain information indicating the group corresponding to the latest update count information from the second storage unit, the control unit obtains the update count information of the group from the first storage unit, and restores the information stored in the second storage unit based on the obtained update count information of the group.

6. The magnetic disk device according to claim 4, When the control unit cannot read the information from the second storage unit, the control unit obtains the control information from each of the first storage units and reconstructs the information stored in the second storage unit.

7. The magnetic disk device according to claim 2, When the magnetic disk drive is powered on, the control unit first acquires the information stored in the second storage unit.

8. The magnetic disk device according to claim 1, The first information includes information related to writing by the magnetic head.

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