This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2019-161450, filed Sep. 4, 2019, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a magnetic disk device and a method of controlling the magnetic disk device.
As an example of a technique for increasing a recording density and a recording capacity of a magnetic disk device, high frequency assisted recording (MAMR: Microwave Assisted Magnetic Recording) is known. In the MAMR, a magnetic head having a recording magnetic pole (main magnetic pole) and a high-frequency oscillation element is used. The recording magnetic pole is excited by a recording current applied thereto and generates a recording magnetic field. The high-frequency oscillation element generates a high-frequency magnetic field when energized. The generated high-frequency magnetic field is applied to a disk and reduces a coercive force of a high-frequency magnetic field applied part of the disk. Accordingly, it is possible to perform high-density recording with a small narrow head.
However, it is known that a recording performance of the high-frequency oscillation element decreases with an increase of the length of application time of a drive voltage. The decrease in recording performance of the high-frequency oscillation element (element lifetime) over time has a considerable impact on the quality of the magnetic disk device.
It is an object of the embodiment of the present invention to provide a magnetic disk device capable of suppressing deterioration in quality due to a decrease in element lifetime and a method of controlling the magnetic disk device.
In general, according to one embodiment, a magnetic disk device includes: a magnetic disk; a head having a magnetic flux control unit configured to generate a magnetic field toward the magnetic disk; a control circuit configured to apply a drive voltage for generating a magnetic field to the magnetic flux control unit; and a controller configured to control the head and the control circuit, respectively. The controller determines whether or not to cause the magnetic flux control unit to generate a magnetic field, and in accordance with the determination result, causes the control circuit to apply a drive voltage to the magnetic flux control unit so that an assisted recording area and a non-assisted recording area are provided in the magnetic disk mixedly as desired. The assisted recording area is an area of the magnetic disk in which data is written while a magnetic field is generated and the non-assisted recording area is an area of the magnetic disk in which data is written while a magnetic field is not generated.
A magnetic disk device (hereinafter referred to as “HDD”) according to an embodiment will be described below with reference to
The HDA 2 includes a magnetic disk (hereinafter simply referred to as “disk”) 21, a spindle motor (hereinafter referred to as “SPM”) 22, an arm 23, and a voice coil motor (hereinafter referred to as “VCM”) 24.
The disk 21 is a magnetic recording medium having a recording surface on which data is magnetically recorded. In the example illustrated in
The arm 23 and the VCM 24 constitute an actuator. A head 25 is mounted on the arm 23. The VCM 24 is driven by an electric power supplied from the power source through the driver IC 3 and controls the arm 23 to move the head 25 to a target position on the disk 21. In the configuration example illustrated in
The substrate 211 is made of a disk-shaped non-magnetic material. The soft magnetic layer 212 is made of a material having soft magnetic characteristics and formed on the substrate 21. The magnetic recording layer 213 is formed on the soft magnetic layer 212 and has magnetic anisotropy in a direction perpendicular to a surface of the disk 21 (the surface of the magnetic recording layer 213 or the surface of the protective film layer 214). The protective film layer 214 is formed on the magnetic recording layer 213.
The head 25 includes a slider 251 which is a main body, and a read head RH and a write head WH both mounted on the slider 251. The read head RH reads data recorded on a data track on the disk 21. The write head WH writes data on the disk 21. The head 25 writes data on the disk 21 in units of blocks including at least one sector, and reads data from the disk 21 in units of blocks. The track is defined as a continuous area in the circumferential direction of the disk 21 and includes a plurality of sectors. One sector is defined as a segment of an area obtained by dividing the track into a plurality of parts in the circumferential direction, and is a minimum unit of read data or write data for the disk 21.
The slider 251 is made of, for example, a sintered body (AlTic) of alumina and titanium carbide. The slider 251 has a disk facing surface (air bearing surface (ABS)) 252 facing the surface of the disk 21 and a trailing end 253 located on an outflow side of the air flow direction A. Parts of the read head RH and the write head WH are exposed from a disk facing surface 252 and faces the surface of the disk 21.
The read head RH includes a magnetic film RH1, a shield film RH2, and a shield film RH3. The magnetic film RH1 is located between the shield film RH2 and the shield film RH3 and produces a magnetoresistance effect. The shield film RH2 is located on the trailing end 253 side with respect to the magnetic film RH1. The shield film RH3 is located opposite to the shield film RH2 with respect to the magnetic film RH1, and faces the shield film RH2 with the magnetic film RH1 interposed therebetween. Lower ends of the magnetic film RH1, the shield film RH2, and the shield film RH3 are exposed from a disk facing surface 252 and face the surface of the disk 21.
The write head WH is provided on the trailing end 253 side of the slider 251 with respect to the read head RH. The write head WH includes a main magnetic pole WH1, a trailing shield (write shield) WH2, an insulator WH3, a recording coil WH4, and a magnetic flux control unit WH5.
The main magnetic pole WH1 is made of a soft magnetic material having a high saturation magnetic flux density. The main magnetic pole WH1 generates a recording magnetic field perpendicular to the surface of the disk 21 in order to magnetize the magnetic recording layer 213 of the disk 21. In the example illustrated in
The write shield WH2 is made of a soft magnetic material having a high saturation magnetic flux density. The write shield WH2 is provided to efficiently close a magnetic path via the soft magnetic layer 212 right below the main magnetic pole WH1. The write shield WH2 is located on the trailing end 253 side with respect to the main magnetic pole WH1, and is connected to the main magnetic pole WH1 via the insulator WH3. The main magnetic pole WH1 and the write shield WH2 are electrically insulated and form a magnetic circuit. The write shield WH2 stands up to face the main magnetic pole WH1 and has a shape bent along the disk facing surface 252 (the surface of the disk 21). A distal end portion WH2a on the disk facing surface 252 side is opposed to the distal end portion WH1a of the main magnetic pole WH1 with a write gap formed therebetween. A lower surface of the distal end portion WH2a is exposed from the disk facing surface 252 and faces the surface of the disk 21.
The recording coil WH4 is provided so as to be wound around the magnetic circuit including the main magnetic pole WH1 and the write shield WH2 so that a magnetic flux flows through the main magnetic pole WH1. The recording coil WH4 is wound, for example, between the main magnetic pole WH1 and the write shield WH2. By supplying a current of a predetermined magnitude (hereinafter referred to as “recording current”) to the recording coil WH4, a recording magnetic field is excited in the main magnetic pole WH1 and the write shield WH2. As a result, the main magnetic pole WH1 and the write shield WH2 are magnetized. The magnetization direction of the recording bit of the magnetic recording layer 213 of the disk 21 is changed by the magnetic flux flowing through the magnetized main magnetic pole WH1 and the write shield WH2. Accordingly, a magnetization pattern corresponding to the recording current is recorded on the disk 21.
The magnetic flux control unit WH5 is a high-frequency oscillation element, for example, a spin torque oscillator (STO) (hereinafter referred to as “spin torque oscillator WH5”). The spin torque oscillator WH5 is provided between the distal end portion WH1a of the main magnetic pole WH1 and the distal end portion WH2a of the write shield WH2 (hereinafter referred to as “write gap”). The spin torque oscillator WH5 includes, for example, an underlayer made of a non-magnetic conductive layer, a spin injection layer, an intermediate layer, an oscillation layer, and a gap layer made of a nonmagnetic conductive layer laminated from the distal end portion WH1a side of the main magnetic pole WH1 to the distal end portion WH2a side of the write shield WH2 in the presented order.
In the spin torque oscillator WH5, when a drive voltage of a predetermined magnitude is applied, the magnetization is uniformly rotated by a gap magnetic field generated in the write gap (spin precession motion), and the high-frequency magnetic field (microwave) is generated toward the disk 21. The frequency of the microwave is sufficiently higher than the frequency of the recording signal. The spin torque oscillator WH5 reduces the coercive force of the magnetic recording layer 213 by applying a high-frequency magnetic field to the magnetic recording layer 213 of the disk 21. When the spin torque oscillator WH5 generates a large amount of spin precession motion, the permeability of the spin torque oscillator WH5 is as low as that of air. Therefore, the magnetic flux from the main magnetic pole WH1 flows more easily toward the disk 21 than toward the write gap (spin torque oscillator WH5). Accordingly, the spin torque oscillator WH5 assists in writing data to the disk 21. In contrast, when the spin precession motion is not generated in the spin torque oscillator WH5 or is generated by an amount less than usual, the permeability of the spin torque oscillator WH5 is higher than the permeability of air. Therefore, the magnetic flux from the main magnetic pole WH1 is more likely to flow toward the write gap (spin torque oscillator WH5) than toward the disk 21.
In the following description, a writing process in which a drive voltage is applied to the spin torque oscillator WH5 to write data on the disk 21 while a high-frequency magnetic field is generated is referred to as “assisted recording”. Further, the drive voltage when the assisted recording is executed is referred to as “assist voltage”. In the assisted recording, data can be written with a narrower track pitch, and the recording density can be increased, compared with a writing process in which data is written without applying an assist voltage to the spin torque oscillator WH5. In contrast to the assisted recording, a writing process in which data is written without applying an assist voltage to the spin torque oscillator WH5 and without generating a high-frequency magnetic field is referred to as “non-assisted recording”. Note that it is also possible to provide the assist voltage with a width. For example, it is also possible to execute the assisted recording by selecting and applying a drive voltage such as a maximum value of the assist voltage, or 70%, 50%, 30% or the like of the maximum value. In other words, the assisted recording may include an arbitrary writing process for writing data by applying an assist voltage within a predetermined range.
The head 25 having such a configuration is provided on each of the five arms 23a to 23e. Each head 25a to 25e is tested for its operating performance, for example, the element lifetime of the spin torque oscillator WH5, before being incorporated into the HDD 1. The operation performance of the head 25 (hereinafter referred to as “head lifetime”) is not uniform, and there is superiority or inferiority among, for example, the five heads 25a to 25e.
The driver IC 3 controls the driving of the SPM 22 and the VCM 24 (24a to 24e) according to the control of the system controller 8 (more specifically, MPU 81 described later).
The head amplifier IC (preamplifier) 4 includes a read amplifier and a write driver (not illustrated). The read amplifier amplifies the read signal read from the disk 21 and outputs it to the system controller 8 (specifically, a read/write (R/W) channel 85 described later). The write driver in the head amplifier IC (preamplifier) 4 is an element configured to output a recording current corresponding to write data output from an R/W channel 85 to the head 25, and includes, for example, a recording current control circuit 41 and an STO voltage control circuit 42.
The recording current control circuit 41 is electrically connected to the recording coil WH4 and supplies a recording current corresponding to the write data output from the R/W channel 85 to the recording coil WH4. For example, the recording current control circuit 41 supplies a recording current to the recording coil WH4 under the control of the system controller 8 (MPU 81).
The STO voltage control circuit 42 is electrically connected to the spin torque oscillator WH5, and applies a predetermined assist voltage to the spin torque oscillator WH5 under the control of the system controller 8 (MPU 81), for example. In other words, the STO voltage control circuit 42 is a control circuit configured to apply a drive voltage (assist voltage) that generates a high-frequency magnetic field to the spin torque oscillator WH5, which is a magnetic flux control unit.
The buffer 5 is a semiconductor memory configured to temporarily record data transmitted and received between the HDD 1 and the host 9. Examples of the buffer 5 include Dynamic Random Access Memory (DRAM), Static Random Access Memory (SRAM), Synchronous Dynamic Random Access Memory (SDRAM), Ferroelectric Random Access Memory (FeRAM), and Magneto resistive Random Access Memory (MRAM).
The volatile memory 6 is a semiconductor memory in which the stored data is lost when power supply is cut off. The volatile memory 6 stores data necessary for processing in each unit of the HDD 1. The volatile memory 6 is, for example, DRAM or SDRAM.
The non-volatile memory 7 is a semiconductor memory in which the stored data is recorded even when power supply is cut off. Examples of the non-volatile memory 7 include an NOR type and NAND type flash ROM (Flash Read Only Memory: FROM). In the storage area of the non-volatile memory 7, an initial program loader (IPL) is stored in advance. The MPU 81 to be described later loads at least a part of a control program stored in the disk 21 to a control memory 84 to be described later by executing IPL when the power source is turned on, for example.
The system controller 8 is realized by using, for example, a large-scale integrated circuit (LSI) called a System-on-a-Chip (SoC) in which a plurality of elements are integrated on a single chip. The system controller 8 includes the MPU 81, a buffer control unit 82, a disk control unit 83, and a control memory 84, respectively. The system controller 8 is electrically connected to the driver IC 3, the head amplifier IC 4, the buffer 5, the volatile memory 6, the non-volatile memory 7, and the host 9.
The MPU 81 is a main controller configured to control each part of the HDD 1. When the power source is turned on, the MPU 81 executes the IPL of the non-volatile memory 7 and loads the control program stored in the disk 21 into the control memory 84. Accordingly, the MPU 81 executes a process for operating the system controller 8 in a predetermined operation mode. The MPU 81 is connected to the driver IC 3, the disk control unit 83 (specifically, the R/W channel 85 described later), and the control memory 84.
The MPU 81 includes a read/write (R/W) control unit 811 and a current/voltage control unit 812. The MPU 81 executes processing in the R/W control unit 811 and the current/voltage control unit 812 on the firmware. Note that the MPU 81 may include the R/W control unit 811 and the current/voltage control unit 812 as a circuit.
The R/W control unit 811 controls a data reading process and a data writing process in accordance with commands from the host 9. For example, the R/W control unit 811 controls a rotation speed of the SPM 22 via the driver IC 3 and also executes servo control for controlling the VCM 24 and positioning the head 25. During the data reading process, the R/W control unit 811 controls the data read operation from the disk 21 and controls the process of read data. At the time of data writing process, the R/W control unit 811 controls the data writing operation to the disk 21 and selects a storage destination of the write data transferred from the host 9.
In addition, the R/W control unit 811 determines assisted recording conditions described later. In determining the assisted recording conditions, the R/W control unit 811 detects the head lifetime of the head 25, for example, and compares the detected lifetime with a reference lifetime described later. The R/W control unit 811 also determines whether or not the write data storage destination is the media cache 21m. Then, in accordance with a determination result of the assisted recording conditions, the R/W control unit 811 executes control for writing the write data via the assisted recording or the non-assisted recording.
The current/voltage control unit 812 receives an instruction from the R/W control unit 811 and controls the current and the voltage supplied from the power source. For example, the current/voltage control unit 812 controls the head amplifier IC 4 (the recording current control circuit 41 and the STO voltage control circuit 42), and controls (adjusts) the recording current and the assist voltage for the head 25. Accordingly, in the write head WH, a recording current supplied from the recording current control circuit 41 to the recording coil WH4 is controlled. Further, an assist voltage applied from the STO voltage control circuit 42 to the spin torque oscillator WH5 is controlled.
The buffer control unit 82 controls data exchange between the buffer 5 and the system controller 8. The buffer control unit 82 is connected to the buffer 5 and the disk control unit 83.
The disk control unit 83 has a read/write (R/W) channel 85 and controls data transfer between the host 9 and the R/W channel 85 in accordance with an instruction from the MPU 81. The disk control unit 83 is connected to the buffer 5, the volatile memory 6, the non-volatile memory 7, the host 9, the MPU 81, and the buffer control unit 82.
The R/W channel 85 executes a signal process of read data and write data in response to an instruction from the MPU 81. The R/W channel 85 has a circuit or a function for measuring a signal quality of read data. For example, the R/W channel 85 has a function of executing error correction processing (Error Checking and Correcting: ECC) on read data read from the disk 21. The R/W channel 85 is connected to the head amplifier IC 4 and MPU 81.
The control memory 84 is a volatile memory such as a DRAM. A part of the control program is loaded into the storage area of the control memory 84. A part of the storage area of the control memory 84 is used as a command buffer. The command buffer stores a queue of read commands and write commands received from the host 9. The control memory 84 is connected to the MPU 81.
When reading and writing data from/to the disk 21, the system controller 8 operates as follows. When the read command is received from the host 9, the MPU 81 stores read data in the buffer 5 via the head amplifier IC 4, the disk control unit 83, and the buffer control unit 82. Then, the MPU 81 controls to transmit the read data stored in the buffer 5 to the host 9. Upon reception of a write command (write data) from the host 9, the system controller 8 stores the write data in the buffer 5 via the buffer control unit 82. The MPU 81 writes the write data to the disk 21 via the buffer control unit 82, the disk control unit 83, and the head amplifier IC 4.
In the embodiment, the system controller 8 appropriately switches the mode of control between control to execute the assisted recording and control not to execute the assisted recording when data is written to the disk 21. When executing the assisted recording, the MPU 81 applies an assist voltage to the spin torque oscillator WH5 to cause the write head WH to write data. In contrast, when the assisted recording is not executed and the non-assisted recording is executed, the MPU 81 causes the write head WH to write data without applying an assist voltage to the spin torque oscillator WH5.
Accordingly, an area where data is to be written via the assisted recording, that is, an area where the data is written in an assisted manner (hereinafter referred to as “MAMR function ON area”), and an area where data is written via the non-assisted recording, that is, an area where the data is written without assistance (hereinafter referred to as “MAMR function OFF area”) can be mixedly provided on the recording surface of one disk 21. Therefore, on each recording surface of the plurality of disks 21, the MAMR function ON area, which is the assisted recording area, and the MAMR function OFF area, which is the non-assisted recording area, can be mixedly provided.
In this manner, the system controller 8 can appropriately switch the mode of control between the control to execute the assisted recording and the control not to execute the assisted recording (non-assisted recording) when writing data to the disk 21, so that each recording surface of the plurality of disks 21 may be provided with only one of the MAMR function ON area and the MAMR function OFF area. In other word, a plurality of disks 21 may mixedly include the disk 21 having only the MAMR function ON area and the disk 21 having only the MAMR function OFF area.
Next, a data writing process for mixedly providing the MAMR function ON area and the MAMR function OFF area in this manner will be described with reference to a flowchart.
As illustrated in
If the assisted recording conditions are satisfied in S101, the write data is written via the assisted recording (S102). Therefore, the current/voltage control unit 812 receives an instruction from the R/W control unit 811 and controls the recording current control circuit 41 of the head amplifier IC 4 to apply a recording current to the recording coil WH4. The current/voltage control unit 812 controls the STO voltage control circuit 42 of the head amplifier IC 4 to apply an assist voltage to the spin torque oscillator WH5. Accordingly, the R/W control unit 811 causes the write head WH to write (assisted recording) the write data to the disk 21 in a state in which a high-frequency magnetic field (microwave) is applied from the spin torque oscillator WH5 to the disk 21.
In contrast, if the assisted recording conditions are not satisfied in S101, the data is written via the non-assisted recording (S103). Therefore, the current/voltage control unit 812 controls the recording current control circuit 41 of the head amplifier IC 4 to apply a recording current to the recording coil WH4. In contrast, the current/voltage control unit 812 does not execute the control to apply an assist voltage to the spin torque oscillator WH5. Accordingly, the R/W control unit 811 causes the write head WH to write (non-assisted recording) the write data to the disk 21 in a state in which a high-frequency magnetic field (microwave) is not applied from the spin torque oscillator WH5 to the disk 21.
In this manner, if the assisted recording conditions are satisfied, the assisted recording is executed, and the MAMR function ON area is generated on the recording surface of the disk 21. In contrast, if the assisted recording conditions are not satisfied, non-assisted recording is executed, and the MAMR function OFF area is generated on the recording surface of the disk 21.
The specific contents (determination factors) of the assisted recording conditions can be applied as desired. For example, the ratio of the MAMR function ON area and the MAMR function OFF area on the recording surface of the disk 21 may be set in advance according to the head lifetime of the head 25, and the success or failure of the assisted recording conditions may be determined based on the ratio. As an example, the ratio of the MAMR function OFF area may be increased with a decrease in the head lifetime of the head 25. Accordingly, since the head 25 having a shorter head lifetime has a smaller MAMR function OFF area, the application time of the assist voltage to the spin torque oscillator WH5 can be reduced, and thus the actual head lifetime can be extended compared to the test. As a result, the lifetime of the entire head 25, that is, the HDD 1 itself (device lifetime) can be extended to the lifetime equivalent to that of the head 25 having the longest head lifetime.
For example, in the configuration example illustrated in
Further, for example, according to the configuration example illustrated in
Next, the R/W control unit 811 compares the detected head lifetime of each head 25 with a predetermined threshold value (hereinafter referred to as “reference lifetime”) (S202). The reference lifetime is, for example, an appropriate value of the head lifetime that is assumed when the head 25 reads read data and writes write data while appropriately switching the mode between the assisted recording and the non-assisted recording.
As a result of the comparison, for example, when the detected head lifetime has not reached the reference lifetime, the R/W control unit 811 determines that the assisted recording conditions are satisfied for the head 25 whose head lifetime has not reached the reference lifetime. In this case, the R/W control unit 811 sets the ratio of the MAMR function ON area that is written via the assisted recording by the head 25 (in other words, the ratio of the MAMR function OFF area) in accordance with the head lifetime (S203). For example, in the configuration example illustrated in
When the ratio of the MAMR function ON area is set, the R/W control unit 811 executes the assisted recording with the head 25 (S204). When the assisted recording is executed, an assist voltage is applied from the STO voltage control circuit 42 to the spin torque oscillator WH5. Accordingly, the R/W control unit 811 causes the write head WH to write the write data to the disk 21 in a state in which a high-frequency magnetic field (microwave) is applied from the spin torque oscillator WH5 to the disk 21.
In contrast, when the detected head lifetime has reached the reference lifetime, the R/W control unit 811 determines that the assisted recording conditions are not satisfied for the head 25 whose head lifetime has reached the reference lifetime. In this case, the head 25 executes the non-assisted recording (S205). When the non-assisted recording is executed, no assist voltage is applied from the STO voltage control circuit 42 to the spin torque oscillator WH5. Accordingly, the R/W control unit 811 causes the write head WH to write the write data to the disk 21 without applying a high-frequency magnetic field (microwave) to the disk 21 from the spin torque oscillator WH5.
When the assisted recording conditions are determined in accordance with the head lifetime in this manner, for example, in the configuration example illustrated in
In the embodiment, a media cache 21m is allocated to the recording surface of the disk 21. A data writing process is frequently executed on the media cache 21m. Therefore, whether or not the assisted recording conditions are satisfied may be determined based on whether or not it is the media cache 21m.
Note that if the storage destination of the write data is not the media cache 21m, the R/W control unit 811 may determine that the assisted recording conditions are satisfied, or may continue to determine other assisted recording conditions. For example, when it is determined that the assisted recording conditions are satisfied, the write data is written via the assisted recording in the recording area 21s other than the media cache 21m. When other assisted recording conditions are determined, the R/W control unit 811 causes the write data to be written via the assisted recording or via the non-assisted recording in accordance with the determination result. In this case, for example, the first determination process described above may be performed, and the write data may be written via the assisted recording or via the non-assisted recording in accordance with the head lifetime.
As described above, according to the embodiment, when data is written to the disk 21, it is possible to appropriately switch the mode of control between the control to execute the assisted recording and the control not to execute the assisted recording (non-assisted recording). Such switching may be performed by determining the assisted recording conditions for each zone in which the head 25 writes data (hereinafter referred to as “head zone”). The head zone is a recording area including one or a plurality of tracks. At that time, for example, based on the write amount (writing amount) for each head zone, the head zone in the MAMR function ON area may be replaced with the head zone in the MAMR function OFF area between different disks 21 or may be moved within the same disk 21.
These replacement of the head zone (hereinafter referred to as “zone replacement”) and movement (hereinafter referred to as “zone movement”) are executed by updating information in the address table of the disk 21.
Next, the R/W control unit 811 selects a head zone with the largest write amount based on the detected write amount via the assisted recording for each head zone (S402). The selected head zone is subjected to the zone replacement or the zone movement.
Subsequently, the R/W control unit 811 determines a write amount condition based on the write amount via the assisted recording in the selected head zone (S403). The write amount condition is a determination condition as to whether or not the write amount in assisted recording in the head zone is equal to or greater than a predetermined threshold value (hereinafter referred to as “reference write amount”). In determining the write amount condition, the R/W control unit 811 compares the write amount via the assisted recording of the selected head zone with the reference write amount. The reference write amount is, for example, the write amount of write data that is assumed to deteriorate the head lifetime if the write data is continuously written via the assisted recording.
For example, when the detected write amount is less than the reference write amount as a result of the comparison, the R/W control unit 811 detects the write amount achieved by the head 25 for each head zone (S401) again and selects a head zone with the largest write amount (S402), and then repeats a series of control for determining the write amount conditions.
In contrast, when the detected write amount is equal to or greater than the reference write amount for example, the R/W control unit 811 determines the presence or absence of a head zone (unused area) in which data is not written (S404). In the determination, the R/W control unit 811 determines, for example, the presence or absence of a head zone in which no logical address is allocated in the record of the disk 21 (head 25) corresponding to the selected head zone in the address table. The R/W control unit 811 executes the zone replacement when there is no unused area and the zone movement when there is an unused area, respectively, as follows. However, it is not excluded that the zone replacement is performed when there is an unused area.
When there is no unused area, the R/W control unit 811 performs the zone replacement for a head zone (hereinafter referred to as “replacement source zone”) in which the write amount via the assisted recording is equal to or greater than the reference write amount (has reached the reference write amount) (S405). For example, the R/W control unit 811 selects a head zone in which the write amount of data recorded by each head 25 in non-assisted manner performs the non-assisted recording within a predetermined time is the smallest (hereinafter referred to as “replacement destination zone”). Then, the replacement source zone is replaced with the MAMR function OFF area, and the selected replacement destination zone is replaced with the MAMR function ON area. Specifically, the R/W control unit 811 replaces the logical address of the replacement source zone and the logical address of the replacement destination zone in the address table, and updates the table information. Accordingly, the logical address allocated to the physical address of the replacement source zone is updated to the logical address allocated to the physical address of the replacement destination zone. In addition, the logical address allocated to the physical address of the replacement destination zone is updated to the logical address allocated to the physical address of the replacement source zone. Therefore, the write data of the replacement source zone is moved from the MAMR function ON area to the MAMR function OFF area on the logical address. Also, the write data of the replacement destination zone is moved from the MAMR function OFF area to the MAMR function ON area on the logical address.
Therefore, in the address table after the zone replacement, as illustrated in
In contrast, as illustrated in
Note that, after detecting the write amount in S401, if the write amount of the head 25 gets closer to (is approaching) the head lifetime, the assisted recording conditions may be determined for each head zone of the disk 21 corresponding to the head 25. At this time, for example, based on the head lifetime, the head zone in the MAMR function ON area of the disk 21 may be replaced with or moved to the head zone in the MAMR function OFF area.
In addition, in the head 25 in which the write amount of the write data has approached the head lifetime, non-assisted recording may be executed and the write data may be written to the disk 21 in a mode with verification. Whether or not the write amount of the write data has approached the head lifetime is determined based on, for example, whether or not the write amount has reached the reference write amount. In the write mode with verification, after the data is written, the write data is read to confirm data contents. Accordingly, the situation where the write data is not properly written can be suppressed, and the reliability of the write data can be improved.
As described above, according to the HDD 1 of the embodiment, when data is written on the disk 21, it is possible to appropriately switch the mode of control between the control to execute the assisted recording and the control not to execute the assisted recording. Accordingly, the MAMR function ON area and the MAMR function OFF area can be mixedly provided on the recording surface of one disk 21. It is also possible to provide the MAMR function ON area and the MAMR function OFF area mixedly on each recording surface of a plurality of disks 21, or to use only one of the MAMR function ON area and the MAMR function OFF area.
When executing the assisted recording, the MPU 81 applies an assist voltage to the spin torque oscillator WH5 to cause the write head WH to write data. In contrast, when the assisted recording is not executed and the non-assisted recording is executed, the MPU 81 causes the write head WH to write data without applying an assist voltage to the spin torque oscillator WH5. Therefore, by appropriately switching control from the control to execute the assisted recording to the control not to execute the assisted recording, it is possible to reduce the application time of the assist voltage to the spin torque oscillator WH5. For this reason, the element lifetime of the spin torque oscillator WH5 can be improved, and deterioration in quality due to the decrease in element lifetime can be suppressed. Accordingly, the quality of the HDD 1 as a device can be maintained for a long time. Accordingly, for example, the degree of freedom of giving priority to the disk capacity of the HDD 1 or the lifetime of the apparatus is increased, and it becomes easier to meet the needs of various customers.
While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
Number | Date | Country | Kind |
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2019-161450 | Sep 2019 | JP | national |