Magnetic disk device

Abstract

To provide a magnetic disk device with high write performance.SOLUTION: A controller of a magnetic disk device calculates a first amount of power, which is the amount of power required for an unloading operation of the magnetic head, based on a state of a VCM when the VCM is in operation. The controller calculates a first set value based on the first amount of power. The controller performs a first write operation for writing a part of or all of second data to the magnetic disk when the amount of second data, which is first data stored in the volatile memory and not yet written to the magnetic disk, exceeds the first set value. The controller performs the unloading operation and saves the second data in the nonvolatile memory by using the power generated by the back electromotive force of a second motor when an external power supply is interrupted.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, in a magnetic disk device, user data received from a host is temporarily stored in a volatile memory, and then the user data stored in the volatile memory is written to a magnetic disk.

[0003] Also, magnetic disk devices capable of executing a power loss protection (PLP) operation are known. In the PLP operation, when a power loss occurs, user data in a volatile memory that has not yet been written to a magnetic disk is saved to a non-volatile memory by backup power. This prevents user data in a volatile memory that has not yet been written to a magnetic disk from being lost from the magnetic disk device. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2017 / 0024297 [Patent Document 2] U.S. Patent No. 9,111,583 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of one embodiment is to provide a magnetic disk drive with high write performance. [Means for solving the problem]

[0006] According to one embodiment, a magnetic disk device includes a magnetic disk, a magnetic head, a first motor, a second motor, a non-volatile memory, a volatile memory, and a controller. The magnetic head performs writing and reading on the magnetic disk. The first motor moves the magnetic head relative to the magnetic disk in a radial direction. The second motor rotates the magnetic disk. The volatile memory stores first data, which is data received from a host device, at least until the first data is written to the magnetic disk. The controller calculates a first amount of power, which is an amount of power required for an unload operation of the magnetic head, based on a first state of the first motor when the first motor is operating. The controller calculates a first setting value based on the first amount of power. The controller executes a first write operation to write a part or all of the second data to the magnetic disk in response to an amount of second data, which is the first data stored in the volatile memory and not yet written to the magnetic disk, exceeding the first setting value. When the external power supply is interrupted, the controller executes an unloading operation and saves the second data in the non-volatile memory using power generated by the back electromotive force of the second motor. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a block diagram showing an example of the configuration of a disk device according to the first embodiment. [Diagram 2] FIG. 2 is a diagram illustrating an example of the configuration of a magnetic disk according to the first embodiment. [Diagram 3] FIG. 3 is a diagram showing an example of a plurality of areas formed on the recording surface of the magnetic disk according to the embodiment. [Figure 4] FIG. 4 is a diagram illustrating an example of a transition of the amount of write data stored in the write buffer area according to the first embodiment. [Diagram 5] FIG. 5 is a diagram illustrating an example of a more detailed configuration of the cache management unit according to the first embodiment. [Figure 6] FIG. 6 is a flowchart illustrating an example of the operation of the cache management unit according to the first embodiment. [Figure 7] FIG. 7 is a flowchart illustrating an example of an operation in response to a write command according to the first embodiment. [Figure 8] FIG. 8 is a flowchart illustrating an example of control of the second write operation according to the first embodiment. [Figure 9] FIG. 9 is a flowchart illustrating an example of an operation when a power loss occurs according to the first embodiment. [Figure 10] FIG. 10 is a diagram illustrating an example of the configuration of a magnetic disk device according to the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, a magnetic disk device according to an embodiment will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments.

[0009] (First embodiment) 1 is a block diagram showing an example of the configuration of a disk device according to the first embodiment. A magnetic disk device 100 is connectable to a host device 200. The magnetic disk device 100 functions as an external storage device for the host device 200. The magnetic disk device 100 is connected to an external power supply 300. The magnetic disk device 100 operates using power supplied from the power supply 300.

[0010] The magnetic disk device 100 includes a magnetic disk 1, a spindle motor (SPM) 2, a magnetic head MH, an actuator arm AA, a voice coil motor (VCM) 3, a power supply circuit 5, a hard disk control circuit 6, a RAM (Random Access Memory) 7, a FROM (Flash read Only Memory) 8, a servo control circuit 9, a head control circuit 10, and a read / write channel 11.

[0011] The magnetic disk device 100 receives an access command from the host device 200. The magnetic disk device 100 writes data to the magnetic disk 1 or reads data from the magnetic disk 1 in response to the received access command.

[0012] The access command includes a logical address. The magnetic disk device 100 provides a logical address space to the host device 200. The logical address indicates a location in the address space. The host device 200 uses the logical address to specify a location to write data to or a location to read data from. The logical address is expressed as an LBA (Logical Block Address).

[0013] A magnetic layer capable of recording various types of information is provided on the surface of the magnetic disk 1. The magnetic disk device 100 may include one magnetic disk 1, or may include multiple magnetic disks 1 arranged coaxially. For ease of explanation, only one magnetic disk 1 is shown in FIG. 1.

[0014] 2 is a diagram showing an example of the configuration of the magnetic disk 1 of the first embodiment. Servo data used for positioning the magnetic head MH is written in a magnetic layer formed on the surface of the magnetic disk 1 by, for example, a servo writer or by self-servo writing (SSW).

[0015] 2 shows servo areas 15 arranged radially as an example of the arrangement of servo areas in which servo data is written. In the circumferential direction, a data area 16 in which data can be written is provided between two servo areas 15. A plurality of concentric tracks 17 are provided in the radial direction of the magnetic disk 1. A plurality of sectors are provided on the tracks 17 in the data area 16, in which data of a predetermined size is written. The predetermined size is the sector size.

[0016] The servo data includes servo marks, gray codes, burst patterns, and post codes. When writing data to the magnetic disk 1 or reading data from the magnetic disk 1, the positioning of the magnetic head MH, that is, the seek control and tracking control, is performed based on the servo data read by the magnetic head MH from the servo area 15.

[0017] The recording surface of the magnetic disk 1 is divided into at least two areas with different uses. One of the at least two areas is an LBA area, and the other of the at least two areas is a media cache area.

[0018] FIG. 3 is a diagram showing an example of a plurality of areas formed on the recording surface of the magnetic disk 1 according to the embodiment.

[0019] In the example shown in FIG. 3, an LBA area 120 is provided on the inner diameter side of the recording surface 110 of the magnetic disk 1, and a media cache area 130 is provided on the outer diameter side.

[0020] LBAs are mapped to the LBA area 120. By using the LBAs, the host device 200 can specify a write destination location or a read destination location in the LBA area 120. The LBA area 120 is used as the final storage destination for user data received from the host device 200. Note that user data received from the host device 200, that is, user data for which writing is requested by a write command, is referred to as write data.

[0021] The media cache area 130 is used as a temporary storage location for write data.

[0022] The number and positions of the media cache areas 130 provided on the recording surface 110 are not limited to the example shown in Fig. 3. Furthermore, the number and positions of the LBA areas 120 provided on the recording surface 110 are not limited to the example shown in Fig. 3. In addition to the LBA areas 120 and the media cache areas 130, the recording surface 110 may be provided with areas for any purpose.

[0023] Let us return to Figure 1. Data is written to and read from the magnetic disk 1 via a magnetic head MH. The magnetic head MH is provided at one end of an actuator arm AA, and writes and reads data to the magnetic disk 1. The magnetic head MH has a write head WH that writes data to the magnetic disk 1, and a read head RH that reads data from the magnetic disk 1. The magnetic head MH is supported on a slider SL.

[0024] The SPM 2 rotates the magnetic disk 1. The magnetic head MH moves relative to the surface of the magnetic disk 1 in the circumferential direction while maintaining a state in which it is slightly lifted above the surface of the magnetic disk 1 due to lift generated by the rotation of the magnetic disk 1.

[0025] The VCM 3 is provided at the end of the actuator arm AA opposite to the end where the magnetic head MH is provided. The VCM 3 drives and rotates the actuator arm AA about an axis 4. In this way, the VCM 3 moves the magnetic head MH relative to the magnetic disk 1 in the radial direction.

[0026] When the magnetic disk 1 is stopped rotating, the VCM 3 moves the magnetic head MH to a ramp mechanism (not shown). The ramp mechanism is provided at a position separated from the magnetic disk 1 and is configured to be able to hold the magnetic head MH. The operation of moving the magnetic head MH from above the magnetic disk 1 to the ramp mechanism is referred to as an unload operation.

[0027] The head control circuit 10 writes data to the magnetic disk 1 by sending a write signal corresponding to data input from a read / write channel 11 to the write head WH. The head control circuit 10 also amplifies the read signal output from the read head RH and supplies it to the read / write channel 11.

[0028] The read / write channel 11 code-modulates the write data stored in the write buffer area 71, and outputs the code-modulated write data to the head control circuit 10. The read / write channel 11 also code-demodulates the data transmitted from the head control circuit 10, and outputs the code-demodulated data to the read buffer area 72.

[0029] The RAM 7 is a volatile memory capable of high speed operation. A write buffer area 71 and a read buffer area 72 are allocated to the RAM 7.

[0030] The write buffer area 71 is an area in which write data received from the host device 200 is stored at least until the write data is written to the magnetic disk 1. The write data received from the host device 200 is temporarily stored in the write buffer area 71, and then written from the write buffer area 71 to the magnetic disk 1.

[0031] The read buffer area 72 is an area in which user data that is requested to be read by a read command and that is read from the magnetic disk 1 is temporarily stored. The data that is read from the magnetic disk 1 is stored in the read buffer area 72, and then the data is transferred from the read buffer area 72 to the host device 200.

[0032] In addition to the write buffer area 71 and the read buffer area 72, the RAM 7 may also include areas into which various data or programs used by the hard disk control circuit 6 and the like are loaded.

[0033] The FROM 8 is a non-volatile memory that stores various data or programs used by the hard disk control circuit 6 and the like. A PLP save area 81 is further allocated to the FROM 8. Write data in the write buffer area 71 is saved to the PLP save area 81 by a PLP operation.

[0034] The PLP operation is an operation in which, when a power loss occurs, the write data stored in the write buffer area 71 that has not yet been stored on the magnetic disk 1 is saved to a non-volatile memory. The PLP operation prevents the write data that has not yet been written to the magnetic disk 1 from being lost from the magnetic disk device 100. Therefore, the write data received in the write buffer area 71 is protected from being lost from the magnetic disk device 100.

[0035] The power loss refers to an unauthorized interruption of the supply of power from the power source 300. The power loss may also include an interruption of the supply of power from the power source 300 according to a normal sequence.

[0036] The servo control circuit 9 includes an SPM control unit 91 , a VCM control unit 92 , an SPM power generation control unit 93 , an SPM voltage / current monitoring unit 94 , and a VCM voltage / current monitoring unit 95 .

[0037] The SPM control unit 91 controls the rotation of the SPM2. The SPM voltage / current monitoring unit 94 monitors the voltage and current values ​​of the power supplied to the SPM2. The SPM voltage / current monitoring unit 94 has a circuit that measures the voltage and current values ​​of the power supplied to the SPM2, and repeatedly measures the voltage and current values ​​using this circuit. The SPM control unit 91 can use the voltage and current values ​​acquired by the SPM voltage / current monitoring unit 94 to control the rotation of the SPM2.

[0038] The VCM control unit 92 controls the rotation of the VCM3. The VCM voltage / current monitoring unit 95 monitors the voltage and current values ​​of the power supplied to the VCM3. The VCM voltage / current monitoring unit 95 includes a circuit that measures the voltage and current values ​​of the power supplied to the VCM3, and repeatedly measures the voltage and current values ​​using the circuit. The VCM control unit 92 can use the voltage and current values ​​acquired by the VCM voltage / current monitoring unit 95 to control the rotation of the VCM3.

[0039] The SPM power generation control unit 93 generates power using the back electromotive force generated in the SPM 2 when a power loss occurs. When a power loss occurs, the hard disk control circuit 6 starts the PLP operation. In the PLP operation, since power from the power supply 300 cannot be used, the back electromotive force generated by the SPM 2 continuing to rotate due to inertia is used. The SPM power generation control unit 93 supplies the back electromotive force generated in the SPM 2 to each circuit of the magnetic disk device 100 via the power supply switch 52 provided in the power supply circuit 5.

[0040] The power supply circuit 5 supplies power to each circuit of the magnetic disk device 100. The power supply circuit 5 includes a power loss detection unit 51 and a power supply switch 52.

[0041] The power loss detection unit 51 detects power loss. For example, the power loss detection unit 51 monitors the voltage of a power supply line for receiving power from the power source 300. When the voltage value of the power supply line is greater than a predetermined threshold value, it determines that no power loss has occurred. When the voltage value of the power supply line becomes smaller than the threshold value, the power loss detection unit 51 determines that a power loss has occurred. A value slightly smaller than the voltage value required for the magnetic disk device 100 to operate normally is used as the threshold value. Note that the method of detecting power loss by the power loss detection unit 51 is not limited to this.

[0042] The power supply switch 52 switches the power supply source for driving each circuit of the magnetic disk device 100. During a period in which no power loss is detected by the power loss detection unit 51, the power supply switch 52 supplies the power supplied from the power source 300 to each circuit of the magnetic disk device 100. In response to the detection of power loss by the power loss detection unit 51, the power supply switch 52 supplies the power generated by the SPM power generation control unit 93 using the back electromotive force of the SPM 2 to each circuit of the magnetic disk device 100.

[0043] The hard disk control circuit 6 includes an access control unit 61 and a buffer management unit 62. The hard disk control circuit 6 is an example of a controller.

[0044] The access control unit 61 interprets an access command received from the host device 200. Furthermore, the access control unit 61 controls data transfer between the magnetic disk 1 and each of the buffer areas 71, 72, and data transfer between each of the buffer areas 71, 72 and the host device 200, based on the access command.

[0045] When a write command is received from the host device 200, the access control unit 61 stores the write data requested to be written by the write command in the write buffer area 71. When the storage of the write data in the write buffer area 71 is completed, the access control unit 61 notifies the host device 200 of the completion of execution of the write command. The completion of execution of the write command can be notified before the write data is stored in the LBA area 120. This improves the transfer rate of the write data from the host device 200 to the magnetic disk device 100, i.e., the write performance.

[0046] In the first embodiment, in order to maximize the write performance, the capacity of the write buffer area 71 is set to be relatively large.

[0047] The access control unit 61 executes command reordering when writing the write data in the write buffer area 71 to the magnetic disk 1. Command reordering is an operation for determining the order of writing the plurality of write data in the write buffer area 71 so that the writing of the plurality of write data can be completed as quickly as possible when writing the plurality of write data to the magnetic disk 1. Therefore, the order of writing the plurality of write data to the magnetic disk 1 may differ from the order of receiving the corresponding plurality of write commands.

[0048] The capacity of the write buffer area 71 is set to be relatively large, thereby improving the efficiency of command reordering.

[0049] Thus, while the capacity of the write buffer area 71 is set to be relatively large, the amount of data that can be saved to the PLP save area 81 by the PLP operation is limited in various ways. As described above, the PLP operation is executed by utilizing the back electromotive force generated in the SPM2. Since power generation by the back electromotive force can be maintained only while the SPM2 is rotating by inertia, the upper limit of the amount of data that can be saved from the write buffer area 71 to the PLP save area 81 depends on the amount of power generated by the back electromotive force, etc. Therefore, it is impossible to save all of the write data stored in the write buffer area 71 to the PLP save area 81 without any omissions.

[0050] Therefore, the access control unit 61 copies the write data stored in the write buffer area 71 to the media cache area 130 at appropriate times. Of the write data stored in the write buffer area 71, the original write data, a copy of which has been written to the media cache area 130, is lost from the write buffer area 71 when a power loss occurs. After the power supply from the power supply 300 is resumed, write data that is the same as the original write data is restored in the write buffer area 71 based on the copy stored in the media cache area 130.

[0051] Of the write data stored in the write buffer area 71, all write data that has not yet been copied to the media cache area 130 is evacuated to the PLP evacuation area 81 in response to power loss. Therefore, the amount of write data stored in the write buffer area 71 that has not yet been copied to the media cache area 130 is controlled so as not to exceed the PLP setting value as much as possible. The PLP setting value corresponds to the upper limit amount of data that can be evacuated to the PLP evacuation area 81, and it is guaranteed that all user data up to the amount of the PLP setting value can be evacuated to the PLP evacuation area 81.

[0052] Hereinafter, write data that has been received from the host device 200 but has not yet been written to the LBA area 120 will be referred to as temporarily stored data. The temporarily stored data includes the write data stored in the write buffer area 71, a copy of the write data stored in the media cache area 130, and the write data saved in the PLP save area 81.

[0053] Furthermore, of the write data in the write buffer area 71, the write data whose copy has not yet been written to the media cache area 130 is referred to as unprotected temporarily stored data.

[0054] Furthermore, the copy of the write data written to each media cache area 130 is referred to as copy data.

[0055] Furthermore, the operation of copying the write data stored in the write buffer area 71 to the media cache area 130 is referred to as a first write operation. The operation of writing the write data stored in the write buffer area 71 to the LBA area 120 is referred to as a second write operation.

[0056] 4 is a diagram for explaining an example of the transition of the amount of write data stored in the write buffer area 71 according to the first embodiment. This diagram illustrates the timing of receiving a write command, the timing of executing the first write operation, the transition over time of the amount of unprotected temporarily stored data, the transition over time of the amount of write data in the write buffer area 71, and the transition over time of the amount of data transferred to the LBA area 120 by the second write operation.

[0057] The amount of write data in the write buffer area 71 is shown as percentage numerical information with the capacity of the write buffer area 71 taken as 100%. Also, the amount of unprotected temporarily stored data is shown as percentage numerical information with the PLP setting value taken as 100%.

[0058] 4, as a write command is received, write data is stored in the write buffer area 71, and this increases the amount of write data in the write buffer area 71. Also, the amount of unprotected temporarily stored data increases as a write command is received. Then, after the amount of unprotected temporarily stored data reaches the PLP setting value (timing t1), the first write operation is started.

[0059] In a period P1 before the timing t1 at which the first write operation is first performed, the magnetic disk device 100 continuously performs the second write operation. In a period after the timing t1, the first write operation is performed every time the amount of unprotected temporarily stored data reaches the PLP setting value. In a period in which the first write operation is not performed, that is, in the period P1 and each period P2 in FIG. 4, the second write operation is performed. Therefore, the amount of write data in the write buffer area 71 gradually decreases except for each timing at which the write data is stored in the write buffer area 71 in response to a write command.

[0060] The amount of data transferred to the LBA area 120 by the second write operation is maximum during period P1 and each period P2 in FIG. 4, and is zero at each timing when the first write operation is executed.

[0061] The amount of data transferred to the LBA area 120 by the second write operation can be considered as the transfer rate of the write data to the magnetic disk 1. Therefore, in the period after timing t1, line L1, which averages the amount of data transferred to the LBA area 120 by the second write operation, corresponds to the transfer rate of the write data to the magnetic disk 1. As is clear from line L1, in the period after timing t1, the first write operation is occasionally executed, causing the transfer rate of the write data to the magnetic disk 1 to deteriorate.

[0062] If the transfer rate of write data to the magnetic disk 1 deteriorates, the transfer rate of write data from the host device 200 to the magnetic disk device 100 (write performance, as referred to in this specification) may also deteriorate.

[0063] In the embodiment, in order to suppress as much as possible the deterioration of the transfer rate to the magnetic disk 1 caused by the execution of the first write operation, the execution frequency of the first write operation is reduced as much as possible. Specifically, the hard disk control circuit 6 reduces the execution frequency of the first write operation as much as possible by making the PLP setting value as large as possible. By reducing the execution frequency of the first write operation, the write performance is improved.

[0064] Here, a technique to be compared with the first embodiment will be described. The technique to be compared with the embodiment will be referred to as a comparative example. According to the comparative example, the PLP setting value is a fixed value. In the manufacturing process, a fixed value common to a large number of magnetic disk devices is set as the PLP setting value for each magnetic disk device. The worst value of the amount of data that can be saved by the PLP operation is estimated, and the PLP setting value is determined based on the estimated worst value. Then, the PLP setting value is set for a large number of magnetic disk devices.

[0065] The amount of power available for PLP operation may vary depending on the operating conditions of the magnetic disk drive (e.g., the motor temperature of the SPM or VCM). Therefore, the amount of data that can be saved by PLP operation may vary depending on the conditions. However, according to the comparative example, the PLP setting value is set based on the worst value of the amount of data that can be saved by PLP operation. Therefore, there is room to increase the amount of data that can be saved by PLP operation.

[0066] In contrast, according to the first embodiment, a buffer management unit 62 is provided that can dynamically change the PLP setting value. The buffer management unit 62 acquires the status of each of the motors 2, 3 while the magnetic disk device 100 is performing normal operation, and estimates the amount of power available for the PLP operation based on the acquired status. The buffer management unit 62 then determines the PLP setting value based on the estimated amount of power. This allows the PLP setting value to be larger than in the comparative example, and the frequency of execution of the first write operation to be reduced.

[0067] The method for determining the PLP setting value is described below.

[0068] When power loss occurs, an unload operation is executed before the start of the PLP operation in order to prevent the magnetic head MH from adhering to the magnetic disk 1. Therefore, the following formula (1) is established. P gSPM ≧P UL +P PLP (1)

[0069] P gSPM is the amount of power generated by the back electromotive force generated in SPM2. Hereafter, the amount of power generated by the back electromotive force generated in SPM2 is referred to as the SPM generated power amount. P UL is the power consumption during unloaded operation, or more precisely, the power consumed by VCM3 during unloaded operation. The power consumption during unloaded operation is denoted as unloaded power consumption. PLP is the amount of power used to save data by the PLP operation. The amount of power used to save data by the PLP operation is denoted as the PLP power amount.

[0070] By transforming equation (1), we obtain the following equation (2). P PLP ≦P gSPM -P UL (2)

[0071] As is clear from equation (2), the data evacuation by PLP operation requires a maximum of SPM power generation P gSPM Unloaded power consumption P UL The amount of power that can be used is calculated by subtracting the above.

[0072] PLP setting value C PLP is the amount of PLP power P PLP Therefore, the PLP setting value C PLP can be derived using the following equation (3). C PLP ≦C ref *(P PLP / P PLPref ) ··(3)

[0073] C ref is the reference value for the PLP setting. PLPref is the standard value of PLP power amount, C ref This is the amount of PLP power required to evacuate the write data.

[0074] Unloaded power consumption P UL depends on the coil temperature of VCM3. For example, in a situation where seeks occur continuously, the coil resistance of VCM3 increases due to heat generated by the coil of VCM3. As a result, the power consumption of VCM3 during unload operation, i.e., the unload power consumption P UL increases.

[0075] Power consumption P UL can be expressed by the following formula (4). In formula (4), R VCM is the coil resistance of VCM3. I VCM is the current flowing through VCM3.

number

[0076] As is clear from equation (4), the coil resistance R VCM Therefore, the hard disk control circuit 6 calculates the power consumption P UL Estimate. P ULest =P ULref *(R VCMest / R VCMref ) ··(5)

[0077] P ULest is the estimated unloaded power consumption. R VCMref is the standard value of the coil resistance of VCM3. ULref is the reference value of the unloaded power consumption. More specifically, the coil resistance of VCM3 is R VCMref is the unloaded power consumption when R VCMest is the estimated coil resistance of VCM3.

[0078] SPM power generation amount P gSPM can be calculated using the following equation (6).

number

[0079] I SPM is the induced current caused by the back electromotive force of SPM2. V EMF is the back electromotive force generated in SPM2. R SPM is the coil resistance of SPM2. R LOAD is the resistance of the load that consumes the back electromotive force of SPM2.

[0080] When the coil temperature of SPM2 rises, the coil resistance R SPM increases. The coil resistance R of SPM2 SPM When increases, the SPM power generation amount P gSPM Therefore, the hard disk control circuit 6 calculates the power generation amount P gSPMEstimate. P gSPMest =P gSPMref *(R SPMest / R SPMref ) ··(7)

[0081] P gSPMest is the estimated value of SPM power generation. R SPMest is the estimated coil resistance of SPM2. R SPMref is the standard value of the coil resistance of SPM2. gSPMref is the reference value of the SPM power generation amount. More precisely, the coil resistance of SPM2 is R SPMref is the amount of power generated by SPM when

[0082] The buffer management unit 62 shown in FIG. 1 determines the PLP setting value C PLP Set.

[0083] 5 is a diagram showing an example of a more detailed configuration of the buffer management unit 62 according to the first embodiment. In the example shown in this diagram, the buffer management unit 62 includes a VCM resistance estimator 63, an SPM resistance estimator 64, a first power amount estimator 65, a second power amount estimator 66, and a PLP setting value calculator 67.

[0084] The VCM resistance estimation unit 63 acquires the current value and voltage value of the power supplied to the VCM 3 measured by the VCM voltage / current monitoring unit 95. Then, the VCM resistance estimation unit 63 estimates the coil resistance R of the VCM 3 based on the current value and voltage value of the power supplied to the VCM 3. VCMest For example, the VCM resistance estimation unit 63 calculates an estimated value R of the coil resistance of the VCM 3 by dividing the acquired voltage value by the acquired current value. VCMest Get the.

[0085] The first power estimation unit 65 estimates the coil resistance R obtained by the VCM resistance estimation unit 63. VCMest Based on equation (5), the estimated value of the unloaded power consumption P ULest Calculate the standard value P ULref , RVCMref Each of these is set by the designer in advance. ULref , R VCMref Each of the above may be set to a common value among multiple magnetic disk devices 100, or may be set to a different value for each magnetic disk device 100.

[0086] The SPM resistance estimation unit 64 acquires the current and voltage values ​​of the power supplied to the SPM 2 measured by the SPM voltage / current monitoring unit 94. Then, the SPM resistance estimation unit 64 estimates the coil resistance R of the SPM 2 based on the current and voltage values ​​of the power supplied to the SPM 2. SPMest For example, the VCM resistance estimation unit 63 calculates an estimated value R of the coil resistance of the SPM 2 by dividing the acquired voltage value by the acquired current value. SPMest Get the.

[0087] The second power amount estimation unit 66 estimates the coil resistance R obtained by the SPM resistance estimation unit 64. SPMest Based on equation (7), the estimated value of the SPM power generation amount P gSPMest Calculate the reference value R SPMref , P gSPMref Each of these is set by the designer in advance. SPMref , P gSPMref Each of the above may be set to a common value among multiple magnetic disk devices 100, or may be set to a different value for each magnetic disk device 100.

[0088] The PLP setting value calculation unit 67 calculates the PLP setting value C PLP Calculate.

[0089] Specifically, the PLP setting value calculation unit 67 calculates the estimated value P ULest , Estimated amount of SPM power generation PgSPMest , and based on equation (2), the maximum amount of power available for PLP operation, P PLPmax The PLP setting value calculation unit 67 calculates the maximum value P PLPmax and the PLP setting value C based on equation (3). PLP The maximum value that can be set as CPLPmax Calculate the standard value P PLPref , C ref Each of these is set by the designer in advance. PLPref , C ref Each of the values ​​may be set to a common value for multiple magnetic disk devices 100, or may be set to a different value for each magnetic disk device 100. The PLP setting value calculation unit 67 calculates the maximum value C PLPmax Based on this, the PLP setting value C PLP The PLP setting value calculation unit 67 determines the maximum value C PLPmax PLP setting value C PLP or the maximum value C PLPmax The PLP setting value C is obtained by subtracting a certain margin from PLP may be obtained.

[0090] Next, the operation of the magnetic disk device 100 according to the first embodiment will be described.

[0091] FIG. 6 is a flowchart showing an example of the operation of the buffer management unit 62 according to the first embodiment.

[0092] The buffer management unit 62 determines whether or not the timing for updating the PLP setting value has arrived (S101). The method for determining the timing for updating the PLP setting value can be set by the designer. For example, the timing for updating the PLP setting value may be set to arrive at a predetermined time period. In another example, the timing for updating the PLP setting value may be set to arrive when a predetermined time has elapsed since the magnetic disk device 100 was started up.

[0093] Note that, before the first update timing, a predetermined initial value may be used as the PLP setting value. The initial value may be set by the same method as in the comparative example described above. Alternatively, the PLP setting value used before the previous operation was stopped may be used as the initial value.

[0094] The timing for updating the PLP setting value is set so that it occurs multiple times at different times after startup. Alternatively, the timing for updating the PLP setting value may be set so that it occurs only once after startup.

[0095] If the timing to update the PLP setting value has not arrived (S101: No), the process of S101 is executed again.

[0096] When the timing to update the PLP setting value has arrived (S101: Yes), the VCM resistance estimator 63 acquires the current value and voltage value of the power supplied to the VCM 3 from the VCM voltage / current monitor 95 (S102).

[0097] The VCM resistance estimation unit 63 obtains the current value and voltage value from the VCM voltage / current monitoring unit 95 while power is being supplied to the VCM 3, i.e., while the VCM 3 is operating. Specifically, the VCM resistance estimation unit 63 obtains the current value and voltage value from the VCM voltage / current monitoring unit 95 during a seek associated with access to the LBA area 120 or the media cache area 130. Alternatively, the VCM resistance estimation unit 63 may forcibly initiate a seek that does not involve access to the LBA area 120 or the media cache area 130 in order to obtain the current value and voltage value, and obtain the current value and voltage value from the VCM voltage / current monitoring unit 95 during the forcibly initiated seek.

[0098] The VCM resistance estimation unit 63 estimates the coil resistance value of the VCM 3 (more precisely, the estimated value R VCMest ) is calculated (S103).

[0099] The first power amount estimation unit 65 estimates the unloaded power consumption (more precisely, the estimated value P ULest ) is calculated (S104).

[0100] The SPM resistance estimation unit 64 acquires (S105) the current value and voltage value applied to the power supplied to the SPM 2 from the SPM voltage / current monitoring unit 94. The SPM resistance estimation unit 64 acquires the current value and voltage value from the SPM voltage / current monitoring unit 94 while power is being supplied to the SPM 2, i.e., while the SPM 2 is operating.

[0101] The SPM resistance estimation unit 64 estimates the coil resistance value of the SPM 2 (more precisely, the estimated value R SPMest ) is calculated (S106).

[0102] A second power amount estimation unit 66 estimates the SPM power generation amount (more precisely, the estimated value P gSPMest ) is calculated (S107).

[0103] The PLP setting value calculation unit 67 calculates a new PLP setting value based on the unloaded power consumption amount, the SPM generated power amount, formula (2), and formula (3) (S108). The new PLP setting value calculated in the process of S108 is used to control the first write operation until the process of S108 is executed next time.

[0104] FIG. 7 is a flowchart illustrating an example of an operation in response to a write command according to the first embodiment.

[0105] When the access control unit 61 receives a write command and write data (S201), the access control unit 61 stores the write data in the write buffer area 71 (S202). Then, the access control unit 61 notifies the host device 200 of the completion of execution of the write command in response to the completion of storing the write data in the write buffer area 71 (S203).

[0106] The access control unit 61 determines whether the amount of unprotected temporarily stored data in the write buffer area 71 exceeds the PLP setting value (S204).

[0107] If the amount of unprotected temporarily stored data in the write buffer area 71 exceeds the PLP setting value (S204: Yes), the access control unit 61 copies the unprotected temporarily stored data to the media cache area 130 (S205). The process of S205 corresponds to a first write operation.

[0108] In the process of S205, the access control unit 61 may copy the amount of unprotected temporarily stored data that exceeds the PLP setting value to the media cache area 130. Alternatively, the access control unit 61 may copy all of the unprotected temporarily stored data to the media cache area 130.

[0109] After the process of S205, or if the amount of unprotected temporarily stored data in the write buffer area 71 does not exceed the PLP set value (S204: No), the operation according to the write command ends.

[0110] FIG. 8 is a flowchart illustrating an example of control of the second write operation according to the first embodiment.

[0111] The access control unit 61 judges whether the magnetic disk device 100 is in an idle state (S301). The idle state is, for example, a state in which a period during which no access command has been received from the host device 200 exceeds a predetermined time.

[0112] If the magnetic disk device 100 is not in an idle state (S301: No), the access control unit 61 executes the process of S301 again.

[0113] When the magnetic disk device 100 is in an idle state (S301: Yes), the access control unit 61 selects write data related to one write command from the temporarily stored data in the write buffer area 71 (S302). The access control unit 61 selects the write data based on command reordering.

[0114] The access control unit 61 writes the selected write data to the LBA area 120 (S303). The process of S303 corresponds to a second write operation.

[0115] Following the process of S303, the access control unit 61 invalidates the write data that has been written to the LBA area 120 in the write buffer area 71 and the copy data of the write data in the media cache area 130 (S304). Then, the access control unit 61 executes the process of S301 again.

[0116] Invalidating write data means making the area in which the write data was stored available for use, or may mean erasing the write data.

[0117] 8, the second write operation is executed when the magnetic disk device 100 is in an idle state, but the trigger for the second write operation is not limited to this. The second write operation can be executed based on any trigger as long as it is executed during a period when the first write operation is not executed.

[0118] FIG. 9 is a flowchart illustrating an example of an operation when a power loss occurs according to the first embodiment.

[0119] When the power loss detection unit 51 detects the occurrence of a power loss (S401), the power source switch 52 switches the power supply source for each circuit from the power source 300 to the SPM power generation control unit 93 (S402).

[0120] In response to the detection of the occurrence of power loss, the hard disk control circuit 6 executes an unload operation (S403). Also, the access control unit 61 saves the unprotected temporarily stored data in the write buffer area 71 to the PLP save area 81 (S404).

[0121] The processes of S403 and S404 are executed using power generated by the back electromotive force of the SPM2.

[0122] When the process of S404 is completed, the magnetic disk device 100 stops operation (S405).

[0123] Thereafter, when power supply from the power source 300 to the magnetic disk device 100 is resumed (S406), the access control unit 61 transfers the temporarily stored data in the PLP save area 81 and the copy data in the media cache area 130 to the write buffer area 71 (S407). As a result, the temporarily stored data that was stored in the write buffer area 71 immediately before the power cut is restored to the write buffer area 71. Then, the operation at the time of the power loss is completed.

[0124] In the above description of the first embodiment, the hard disk control circuit 6 writes a part or all of the unprotected temporarily stored data to the media cache area 130 in the first write operation.

[0125] However, the media cache area 130 may be discarded from the magnetic disk 1, and the hard disk control circuit 6 may be configured to write a part or all of the unprotected temporarily stored data to the LBA area 120 in the first write operation. Even in such a configuration, the hard disk control circuit 6 calculates the PLP setting value by the series of operations shown in Fig. 6. In the PLP operation, the hard disk control circuit 6 saves the unprotected temporarily stored data to the PLP save area 81. When power supply is resumed, the hard disk control circuit 6 transfers the write data saved in the PLP save area 81 to the write buffer area 71.

[0126] Furthermore, the hard disk control circuit 6 estimated the amount of power generated by the SPM and the amount of unloaded power consumption, and calculated the PLP setting value based on these amounts obtained by estimation.

[0127] However, one of the SPM-generated power amount and the unloaded power consumption amount may be given as a set value by a designer. The hard disk control circuit 6 may be configured to estimate the other of the SPM-generated power amount and the unloaded power consumption amount.

[0128] As described above, according to the first embodiment, the hard disk control circuit 6 calculates the coil resistance value of the VCM3 based on the current value and voltage value of the power supplied to the VCM3 measured by the VCM voltage / current monitor 95 (see, for example, S103 in FIG. 6). The hard disk control circuit 6 calculates the unloaded power consumption based on the coil resistance value of the VCM3 (see, for example, S104 in FIG. 6). The hard disk control circuit 6 calculates the PLP setting value based on the unloaded power consumption (see, for example, S108 in FIG. 6). The hard disk control circuit 6 executes a first write operation to write a part or all of the unprotected temporarily stored data to the magnetic disk 1 in response to the amount of unprotected temporarily stored data exceeding the PLP setting value (see, for example, S204 and S205 in FIG. 7). When the external power supply is interrupted, the hard disk control circuit 6 uses power generated by the back electromotive force of the SPM 2 to perform an unload operation and save the unprotected temporarily stored data to the PLP save area 81 (see, for example, S402 to S404 in FIG. 9).

[0129] Therefore, the frequency of the first write operation is reduced, resulting in improved write performance.

[0130] Furthermore, according to the embodiment, the hard disk control circuit 6 calculates the PLP power amount, which is the amount of power that can be used for saving data by PLP operation out of the SPM power generation amount, based on the unloaded power consumption amount. The hard disk control circuit 6 calculates the PLP setting value based on the PLP power amount.

[0131] Therefore, the PLP setting value can be made larger than in the comparative example, and the frequency of the first write operation can be reduced.

[0132] Furthermore, according to the embodiment, the hard disk control circuit 6 calculates the coil resistance value of the SPM 2 based on the current value and voltage value of the power supplied to the SPM 2 measured by the SPM voltage / current monitoring unit 94 (see, for example, S105 and S106 in FIG. 6). The hard disk control circuit 6 calculates the SPM power generation amount based on the coil resistance value of the SPM 2.

[0133] Therefore, the PLP setting value can be made larger than in the comparative example, and the frequency of the first write operation can be reduced.

[0134] According to the embodiment, in the first write operation, the hard disk control circuit 6 copies a part or all of the unprotected temporarily stored data to the media cache area 130. The hard disk control circuit 6 executes a second write operation to write the write data stored in the write buffer area 71 to the LBA area 120 at least during the period when the first write operation is not being executed.

[0135] Also, according to an embodiment, when power supply from the power source 300 is resumed (see, for example, S406 in FIG. 9), the hard disk control circuit 6 transfers the copy written to the media cache area 130 and the write data saved in the PLP save area 81 to the write buffer area 71 (see, for example, S407 in FIG. 9).

[0136] Therefore, it is possible to increase the capacity of the write buffer area 71 while preventing write data that has not yet been written to the magnetic disk 1 from being lost from the magnetic disk device 100 due to power loss, thereby improving the write performance.

[0137] According to the embodiment, the hard disk control circuit 6 calculates the coil resistance value of the SPM 2 based on the current value and voltage value of the power supplied to the SPM 2 measured by the SPM voltage / current monitor 94 (see, for example, S105 and S106 in FIG. 6). The hard disk control circuit 6 calculates the SPM power generation amount based on the coil resistance value of the SPM 2 (see, for example, S107 in FIG. 6). The hard disk control circuit 6 calculates the PLP setting value based on the SPM power generation amount (see, for example, S108 in FIG. 6). The hard disk control circuit 6 executes a first write operation to write a part or all of the unprotected temporarily stored data to the magnetic disk 1 in response to the amount of unprotected temporarily stored data exceeding the PLP setting value (see, for example, S204 and S205 in FIG. 7). When the power supply from the outside is interrupted, the hard disk control circuit 6 executes the saving of the unprotected temporarily stored data to the PLP saving area 81 using the power generated by the back electromotive force of the SPM 2 (see, for example, S402 and S404 in FIG. 9).

[0138] Therefore, the frequency of the first write operation is reduced, resulting in improved write performance.

[0139] Furthermore, according to the embodiment, the PLP power amount, which is the amount of power that can be used for saving data by PLP operation out of the amount of SPM generated power, is calculated, and the PLP setting value is calculated based on the PLP power amount.

[0140] Therefore, the PLP setting value can be made larger than in the comparative example, and the frequency of the first write operation can be reduced.

[0141] Second Embodiment According to the first embodiment, the buffer management unit 62 calculates the coil resistance value of each of the motors 2, 3 based on the current value and voltage value of the power supplied to each of the motors 2, 3. The method of acquiring the coil resistance value of each of the motors 2, 3 is not limited to this.

[0142] In the second embodiment, another example of a method for acquiring the coil resistance value of each of the motors 2 and 3 will be described. In the following, matters different from the first embodiment will be described. Explanations of matters that are the same as those in the first embodiment will be omitted or will be described briefly.

[0143] 10 is a diagram showing an example of the configuration of a magnetic disk device 100a according to the second embodiment, in which the same components as those in the first embodiment are omitted.

[0144] The magnetic disk device 100 a includes a VCM temperature sensor 151 and an SPM temperature sensor 152 .

[0145] The VCM temperature sensor 151 is provided at a predetermined position inside the VCM 3 or in the vicinity of the VCM 3. The VCM temperature sensor 151 measures the coil temperature of the VCM 3.

[0146] The SPM temperature sensor 152 is provided at a predetermined position inside the SPM 2 or in the vicinity of the SPM 2. The SPM temperature sensor 152 measures the coil temperature of the SPM 2.

[0147] The hard disk control circuit 6 includes a buffer management unit 62a instead of the buffer management unit 62 of the first embodiment. The buffer management unit 62a includes a VCM resistance estimation unit 63a, an SPM resistance estimation unit 64a, a first power amount estimation unit 65, a second power amount estimation unit 66, and a PLP setting value calculation unit 67.

[0148] The VCM resistance estimation unit 63a estimates the coil resistance R of the VCM3 based on the coil temperature of the VCM3 measured by the VCM temperature sensor 151. VCMest Calculate.

[0149] The coil resistance of the VCM 3 depends on the coil temperature of the VCM 3. A correspondence relationship between the coil temperature of the VCM 3 and the coil resistance of the VCM 3 is set in advance in the magnetic disk device 100, and the VCM resistance estimation unit 63a estimates the coil resistance R of the VCM 3 based on the correspondence relationship. VCMestThe VCM resistance estimation unit 63a calculates the estimated coil resistance R of the VCM3 by adding a margin to the value determined based on the correspondence between the coil temperature of the VCM3 and the coil resistance of the VCM3. VCMest It is also possible to use the following.

[0150] The SPM resistance estimator 64a estimates the coil resistance R of the SPM 2 based on the coil temperature of the SPM 2 measured by the SPM temperature sensor 152. SPMest Calculate.

[0151] The coil resistance of the SPM 2 depends on the coil temperature of the SPM 2. A correspondence relationship between the coil temperature of the SPM 2 and the coil resistance of the SPM 2 is set in advance in the magnetic disk device 100, and the SPM resistance estimation unit 64a estimates the coil resistance R of the SPM 2 based on the correspondence relationship. SPMest Calculate.

[0152] The first power amount estimating unit 65, the second power amount estimating unit 66, and the PLP setting value calculating unit 67 execute the same processes as those in the first embodiment.

[0153] In this way, the hard disk control circuit 6 may calculate the coil resistance value of VCM3 based on the coil temperature of VCM3 measured by the VCM temperature sensor 151, and calculate the unloaded power consumption amount based on the coil resistance value of VCM3.

[0154] Furthermore, the hard disk control circuit 6 may calculate the coil resistance value of the SPM 2 based on the coil temperature of the SPM 2 measured by the SPM temperature sensor 152, and calculate the SPM generated power amount based on the coil resistance value of the SPM 2.

[0155] As described in the first and second embodiments, the hard disk control circuit 6 may calculate the unloaded power consumption based on the current value and voltage value of the power supplied to VCM3, or may calculate the unloaded power consumption based on the coil temperature of VCM3. In other words, the hard disk control circuit 6 calculates the unloaded power consumption based on the state of VCM3 when VCM3 is operating. The state of VCM3 when VCM3 is operating is the current value and voltage value of the power supplied to VCM3, or the coil temperature of VCM3.

[0156] As described in the first and second embodiments, the hard disk control circuit 6 may calculate the amount of power generated by the SPM based on the current and voltage values ​​of the power supplied to the SPM 2, or may calculate the amount of power generated by the SPM based on the coil temperature of the SPM 2. In other words, the hard disk control circuit 6 calculates the amount of power generated by the SPM based on the state of the SPM 2 when the SPM 2 is operating. The state of the SPM 2 when the SPM 2 is operating is the current and voltage values ​​of the power supplied to the SPM 2, or the coil temperature of the SPM 2.

[0157] Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. These embodiments and their modifications are included in the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. [Explanation of symbols]

[0158] 1 magnetic disk, 2 SPM, 3 VCM, 4 axis, 5 power supply circuit, 6 hard disk control circuit, 7 RAM, 8 FROM, 9 servo control circuit, 10 head control circuit, 11 read / write channel, 15 servo area, 16 data area, 17 track, 51 power loss detection unit, 52 power switch, 61 access control unit, 62, 62a buffer management unit, 63, 63a VCM resistance estimation unit, 64, 64a SPM resistance estimation unit, 65 first power amount estimation unit, 66 second power amount estimation unit, 67 PLP setting value calculation unit, 71 write buffer area, 72 read buffer area, 81 PLP evacuation area, 91 SPM control unit, 92 VCM control unit, 93 SPM power generation control unit, 94 SPM voltage / current monitoring unit, 95 VCM voltage / current monitoring unit, 100, 100a magnetic disk device, 110 recording surface, 120 LBA area, 130 Media cache area, 151 VCM temperature sensor, 152 SPM temperature sensor, 200 host device, 300 power supply, MH magnetic head.

Claims

1. A magnetic disk; a magnetic head for writing and reading data to and from the magnetic disk; a first motor for moving the magnetic head relative to the magnetic disk in a radial direction; a second motor for rotating the magnetic disk; A non-volatile memory; a volatile memory in which first data received from a host device is stored at least until the first data is written to the magnetic disk; calculating a first amount of power required for an unload operation of the magnetic head based on a first state of the first motor when the first motor is operating; calculating a first set value based on the first amount of power; execute a first write operation to write a part or all of the second data to the magnetic disk in response to an amount of the second data, which is the first data stored in the volatile memory and has not yet been written to the magnetic disk, exceeding the first set value; when the power supply from the outside is cut off, the unloading operation and the saving of the second data in the non-volatile memory are executed using power generated by the back electromotive force of the second motor. A controller; A magnetic disk device comprising:

2. a first measurement circuit for measuring a current value and a voltage value of power supplied to the first motor; the first state being the current value and the voltage value, respectively, measured by the first measurement circuit; The controller calculates a first resistance value, which is a coil resistance value of the first motor, based on the first state, and calculates the first amount of power based on the first resistance value.

2. The magnetic disk drive according to claim 1.

3. A first temperature sensor is further provided to measure a coil temperature of the first motor. the first condition is the coil temperature of the first motor measured by the first temperature sensor; The controller calculates a first resistance value, which is a coil resistance value of the first motor, based on the first state, and calculates the first amount of power based on the first resistance value.

2. The magnetic disk drive according to claim 1.

4. The controller: acquiring a second amount of power, which is an amount of power generated by a back electromotive force of the second motor, calculating a third amount of power, which is an amount of power usable for the evacuation, from the second amount of power based on the first amount of power, and calculating the first setting value based on the third amount of power; 2. The magnetic disk drive according to claim 1.

5. The controller: calculating the second amount of power based on a second state of the second motor when the second motor is operating; 5. The magnetic disk drive according to claim 4.

6. a second measurement circuit for measuring a current value and a voltage value of the power supplied to the second motor; the second state being the current value and the voltage value measured by the second measurement circuit, the controller calculates a second resistance value, which is a coil resistance value of the second motor, based on the second state, and calculates the second amount of power based on the second resistance value.

6. The magnetic disk drive according to claim 5.

7. A second temperature sensor is further provided to measure a coil temperature of the second motor. the second condition is the coil temperature of the second motor measured by the second temperature sensor; the controller calculates a second resistance value, which is a coil resistance value of the second motor, based on the second state, and calculates the second amount of power based on the second resistance value.

6. The magnetic disk drive according to claim 5.

8. A first area and a second area are allocated to the magnetic disk, to which logical addresses usable by the host device are mapped; the first write operation is an operation of copying a part or all of the second data to the second area, the controller executes a second write operation to write third data, which is the first data stored in the volatile memory, to the first area at least during a period in which the first write operation is not executed; 8. The magnetic disk drive according to claim 1.

9. When the external power supply is resumed, the controller transfers the second data written in the second area and the second data saved in the non-volatile memory to the volatile memory.

9. The magnetic disk drive according to claim 8.

10. A magnetic disk; a magnetic head for writing and reading data to and from the magnetic disk; a motor for rotating the magnetic disk; A non-volatile memory; a volatile memory in which first data received from a host device is stored at least until the first data is written to the magnetic disk; calculating a first resistance value, which is a coil resistance value of the motor, based on a state of the motor when the motor is operating; calculating a first amount of power, which is an amount of power generated by a back electromotive force of the motor, based on the first resistance value; calculating a first set value based on the first amount of power; execute a first write operation to write a part or all of the second data to the magnetic disk in response to an amount of the second data, which is the first data stored in the volatile memory and has not yet been written to the magnetic disk, exceeding the first set value; when the power supply from the outside is cut off, the second data is saved in the non-volatile memory using power generated by the back electromotive force of the motor. A controller; A magnetic disk device comprising:

11. A measurement circuit for measuring a current value and a voltage value applied to the power supplied to the motor is further provided. the states being the current values ​​and the voltage values ​​measured by the measurement circuitry, respectively; The magnetic disk drive according to claim 10.

12. A temperature sensor for measuring a coil temperature of the motor is further provided. The condition is the temperature of the coil measured by the temperature sensor. The magnetic disk drive according to claim 10.

13. The controller: calculating a second amount of power that is an amount of power that can be used for the evacuation out of the first amount of power, and calculating the first setting value based on the second amount of power; The magnetic disk drive according to claim 11.

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