Magnetic disk device and command reordering method thereof

A magnetic disk device comprising:

• a magnetic disk;
• a magnetic head;
• a voice coil motor configured to drive movement of the magnetic head relative to the magnetic disk;
• a drive circuit configured to drive the voice coil motor;
• a memory in which a seek time for a seek operation is stored in association with a seek distance of the magnetic head;
• and
• a controller configured to change the seek time stored in the memory in association with the seek distance based on a temperature of the voice coil motor and a power supply voltage of the drive circuit, the controller including an upper level processor and a lower level processor, and a buffer which holds a queue corresponding to write commands,
• wherein the upper level processor is configured to calculate the seek distance based on the write commands,
• wherein the lower level processor is configured to calculate a seek time correction value corresponding to the seek distance based on the temperature of the voice coil motor and the power supply voltage of the drive circuit,
• wherein the upper level processor causes the processor to execute reordering of the write commands held in the queue based on a seek time corrected according to the seek time correction value, and
• wherein the lower level processor causes the processor to execute a servo control at the time of data write in the magnetic disk based on a result of the reordering of the write commands.

A command reordering method of a magnetic disk device including a magnetic disk, a magnetic head, a voice coil motor which drives movement of the magnetic head relative to the magnetic disk, and a drive circuit which drives the voice coil motor, the method comprising:

• storing a seek time for a seek operation in association with a seek distance of the magnetic head;
• and
• changing the seek time stored in association with the seek distance based on a temperature of the voice coil motor and a power supply voltage of the drive circuit,
• wherein the seek time is changed by correcting a magnetic force and a coil resistance of the voice coil motor based on the temperature of the voice coil motor, and wherein the following relationships are satisfied:
• J1=JK*(DT−TM)+J2;
• R1=CK*(DT−TC)+R2;
• VS=J1/J2*IH*(R1+RS+RN+RH)*VM;
• and
• TH=TS*(sqrt(VS/VD2)−1), where
• the temperature of the voice coil motor is DT, a temperature-corrected magnetic force of the voice coil motor is J1, a reference magnetic force is J2, a magnetic reference temperature is TM, a magnetic temperature coefficient is JK, a temperature-corrected coil resistance of the voice coil motor is R1, a coil reference resistance is R2, a coil reference temperature is TC, a coil temperature coefficient is CK, a voltage required for the seek operation is VS, the maximum current required for the seek operation is IH, a resistance of a sense resistor which detects a seek current is RS, an on resistance of the drive circuit is RN, a resistance of a wiring from the drive circuit to the voice coil motor is RH, a voltage margin is VM, the power supply voltage of the drive circuit is VD, a seek time is TS, and a seek time correction value is TH.