Magnetic disk device and method
View Patent ↗According to one embodiment, a controller executes a first command for accessing a first recording surface, executes a seek operation subsequent to completion of the access according to the first command, and executes a second command for accessing a second recording surface subsequent to completion of the seek operation. The seek operation includes performing a waiting operation in accordance with a relative velocity in a radial direction between a first magnetic head and a second magnetic head after completion of the access according to the first command. The first magnetic head faces the first recording surface, and the second magnetic head faces the second recording surface. The seek operation includes executing, subsequent to the waiting operation, switching of a magnetic head in use from the first magnetic head to the second magnetic head and starting of movement of a group of the magnetic heads.
1 . A magnetic disk device comprising:
two or more magnetic disks including two or more recording surfaces;
a first motor configured to integrally rotate the two or more magnetic disks;
a group of magnetic heads facing mutually different recording surfaces among the two or more recording surfaces;
a second motor configured to integrally move the group of magnetic heads in a radial direction of the two or more magnetic disks; and
a controller configured to
execute a first command, the first command being a command for accessing a first recording surface among the two or more recording surfaces,
execute a seek operation for executing a second command subsequent to completion of access according to the first command, the second command being a command for accessing a second recording surface different from the first recording surface among the two or more recording surfaces, and
execute the second command subsequent to completion of the seek operation,
wherein the seek operation includes
performing a waiting operation in accordance with a relative velocity in the radial direction between a first magnetic head and a second magnetic head after the completion of the access according to the first command, the first magnetic head being a magnetic head facing the first recording surface in the group of magnetic heads, the second magnetic head being a magnetic head facing the second recording surface in the group of magnetic heads, and
executing, subsequent to the waiting operation, switching of a magnetic head in use from the first magnetic head to the second magnetic head and starting of movement of the group of magnetic heads using the second motor.
2 . The magnetic disk device according to claim 1 , wherein the controller is configured to
perform the waiting operation when an absolute value of the relative velocity is larger than a threshold, and
perform none of the waiting operation when the absolute value of the relative velocity is smaller than the threshold.
3 . The magnetic disk device according to claim 2 , wherein the waiting operation is an operation of waiting until the absolute value of the relative velocity becomes smaller than the threshold.
4 . The magnetic disk device according to claim 2 , wherein the controller is configured to calculate the threshold based on one or more of a seek distance, a combination of positions of the group of magnetic heads at a start and an end of the seek operation, a combination of the magnetic heads before and after the switching of the magnetic head in use, a temperature of the magnetic disk device, or a temperature of the second motor.
5 . The magnetic disk device according to claim 1 , wherein
the two or more recording surfaces are each provided with tracks, and
the controller is configured to calculate the relative velocity based on a relative position between a first track on the first recording surface and a second track on the second recording surface.
6 . The magnetic disk device according to claim 5 , wherein the controller is configured to
estimate an amount of eccentricity and an eccentric direction for each of the first track and the second track, and
calculate the relative position based on the amount of eccentricity and the eccentric direction of the first track and the amount of eccentricity and the eccentric direction of the second track.
7 . The magnetic disk device according to claim 6 , wherein the controller is configured to estimate the amount of eccentricity and the eccentric direction for each of the first track and the second track based on an amount of current supplied to the second motor, accelerations of the group of magnetic heads, or positions of the group of magnetic heads.
8 . The magnetic disk device according to claim 6 , wherein the controller is configured to
acquire, for each of the first track and the second track, information about an amount of current supplied to the second motor,
acquire information about positions of the group of magnetic heads based on the information about the amount of current supplied to the second motor and a coefficient, and
estimate the amount of eccentricity and the eccentric direction based on the positions of the group of magnetic heads.
9 . The magnetic disk device according to claim 6 , wherein the controller is configured to
acquire, for each of the first track and the second track, information about accelerations of the group of magnetic heads,
acquire information about positions of the group of magnetic heads based on the information about the accelerations of the group of magnetic heads and a coefficient, and
estimate the amount of eccentricity and the eccentric direction based on the information about the positions of the group of magnetic heads.
10 . The magnetic disk device according to claim 1 , further comprising a memory provided with a command queue in which one or more unexecuted commands are stored,
wherein the controller is configured to
calculate a time required for the waiting operation for each of the one or more unexecuted commands stored in the command queue, and
determine an execution order of the one or more unexecuted commands based on a calculated value of the time required for the waiting operation.
11 . A method of controlling a magnetic disk device, the magnetic disk device including two or more magnetic disks, a group of magnetic heads, and a motor, the two or more magnetic disks including two or more recording surfaces and being integrally rotated, the group of magnetic heads facing mutually different recording surfaces among the two or more recording surfaces, the motor integrally moving the group of magnetic heads in a radial direction of the two or more magnetic disks, the method comprising:
executing a first command, the first command being a command for accessing a first recording surface among the two or more recording surfaces;
executing a seek operation for executing a second command subsequent to completion of access according to the first command, the second command being a command for accessing a second recording surface different from the first recording surface among the two or more recording surfaces; and
executing the second command subsequent to completion of the seek operation,
wherein the seek operation includes
performing a waiting operation in accordance with a relative velocity in the radial direction between a first magnetic head and a second magnetic head after the completion of the access according to the first command, the first magnetic head being a magnetic head facing the first recording surface in the group of magnetic heads, the second magnetic head being a magnetic head facing the second recording surface in the group of magnetic heads, and
executing, subsequent to the waiting operation, switching of a magnetic head in use from the first magnetic head to the second magnetic head and starting of movement of the group of magnetic heads using the motor.
12 . The method according to claim 11 , wherein the waiting operation is performed in response to an absolute value of the relative velocity becoming larger than a threshold.
13 . The method according to claim 12 , wherein the waiting operation is an operation of waiting until the absolute value of the relative velocity becomes smaller than the threshold.
14 . The method according to claim 12 , further comprising calculating the threshold based on one or more of a seek distance, a combination of positions of the group of magnetic heads at a start and an end of the seek operation, a combination of the magnetic heads before and after the switching of the magnetic head in use, a temperature of the magnetic disk device, or a temperature of the motor.
15 . The method according to claim 11 , wherein
the two or more recording surfaces are each provided with tracks, and
the method further comprises calculating the relative velocity based on a relative position between a first track on the first recording surface and a second track on the second recording surface.
16 . The method according to claim 15 , wherein the calculating the relative velocity includes
estimating an amount of eccentricity and an eccentric direction for each of the first track and the second track, and
calculating the relative position based on the amount of eccentricity and the eccentric direction of the first track and the amount of eccentricity and the eccentric direction of the second track.
17 . The method according to claim 16 , wherein the estimating the amount of eccentricity and the eccentric direction is performed by
estimating the amount of eccentricity and the eccentric direction for each of the first track and the second track based on an amount of current supplied to the motor, accelerations of the group of magnetic heads, or positions of the group of magnetic heads.
18 . The method according to claim 16 , wherein the estimating the amount of eccentricity and the eccentric direction includes
acquiring, for each of the first track and the second track, information about an amount of current supplied to the motor,
acquiring information about positions of the group of magnetic heads based on the information about the amount of current supplied to the motor and a coefficient, and
estimating the amount of eccentricity and the eccentric direction based on the positions of the group of magnetic heads.
19 . The method according to claim 16 , wherein the estimating the amount of eccentricity and the eccentric direction includes
acquiring, for each of the first track and the second track, information about accelerations of the group of magnetic heads,
acquiring information about positions of the group of magnetic heads based on the information about the accelerations of the group of magnetic heads and a coefficient, and
estimating the amount of eccentricity and the eccentric direction based on the information about the positions of the group of magnetic heads.
20 . The method according to claim 11 , wherein
the magnetic disk device further includes a memory provided with a command queue in which one or more unexecuted commands are stored,
the method further comprises:
calculating a time required for the waiting operation for each of the one or more unexecuted commands stored in the command queue, and
determining an execution order of the one or more unexecuted commands based on a calculated value of the time required for the waiting operation.