Magnetic disk device and method of changing recording mode

1 . A magnetic disk device comprising:

a disk;

a head including a read head that reads data from the disk, a write head that writes data to the disk, and an assist element that generates energy to enhance write performance by the write head; and

a controller that selects and performs a first recording mode and a second recording mode different from the first recording mode, and selects and performs one of the first recording mode and the second recording mode according to an assist effect of the assist element, wherein

the first recording mode is a conventional magnetic recording in which a track is written at an interval in a radial direction of the disk,

the second recording mode is a shingled write magnetic recording in which a track is written in an overlapping manner in the radial direction,

the controller selects and performs one of the first recording mode and the second recording mode according to an error rate corresponding to the head, and

the controller performs the second recording mode when determining that the error rate is larger than a first threshold indicating a sign of deterioration of the assist element.

2 . The magnetic disk device according to claim 1 , wherein the controller decreases a first current to be supplied to the assist element and increases a second current to be supplied to the write head when determining that the error rate is larger than the first threshold.

3 . The magnetic disk device according to claim 1 , wherein

the disk has a first surface including a first media cache and a first user data region, and a second surface different from the first surface, the second surface including a second media cache and a second user data region, and

the head has a first head that writes data on the first surface and a second head that writes data on the second surface, and when determining that a first error rate corresponding to the first head is larger than the first threshold, the controller temporarily writes first data to the second media cache with the second head, and writes the first data read from the second media cache to the first user data region with the first head.

4 . A magnetic disk device comprising:

a disk;

a head including a read head that reads data from the disk, a write head that writes data to the disk, and an assist element that generates energy to enhance write performance by the write head; and

a controller that selects and performs a first recording mode and a second recording mode different from the first recording mode, and selects and performs one of the first recording mode and the second recording mode according to an assist effect of the assist element, wherein

the first recording mode is a conventional magnetic recording in which a track is written at an interval in a radial direction of the disk,

the second recording mode is a shingled write magnetic recording in which a track is written in an overlapping manner in the radial direction, and

the controller selects and performs one of the first recording mode and the second recording mode according to a resistance value of the assist element.

5 . The magnetic disk device according to claim 4 , wherein the controller performs the second recording mode when determining that the resistance value is larger than a second threshold indicating a sign of deterioration of the assist element.

6 . The magnetic disk device according to claim 5 , wherein the controller decreases a first current to be supplied to the assist element and increases a second current to be supplied to the write head when determining that the resistance value is larger than the second threshold.

7 . The magnetic disk device according to claim 5 , wherein

the disk has a first surface including a first media cache and a first user data region, and a second surface different from the first surface, the second surface including a second media cache and a second user data region,

the head has a first head that writes data on the first surface and a second head that writes data on the second surface, and

when determining that a first resistance value corresponding to the first head is larger than the second threshold, the controller temporarily writes first data to the second media cache with the second head, and writes the first data read from the second media cache to the first user data region with the first head.

8 . A magnetic disk device comprising:

a disk having a first surface including a first media cache and a first user data region and a second surface different from the first surface, the second surface including a second media cache and a second user data region;

a first head having a first read head that reads data from the first surface, a first write head that writes data to the first surface, and a first assist element that generates energy to enhance write performance with the first write head;

a second head having a second read head that reads data from the second surface, a second write head that writes data to the second surface, and a second assist element that generates energy to enhance write performance with the second write head; and

a controller that temporarily writes first data to the second surface with the second head when the first head writes the first data to the first surface.

9 . The magnetic disk device according to claim 8 , wherein a change amount of a first resistance value of the first assist element is larger than a change amount of a second resistance value of the second assist element.

10 . The magnetic disk device according to claim 8 , wherein a change amount of a first bit error rate (BER) corresponding to the first head is larger than a change amount of a second BER corresponding to the second head.

11 . The magnetic disk device according to claim 8 , wherein the controller performs a refresh process on a first track including the first data when an access frequency to the first data is equal to or less than a first threshold.

12 . The magnetic disk device according to claim 8 , wherein when first data is written in the first user data region with the first head, the controller temporarily writes the first data in the second media cache with the second head.

13 . The magnetic disk device according to claim 8 , wherein when first data is written in the first user data region with the first head, the controller temporarily writes the first data in the second user data region with the second head.

14 . A magnetic disk device comprising:

a disk having a first surface including a first media cache and a first user data region and a second surface different from the first surface, the second surface including a second media cache and a second user data region;

a first head having a first read head that reads data from the first surface, a first write head that writes data to the first surface, and a first assist element that generates energy to enhance write performance by the first write head;

a second head having a second read head that reads data from the second surface, a second write head that writes data to the second surface, and a second assist element that generates energy to enhance write performance with the second write head; and

a controller that refreshingly writes data written on the first surface with the first head by a shingled recording mode, to the second surface with the second head by a conventional recording mode, or refreshingly writes data written on the second surface with the second head by a conventional recording mode, to the first surface with the first head by a shingled recording mode.

15 . The magnetic disk device according to claim 14 , wherein a change amount of a first resistance value of the first assist element is larger than a change amount of a second resistance value of the second assist element.

16 . The magnetic disk device according to claim 14 , wherein a change amount of a first BER corresponding to the first head is larger than a change amount of a second BER corresponding to the second head.