Abstract: According to one embodiment, a magnetic disk device includes a disk including a first track including a first parity sector and a second track including a second parity sector, a head that writes data to the disk and reads data from the disk, and a controller that writes, to the first parity sector, a third parity sector obtained by XORing a first sector group included in each of the first track and the second track, and writes, to the second parity sector, a fourth parity sector obtained by XORing a second sector group different from the first sector group, included in each of the first track and the second track.

Abstract: A magnetic disk device includes a disk including a plurality of zones, each including a plurality of track groups and a controller. The controller is configured to determine that data stored in a first track group is to be rewritten to the first track group, based on a refresh threshold and a first number of times data has been written to the first track group since the last rewrite of the data stored in the first track group, rewrite the data stored in the first track group to the first track group, and change the refresh threshold based on second numbers, each of which is the number of times data has been written to a different one of the track groups in a zone including the first track group, since a last reset thereof.

Abstract: According to one embodiment, a disk device comprises a memory, detector, calculation module, and deactivation module. The memory is configured to store an offset control amount at a time of manufacture. The detector is configured to detect a disk run-out. The calculation module is configured to obtain an offset control amount when the detector detects the disk run-out. The deactivation module is configured to deactivate the offset control based on a difference between the offset control amount obtained by the calculation module and the offset control amount at a time of manufacture stored in the memory and based on the offset control amount obtained by the calculation module.

Abstract: According to one embodiment, a disk device comprises a memory, detector, calculation module, and deactivation module. The memory is configured to store an offset control amount at a time of manufacture. The detector is configured to detect a disk run-out. The calculation module is configured to obtain an offset control amount when the detector detects the disk run-out. The deactivation module is configured to deactivate the offset control based on a difference between the offset control amount obtained by the calculation module and the offset control amount at a time of manufacture stored in the memory and based on the offset control amount obtained by the calculation module.