| CPC G11B 20/10009 (2013.01) [G11B 5/02 (2013.01)] | 14 Claims |
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1. A magnetic disk device comprising:
a disk having a media cache region including a plurality of tracks continuous in a radial direction in a recording layer;
a head that writes data to the recording layer of the disk and reads data from the recording layer;
a volatile buffer memory in which write data including a write command and user data corresponding to the write command is written;
a nonvolatile memory;
a main power supply; and
a control unit,
the control unit including
a write processing unit that controls write processing of data to the recording layer,
a management unit that includes, among the write data written in the volatile buffer memory, write data before being written in the media cache region as a protection target and removes the write data after being written in the media cache region from the protection target,
a data protection processing unit that saves the write data managed as the protection target by the management unit to the nonvolatile memory when the main power supply is lost,
a counter capable of individually counting up a count value of each of the tracks in the media cache region, the counter being capable of counting up the count value of a track adjacent to a track on which write data has been written each time the write data is written to the media cache region, and
a determination unit that determines whether a difference between a maximum value and a minimum value among a plurality of count values of the tracks of the media cache region reaches a threshold,
the management unit, when the determination unit determines that the difference has reached the threshold, returning the write data of the volatile buffer memory, which is original data of the write data of the track in which the count value becomes the maximum value among the tracks, to the protection target.
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