Magnetic disk device

A magnetic disk device comprising:

• a disk having a first data track and a second data track adjacent to each other in a recording layer, the first data track and the second data track each including a plurality of target sectors being targets to which data is written, the first data track being located in a first direction parallel to a radial direction of the disk as viewed from the second data track;
• a head including a write head writing data to the recording layer and a read head reading data from the recording layer;
• a read processing unit capable of executing seek processing of seeking the read head;
• a write processing unit capable of executing write processing of writing data to the recording layer;
• an error correction unit executing error correction of data in one or more corrupted target sectors whose data is determined to be corrupted, among the plurality of target sectors of the first data track;
• an adjustment unit;
• a correction limit prediction unit;
• and
• a determination unit,
• wherein
• during a first write period being a period elapsed after the write processing unit executes the write processing for the plurality of target sectors of the first data track and being the period during which the write processing unit executes the write processing for the plurality of target sectors of the second data track,
• the read processing unit executes first seek processing of seeking the read head, moves the read head at a first distance, and makes the write head face the second data track,
• the adjustment unit
• derives a first predicted excess amount at which a position of the write head is expected to be displaced beyond a reference radius position in the first direction during the first write period, the first predicted excess amount being varied in accordance with a distance for seeking the read head, and
• derives a predicted upper limit threshold value indicating a limit of a range in which the error correction for the first data track is executable, the predicted upper limit threshold value having a smaller value as each of predicted excess amounts including the first predicted excess amount is increased, the predicted upper limit threshold value being a variable,
• each time data is written to each of the plurality of target sectors of the second data track, the correction limit prediction unit measures an actual excess amount of the position of the write head, which is displaced beyond the reference radius position in the first direction, updates a cumulative actual excess amount, which is a cumulative total of the actual excess amount, and calculates a first cumulative predicted excess amount obtained by adding the first predicted excess amount to the cumulative actual excess amount, and
• the determination unit
• causes the write processing unit to continue the write processing for the second data track if determining that the first cumulative predicted excess amount is smaller than or equal to the predicted upper limit threshold value, and
• causes the write processing unit to suspend the write processing for the second data track if determining that the first cumulative predicted excess amount exceeds the predicted upper limit threshold value.