Magnetic disk device

A magnetic disk device comprising:

• a first disk having a first data track and a second data track adjacent to each other in a first recording layer, wherein the first data track and the second data track each include a plurality of target sectors to which data is written, and the first data track is located in a first direction parallel to a radial direction of the first disk when viewed from the second data track;
• a first write head that writes data to the first recording layer of the first disk;
• a write processing unit that is capable of executing write processing to write data to the first recording layer;
• an error correction unit that executes error correction of data in one or more damaged target sectors of the plurality of target sectors of the first data track that are determined to be damaged;
• a correction limit prediction unit;
• and
• a determination unit,
• wherein
• during a write period in which the write processing is executed for the plurality of target sectors of the second data track after the write processing is executed for the plurality of target sectors of the first data track,
• the correction limit prediction unit
• calculates an excess amount by which a position of the first write head protrudes from a first reference radial position in the first direction each time data is written to each of the target sectors of the second data track,
• calculates a metric value by multiplying a first weight coefficient, which is a variable whose value changes in accordance with the excess amount, by the excess amount each time the position of the first write head exceeds the first reference radial position,
• updates a cumulative metric value, which is a cumulative total of the metric values during the write period, and
• generates first prediction information, which is information predicting whether or not the error correction for the first data track will reach its limit based on the cumulative metric value, before the write processing for all target sectors of the second data track is completed, and
• the determination unit determines whether or not to allow the write processing unit to continue the write processing for the second data track based on the first prediction information.