Magnetic disk device

1 . 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 are to be written, an n-th target sector of the first data track being adjacent to an n-th target sector of the second data track in a radial direction of the disk, the first data track being located in a first direction parallel to the radial direction with respect to 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 which derives position information on the write head in the radial direction by seeking the read head and which reads the data written to the recording layer;

a write processing unit which executes write processing of writing data to the recording layer, and setting a target position of the write head in the radial direction to a reference radius position when writing data to the n-th target sector of the second data track;

an adjustment unit capable of adjusting a current first assurance position which is located in the first direction relative to the reference radius position, and a current first write suspending position which is located between the reference radius position and the current first assurance position, the current first assurance position being a limit position of the write head, which assures enabling data of the n-th target sector of the first data track to be read, the current first write suspending position being a limit position of the write head in the first direction where writing data to the n-th target sector of the second data track can be permitted; and

a determination unit,

wherein

when the determination unit determines that data has been written to the n-th target sector of the second data track,

the adjustment unit is capable of tightening each of the current first assurance position and the current first write suspending position and updating the positions to positions displaced towards the reference radius position side, and

when the determination unit further determines that the position of the write head has exceeded the current first write suspending position,

the write processing unit suspends write processing.

2 . The magnetic disk device of claim 1 , wherein

when the determination unit determines that data has been written to the n-th target sector of the second data track and that the position of the write head has exceeded the current first write suspending position,

the adjustment unit tightens each of the current first assurance position and the current first write suspending position and updates the positions to positions displaced towards the reference radius position side, and

when the determination unit determines that data has been written to the n-th target sector of the second data track and that the position of the write head has not exceeded the current first write suspending position,

the adjustment unit maintains the current first assurance position and the current first write suspending position.

3 . The magnetic disk device of claim 1 , further comprising:

a storage medium;

a counter counting the number of write count of the n-th target sector of the first data track when the data is written to the n-th target sector of the second data track, and updating the total number of the write count in the storage medium; and

a refresh processing unit reading target data of the n-th target sector of the first data track, rewriting the target data to the n-th target sector of the first data track, and resetting the total number of the write count recorded in the storage medium when the determination unit determines that the total number of the write count exceeds the reference number of times,

wherein

the current first assurance position is an initial first assurance position or an updated first assurance position which is tightened relative to the initial first assurance position,

the current first write suspending position is the initial first write suspending position or an updated first write suspending position tightened relative to the initial first write suspending position, and

when the refresh processing unit rewrites the target data to the n-th target sector of the first data track and resets the total number of the write count,

the adjustment unit resets the current first assurance position to the initial first assurance position, and resets the current first write suspending position to the initial first write suspending position.

4 . The magnetic disk device of claim 3 , wherein

when the determination unit determines that the updated first write suspending position is located on the reference radius position side relative to a reference first write suspending position,

the refresh processing unit rewrites the target data to the n-th target sector of the first data track and resets the total number of the write count,

the adjustment unit resets the current first assurance position to the initial first assurance position and resets the current first write suspending position to the initial first write suspending position, and

the reference first write suspending position is located on the reference radius position side relative to the initial first write suspending position.

5 . The magnetic disk device of claim 1 , wherein

the current first assurance position is an initial first assurance position or an updated first assurance position which is tightened relative to the initial first assurance position,

the current first write suspending position is the initial first write suspending position or an updated first write suspending position tightened relative to the initial first write suspending position,

in the radial direction, if a distance from the reference radius position to the initial first assurance position is defined as an initial first assurance distance, if a distance from the reference radius position to the updated first assurance position is defined as an updated first assurance distance, if a distance from the reference radius position to the initial first write suspending position is defined as an initial first write suspending distance, and if a distance from the reference radius position to the updated first write suspending position is defined as an updated first write suspending distance, and

the adjustment unit calculates a residual ratio, which is a ratio of the updated first assurance distance to the initial first assurance distance, calculates the updated first write suspending distance by multiplying the residual ratio by the initial first write suspending distance, and derives the updated first write suspending position.

6 . The magnetic disk device of claim 5 , wherein

a current write allowable count, which is the number of times of allowing writing the data to the n-th target sector of the second data track, is an initial write allowable count or an updated write allowable count decreased from the initial write allowable count, and

the adjustment unit calculates a consumed write count based on a distance from the reference radius position of the write head when data is written to the n-th target sector of the second data track, updates the current write allowable count by subtracting the consumed write count from the current write allowable count, tightens the current first assurance position based on the updated current write allowable count, and updates the current first assurance position to a position displaced towards the reference radius position side.

7 . The magnetic disk device of claim 6 , wherein

as a distance from the reference radius position of the write head at the time when data is written to the n-th target sector of the second data track becomes greater, the consumed write count increases.

8 . The magnetic disk device of claim 7 , wherein

when the consumed write count is expressed on a logarithmic axis of common logarithm, the consumed write count changes linearly with respect to the distance from the reference radius position of the write head.

9 . The magnetic disk device of claim 6 , wherein

the determination unit permits the write processing executed by the write processing unit during a period when it is determined that the current write allowable count does not fall below a reference count,

the determination unit prohibits the write processing executed by the write processing unit during a period when it is determined that the current write allowable count falls below the reference count, and

the reference count is a numerical value between the initial write allowable count and 0 times.

10 . The magnetic disk device of claim 1 , wherein

the read processing unit derives position information of the write head in the radial direction of a specific period immediately before writing data to the n-th target sector of the second data track, and predicts a position of the write head when data is assumed to be written to the n-th target sector of the second data track,

when the determination unit determines that the predicted position of the write head exceeds the current first write suspending position, the write processing unit suspends the write processing to the n-th target sector of the second data track, and

when the determination unit determines that the predicted position of the write head does not exceed the current first write suspending position, the write processing unit executes the write processing to the n-th target sector of the second data track.

11 . The magnetic disk device of claim 1 , wherein

the disk further has a third data track including a plurality of target sectors that are targets to which data is to be written and adjacent to the second data track,

an n-th target sector of the third data track is adjacent to the n-th target sector of the second data track in the radial direction,

the third data track is located in a second direction opposite to the first direction with respect to the second data track,

the adjustment unit is capable of further adjusting a current second assurance position which is located in the second direction relative to the reference radius position, and a current second write suspending position which is located between the reference radius position and the current second assurance position,

the current second assurance position is a limit position of the write head, which assures enabling data of the n-th target sector of the third target track to be read when writing data to the n-th target sector of the second data track,

the current second write suspending position is a limit position of the write head in the second direction where writing the data to the n-th target sector of the second data track can be permitted,

when the determination unit determines that data has been written to the n-th target sector of the second data track,

the adjustment unit

tightens each of the current first assurance position and the current first write suspending position and updates the positions to positions displaced towards the reference radius position side, or

tightens each of the current second assurance position and the current second write suspending position and updates the positions to positions displaced towards the reference radius position side, or

tightens each of the current first assurance position, the current first write suspending position, the current second assurance position, and the current second write suspending position, and updates the positions to positions displaced towards the reference radius position side, and

when the determination unit further determines that the position of the write head has exceeded the current second write suspending position, the write processing unit suspends write processing.

12 . The magnetic disk device of claim 11 , wherein

when the current first write suspending position is updated to the position displaced in the second direction, the adjustment unit updates the reference radius position to a position displaced in the second direction, and

when the current second write suspending position is updated to the position displaced in the first direction, the adjustment unit updates the reference radius position to a position displaced in the first direction.

13 . The magnetic disk device of claim 12 , wherein

the adjustment unit updates the reference radius position to a neutral line where a distance from the current first write suspending position is equal to a distance from the current second write suspending position in the radial direction.