Patent ID: 8300350

Claim:
A magnetic disk drive comprising: a write count memory configured to store a write count for each track or for each zone on a disk; a table in which a result of measuring an erase width corresponding to the write count for each track or for each zone has been stored as a read offset parameter value, the read offset parameter value being used to determine an offset from a predetermined position on a target track in a read position in which a head is to be positioned, the result of measuring the erase width including a first erase width E(+) in an inner direction of the disk and a second erase width E(−) in an outer direction of the disk, the first erase width E(+) and the second erase width E(−) both using the predetermined position in the corresponding track or each track belonging to the corresponding zone as a reference; a table access module configured to obtain a first erase width E(+) corresponding to a first write count stored in the write count memory and a second erase width E(−) corresponding to a second write count stored in the write count memory by accessing the table in accordance with the first write count and the second write count when the head is positioned on the target track for data read, the first write count being a write count for an outer adjacent track or for a zone to which the outer adjacent track belongs and the second write count being a write count for an inner adjacent track or for a zone to which the inner adjacent track belongs, the outer adjacent track being adjacent to the target track on an outer diameter zone of the disk and the inner adjacent track being adjacent to the target track on an inner diameter zone of the disk; a read offset setting module configured to set the offset based on the obtained first erase width E(+) and second erase width E(−); and a controller configured to position the head in a position shifted from the predetermined position by the set offset.