Disk device and data reassignment method

A disk device comprising:

• a first recording disk with at least one surface with a plurality of data zones comprising a plurality of tracks with each data zone having a spare area;
• a head for recording or reproducing data to or from the recording disk;
• an actuator for moving the head radially on the surface of the first recording disk;
• a motor for rotating the first recording disk;
• and
• data reassigning means for assigning an alternate data area for storing data to replace a first data area at a first angular position in a first track in a first data zone in which an error occurs, the alternate data area being selected in part based on angular position in a first spare area in the first data zone in a second track and at a second angular position which is offset from the first angular position by at least a selected angle which allows the actuator to move the head from the first track to the second track before the first recording disk rotates from the first angular position to the second angular position.