Embodiments in accordance with the present invention relate to methods wherein a capacity of a disk drive is increased by partially overwriting adjacent tracks to shorten the track width and collectively updating a data update unit made up of a plurality of tracks, wherein the capacity reduction caused by a defective track is suppressed. Track groups having two types of track widths, or Shingled Tracks(ST) and Tiled Tracks(TT), are allocated in a zone. First, the zone is divided into two areas, namely, a shingled track (ST) area and a spare or tiled track (TT) area. When a defective track is detected in the shingled track (ST) area, it is checked whether or not the spare or tiled track (TT) area affords an area to be transferred. If it does, an area is transferred from the spare or tiled track (TT) area to the shingled track (ST) area. When it is confirmed that the allocation of ST has been completed, TT is allocated to the remaining spare or tiled track (TT) area in subsequent steps.