Controlling motion of storage media

摘要

An apparatus for writing data to a data storage medium on which data is stored in data groups (N−3 to N+1) comprising tracks extending across and spaced from a reference edge of the storage medium includes a control system operable to cause i) a track reference difference value representative of a difference in a distance between the tracks of an existing data group (N−1) on the storage medium and the reference edge and a distance between the reference edge and the tracks of a data group (N) to be written to the storage medium such that it is the next data group following the existing data group (N−1) or ii) data from which such a difference value can be derived to be included in at least one of frame (A1 to A5) to be written between the existing data group and the next data group such that the tracks of the at least one frame are spaced from the reference edge by substantially the same distance as the tracks of the existing data group.