Data storage apparatus

A method for controlling an apparatus for storing data, the apparatus including a medium for storing data having a plurality of synchronization marks and a plurality of data blocks, the synchronization mark and the data block being allocated alternately in the direction of the circumference of the medium, a head writing data into or reading out data from the medium, the method comprising:

• reading out synchronization marks of the medium,
• measuring time for the head to pass through each of the data blocks on the basis of signals read out from each of the synchronization marks in the direction of the circumference of the medium,
• generating write/read clock for each of the data blocks, which is at least in part continuously changing in speed, by calculating difference in time for the head to pass through the each one of the data blocks and another of the data blocks adjacent the one of the blocks on the basis of the time measured, and
• writing data into or reading out data from the medium in synchronization with the write/read clock generated.