Patent ID: 7203015

Claim:
A disk drive comprising: a disk-shaped recording medium having data sectors each having a first sync-mark region, a second sync-mark region and a data region; a magnetic head which writes data in each data sector of the disk-shaped recording medium; sync-mark generating means for generating a bit pattern of a first sync mark for detecting a head of each data sector and a bit pattern of a second sync mark, which is different from the bit pattern of the first sync mark, the second sync mark having a bit pattern including at least a series of consecutive bits representing positive magnetization polarity and at least a series of consecutive bits representing negative magnetization polarity, a series of consecutive bits that consists of a largest number of bits of same magnetization polarity having a bit number that is at least 50% of a total bit number of the second sync mark but less than a percentage of the total bit number, set in accordance with a tolerable bit-error rate; and writing means for supplying a data signal to the magnetic head, the data signal including the first sync mark and second sync mark which have been generated by the sync-mark generating means.