Patent ID: 6987636

Claim:
A method of writing product servo sectors to a disk of a disk drive to define a plurality of data tracks, the disk drive comprising control circuitry and a head disk assembly (HDA) comprising the disk, an actuator arm, a head coupled to a distal end of the actuator arm, and a voice coil motor for rotating the actuator arm about a pivot to position the head radially over the disk, the method comprising the steps of: (a) writing a plurality of spiral tracks to the disk, wherein: each spiral track comprises a high frequency signal interrupted at a predetermined interval by a sync mark; and a slope of the spiral tracks over a first radial segment of the disk is substantially steeper than the slope of the spiral tracks over a second radial segment of the disk; (b) using the head internal to the disk drive to read the spiral tracks to generate a read signal; (c) processing the read signal to detect the sync marks in the spiral tracks to synchronize a servo write clock; (d) processing the read signal to demodulate the high frequency signal in the spiral tracks to generate a position error signal used to maintain the head internal to the disk drive along a first target circular path; and (e) using the head internal to the disk drive and the servo write clock to write product servo sectors to the disk; wherein the steeper slope of the spiral tracks over the first radial segment causes a track density of the data tracks to be lower over the first radial segment compared to the track density of the data tracks over the second radial segment.