Abstract: A disk drive is disclosed comprising a first head actuated over a first disk surface comprising servo information, a second head actuated over a second disk surface, and a voice coil motor (VCM) operable to actuate the first and second heads radially over the respective disk surfaces. The first disk surface and the second disk surface are rotated, and the servo information is read from the first disk surface using the first head to generate a read signal. The read signal is processed to generate a control signal applied to the VCM to move the second head radially over the second disk surface while applying an erase signal to the second head in order to erase at least part of the second disk surface.

Abstract: A disk drive is disclosed comprising a head actuated over a disk comprising a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. The head is positioned over the disk and used to read the spiral tracks to detect a plurality of spiral-to-spiral times each representing a time between consecutive spiral crossings. A velocity of the head is estimated in response to the spiral-to-spiral times, and velocity feedforward compensation values are generated from the estimated head velocity. A control signal is generated to position the head over the disk in response to the velocity feedforward compensation values. When the detected spiral-to-spiral times are substantially constant, position feedforward compensation values are initialized in response to the velocity feedforward compensation values.