Western Digital Technologies, Inc.

William W Clawson

Siri S Weerasooriya

Wing Ying

Tomas D Hugunin

A disk drive is disclosed comprising a disk and a head actuated over the disk. The disk comprises a plurality of spiral tracks, wherein each spiral track comprises a high frequency signal interrupted by a sync mark at a sync mark interval. A first spiral track comprises a first sync mark from an outer diameter of the disk to a reference radial location and a second sync mark from the reference radial location toward an inner diameter of the disk. A second spiral track comprises the second sync mark from the outer diameter of the disk to the reference radial location and the first sync mark from the reference radial location toward the inner diameter of the disk. The first sync mark is different than the second sync mark.

Disk drive comprising index spiral track identified by change in sync mark

Disclosed is a method for reducing spiral write time and clock reference drift while writing spiral reference patterns on a disk of a disk drive. The method includes: controlling a radial location of a head for writing a first band of tracks near one of an outer diameter (OD) circumference of the disk or an inner diameter (ID) circumference of the disk and for writing a second band of tracks near the other of the OD circumference of the disk or the ID circumference of the disk, respectively, wherein a substantial majority of the tracks each include a plurality of servo sectors including a track number and a sync mark; measuring a distance between first and second reference center positions of reference center tracks of the first and second bands of tracks; and writing a spiral reference pattern therebetween.

Reducing spiral write time and clock track drift while writing spiral reference patterns to a disk of a disk drive

A method is disclosed for reducing disk expansion effects while writing spiral reference patterns on a disk of a disk drive. The disk drive comprises control circuitry and a head disk assembly (HDA) for positioning a head radially over the disk. In the method, an external spiral servo writer is used to control a radial location of the head for writing a plurality of the spiral reference patterns between inner and outer seed tracks. A head velocity profile is adjusted for writing each spiral reference pattern to account for thermal disk expansion. The head internal to the disk drive is used to read the spiral reference patterns in order to write product servo bursts to the disk that define a plurality of radially-spaced circular data tracks.

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Fremont, CA, United States of America

William W Clawson