HDD servo technology for media-level servo track writing

HDD servo technology for media-level servo track writing (STW) has been developed. The media-level STW is a process to write servo signal on magnetic disks before they are separately assembled in drives. It supplies a solution to achieve low-cost and accurate servo-signal writing. The media-level STW apparatus has an actuator with magnetic heads and an air-bearing spindle motor on which magnetic disks are mounted. The servo controller of HDD with disks of media-level STW compensates radial and rotational distortions of the servo signal (e.g. track-address, RRO, and servo signal timing). The calibrations to compensate the distortions are executed in a factory.