Patent ID: 9214188
Filing Date: 2015-12-15
Classification: G11B

Abstract:
1. A method of selecting a rotation speed for servo writing a disk of a disk drive, the method comprising: injecting a gas into a head disk assembly (HDA) comprising the disk; rotating the disk at a rotation speed and reading data from the disk using a head to generate a read signal comprising a first frequency oscillation due to reading the data from the disk and a second frequency oscillation due to a fly height of the head varying as the disk rotates, wherein the first frequency is higher than the second frequency; measuring an amplitude of the second frequency oscillation to measure a fly height modulation (FHM) of the head; when the amplitude of the second frequency oscillation exceeds a threshold, adjusting the rotation speed; servo writing the disk at the adjusted rotation speed; after servo writing the disk and evacuating the gas from the HDA, rotating the disk at a normal rotation speed lower than the adjusted rotation speed used for servo writing the disk; and writing manufacturing data to the disk at the normal rotation speed.