Optimization of disk drive spindle speed during low power mode

Abstract

To reduce disk drive power consumption, a reduced disk rotational velocity idle mode is used wherein in-situ components of the drive calibrate the landing (or take-off) speed of each head/disk combination and establish a transition speed incrementally above the highest landing speed to assure that the heads both fly above the confronting disk surfaces and avoid substantially all the asperities projecting from the disk surfaces. This can be accomplished using digital harmonic ratio flyheight (HRF) measurement techniques. This system optimizes the power savings to the characteristics of the particular drive. The power saving can be imposed in stages, initially to maintain the capability of quick return to operating conditions and a final stage that realizes maximum power savings. The transition speed is recalibrated periodically, which enables monitoring of the device for degradation or future imminent failure as sequential transition speeds change. Adaptive control can be implemented by extending the time between recalibration cycles when little change occurs during a series of transition speed calculations and reducing the time between recalibration cycles when significant change occurs in the sequence of transition speeds.