Patent ID: 8542458

Claim:
A magnetic disk drive comprising: a disk comprising a first surface and a second surface; a first microactuator configured to allow a first head to make micromotion based on a first operation amount, the first head associated with the first surface; a second microactuator configured to allow a second head to make micromotion based on a second operation amount, the second head associated with the second surface; and a servo controller configured to provide the first operation amount to the first microactuator and to provide the second operation amount to the second microactuator, the second operation amount obtained by inverting a polarity of a first frequency component with a particular frequency contained in the first operation amount and by not inverting polarities of frequency components other than the first frequency component if the first operation amount is generated in a particular mode in which the first surface is used as a tracking surface, wherein: the servo controller comprises a filter module configured to output the second operation amount based on the first operation amount; frequency components contained in the first operation amount comprise the first frequency component, where the first frequency component inhibits a positioning error on the first surface having a phase reverse to a phase of a positioning error on the second surface, and frequency components of the first operation amount other than the first frequency component inhibit a positioning error on the first surface having a phase the same as a phase of a positioning error on the second surface; and the first frequency component results from disk flutter.