Abstract: One illustrative embodiment of the present invention pertains to a device. The device is configured to evaluate a Gray code value and to provide compensation for error in the Gray code value. Another illustrative embodiment of the present invention pertains to a method. The method includes comparing Gray code information with servo information. The method also includes evaluating error in the Gray code information based on the comparison between the Gray code information with servo information. Another illustrative embodiment of the present invention pertains to a data storage system. The data storage system includes a data storage medium, a head, and a controller. The head is controllably positionable relative to the data storage medium. The controller includes a means for sensing position information from the head. The controller also includes a means for compensating for error in the position information, to position the head relative to the data storage medium.

Abstract: An apparatus and method for selecting physical cylinders (cylinders accessible for read/write operations) in a disc drive is provided. The disc drive includes at least one rotatable disc. The disc drive also includes a first head, which is positionable adjacent a first disc surface, and a second head, which is positionable adjacent a second disc surface. The first disc surface has a first plurality of greycode tracks and the second disc surface has a second plurality of greycode tracks. Each greycode track of the second plurality of greycode tracks corresponds to a different greycode track of the first plurality of greycode tracks, thereby forming a plurality of greycode cylinders, with each greycode cylinder of the plurality of greycode cylinders including a pair of corresponding greycode tracks. The physical cylinders are a subset (less than all) of the plurality of the greycode cylinders.