International Business Machines Corporation

Hitachi Global Storage Technologies Netherlands B.v.

James Joseph Mosser

David Robison Hall

Weldon Mark Hanson

Adam Michael Espeseth

Thomas C Christensen

Donald Earl Vosberg

Steven Glenn Smith

A method and apparatus are provided for hard disk drive command queue ordering. For each command in the hard disk drive command queue, an expected access time is calculated including a probability of success calculation. A command in the hard disk drive command queue having a minimum calculated expected access time is identified. Then the identified command having a minimum calculated expected access time is executed. For an estimated seek time of less than a time for one full revolution, a probability of a miss multiplied by a time of one extra revolution is calculated and the result is added to an estimated seek time to provide the expected access time. For an estimated seek time of greater than a time for one full revolution, a probability of a make multiplied by a time of one extra revolution is calculated and the result is subtracted from an estimated seek time to provide the expected access time.

Space-efficient expected access time algorithm for hard disk drive command queue ordering

Disclosed is a method for recovering data from a portion of a magnetic surface that contained a read error. After a read error is encountered a magnetic transducer undergoes a head state change. The head state change is accomplished by either writing to a reserve area of the magnetic surface and or reading a portion of the magnetic surface and then rewriting to that portion of the magnetic surface. After the magnetic transducer undergoes a head state change, the portion of the magnetic surface that contained the read error is reread.

Method and apparatus for recovering data

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Rochester, MN, United States of America

James Joseph Mosser