Importance

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Abstract

A disk array system includes a disk array, an array controller, an offtrack detecting unit, an error processing unit, an offtrack measuring unit, a reformat control unit, and a reformat processing unit. The disk array includes a plurality of disk devices storing a plurality of data in parallel and storing redundant data used for restoring data lost if one of the plurality of data is lost. The array controller controls input from or output to the disk array based on a request from an upper system, such as a host computer. The offtrack detecting unit is provided in each of the disk devices for detecting offtrack and informing the array controller of the offtrack. Further, an error processing unit is provided in the array controller for logically disconnecting a disk device having communicated information if offtrack detection information is received from the offtrack detecting unit, and for issuing a diagnostic I/O command. In addition, an offtrack measuring unit is provided in each of the plurality of disk devices for measuring the offtrack from servo information recorded in an offtrack measurement cylinder. The reformat control unit is provided in the array controller for issuing a reformat command to the disk device. In addition, the reformat processing unit of the present invention is provided in each of the disk devices for rewriting servo cylinder information onto the data surface of the disk medium.

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First Claim