Patent ID: 7383361

Claim:
A disk array system comprising: a plurality of disk devices for storing data; and a disk array controller coupled to the plurality of disk devices, wherein when a command is issued to one of the plurality of disk devices, the disk array controller measures a response time from issue of the command, wherein when the disk array controller receives a response from the one of the plurality of disk devices between a first predetermined time and a second predetermined time, the disk array controller sends data from the one of the plurality of disk devices to a computer and increases a counter, wherein when the response time is over the second predetermined time without receiving the response, the disk array controller executes a correction operation to generate data requested by the command based on a RAID configuration of the plurality of disk devices, and sends the data generated by the correction operation to the computer, wherein when the disk array controller receives the response after the second predetermined time, the disk array controller increases the counter, and wherein when a value of the counter exceeds a predetermined value, the disk array controller executes a copy operation to copy data from the one of the plurality of disk devices to another one of the plurality of disk devices.