Patent ID: 7043602

Claim:
A diskarray system for receiving a write command from a computer, comprising: a disk device for storing write data received from said computer; a cache memory; and a controller configured to control input and output to and from said disk device, said controller including write management information indicative of whether or not the write data to be stored in a storage area of the disk device is already written at least either in a storage area of the disk device or in said cache memory corresponding to the storage area of said disk device for each of a plurality of storage areas in said disk device, wherein said disk device is a Write Once Read Many disk device in which data once written therein is inhibited from being rewritten, said controller decides whether or not write data is already written at least either in a storage area of said Write Once Read Many disk device specified by a received write command or in said cache memory corresponding to the specified storage area of said disk device by referring to said write management information, and, when the write data is not written yet in the storage area to be written, said controller receives the write data according to said write command and stores the write data in said cache memory.