Patent ID: 8117391

Claim:
A storage system, which is coupled to a computer, comprising: a storage device for storing data for which write is requested by the computer; a controller for controlling transfer of data in the storage system; a plurality of cache memory units for temporarily storing data to be stored into the storage device; and a connecting unit for connecting at least the plurality of cache memory units, each of the plurality of cache memory units comprising: a cache memory for storing data; an auxiliary storage device for holding data even after shutdown of power; and a cache controller for controlling an input/output of data to/from the cache memory and the auxiliary storage device, wherein the cache controller is configured to store data stored in the cache memory, which is divided into a plurality of parts, into a plurality of the auxiliary storage devices included in the plurality of cache memory units, wherein: the plurality of cache memory units comprise: a first cache memory unit; and a second cache memory unit for storing the same data as stored in the first cache memory unit; and the cache controller is configured to: store data stored in the cache memory of the first cache memory unit into the plurality of the auxiliary storage devices; and prevent to store data stored in the cache memory of the second cache memory unit into the plurality of the auxiliary storage devices.