Patent ID: 7370148

Claim:
A storage system characterized by comprising a cache control unit for managing data in a cache memory in a page area unit, and processing an input/output request from an upper-level device to a storage device; a Redundant Arrays of Inexpensive Disks (RAID) control unit for managing data in each of a plurality of the storage devices in a strip area unit having the same size as a page area in the page area unit and managing a plurality of strip areas for data and one strip area for parity having the same address collectively in the strip area unit, and forming a redundant configuration of RAID 5 in which the storage device on which the strip area for parity is placed is changed every time the address of the stip area is changed; a write-back processing unit for, when a write-back request for writing back new data in the cache memory to the storage device is generated, reserving a parity buffer area in the cache memory, generating new parity, and then, writing the new data and the new parity to corresponding storage devices of said plurality of storage devices; and a recovery processing unit for, when an error in which the consistency of RAID 5 is broken occurs in a plurality of the storage devices upon write performed by the write-back processing unit, reserving, in the cache memory, a cache strip area storing data of the entire stip including the new data which is to be written back, and causing the cache control unit to manage it.