A storage system is disclosed for performing control to match data among cache memories corresponding to shared volumes when multiple disk controllers containing cache memories are accessing shared volumes formed in the storage device. The storage system contains a switch for switching and connecting the multiple disk controllers containing cache memories, with a disk array containing the shared volumes capable of being commonly accessed from the multiple disk controllers. The switch performs exclusive access control of the multiple disk controllers' writing on the shared volumes, and performs control to match data other than modified data among the cache memories.