A storage system 1 includes: plural protocol transformation units 10 that transform, to a protocol within the system, a read/write protocol of data exchanged with servers 3 or hard disk groups 2; plural cache control units 21 that include cache memory units 111 storing data read/written with the servers 3 or the hard disk groups 2 and which include the function of controlling the cache memory units 111; and an interconnection network 31 that connects the protocol transformation units 10 and the cache control units 21. In this storage system 1, the plural cache control units 21 are divided into plural control clusters 70, control of the cache memory units 111 is independent inside the control clusters, and a system management unit 60 that manages, as a single system, the plural protocol transformation units 10 and the plural control clusters 70 is connected to the interconnection network 30.