To provide a storage system with a cost/performance meeting the system scale, from a small-scale to a large-scale configuration. In the storage system, protocol transformation units and data caching control units are connected to each other through an interconnection, the data caching control units are divided into plural control clusters, each of the control clusters including at least two or more data caching control units, control of a cache memory is conducted independently for each of the control clusters, and one of the plural data caching control units manages, as a single system, protocol transformation units and the plural control clusters based on management information stored in a system management information memory unit.