A storage subsystem of a control type holding redundant data wherein an access request from an upper-level device on a file basis is processed cooperatively by a plurality of storage systems forming the storage subsystem. To this end, each of the storage systems forming the storage subsystem has an element for processing the access request from the upper-level device on a file basis and updating the redundant data involved by the access request. Further, the storage system has an element for holding positional information on a recording medium for each file to be stored in its own and access history information, and rearranging storage areas under arbitrary conditions.