The present invention achieves data relocation in accordance with a user's policies, in an environment where a plurality of storage devices coexist. The volumes belonging to storage devices A-D are managed virtually integrally. A host recognizes a plurality of storage devices A-D as a single virtual storage device. The user is able to group arbitrarily each volume belonging to the storage system, as a plurality of storage layers 1-3. For example, storage layer 1 can be defined as a high-reliability layer, storage layer 2, as a low-cost layer, and storage layer 3, as an archive layer. Each storage layer is constituted by a group of volumes corresponding to respective policies (high reliability, low cost, archiving). The user designates volumes V1 and V2 to be moved, in group units, and indicates a storage layer forming a movement destination, whereby the data is relocated.