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.