Patent ID: 8041914

Claim:
A storage system comprising: a plurality of storage on which a plurality of logical volumes are based; one or more processors for writing data to a logical volume, of said plurality of logical volumes, designated by an I/O command sent from a host device or reading data from this logical volume; one or more cache memories for temporarily storing data to be written to a logical volume by said processor or data read from a logical volume by said processor; and a power-saving controller for redirecting a processing related to a state of one or more I/O process-participating devices or a part thereof, for at least one of storage unit, processor and cache memory which constitute I/O process-participating devices related to said I/O command processing, to another one or more I/O process-participating devices or a part thereof, and shifting the state of said one or more I/O process-participating devices or a part thereof to a power-saving state, wherein RAID Groups are configured from two or more storage units of said plurality of storage units, and wherein said power-saving controller migrating all logical volumes from which a low load RAID Group is formed to one or more other low load RAID Groups, thereby shifting a state of the storage units from which the low load RAID Group is configured to a power-saving state.