Patent ID: 8078815

Claim:
A storage subsystem, comprising: a controller; a first logical storage area in a RAID (Redundancy Array of Independent Disks) group configured by a plurality of storage devices; and a second logical storage area in a plurality of RAID groups each configured by the plurality of storage devices, and storing a copy of data stored in the first logical storage area, wherein the first and second logical storage areas form a copy group, and when starting copying of the data from the first logical storage area to the second logical storage area, the controller performs a mode change, from a power saving mode to a ready mode, to the plurality of storage devices configuring the plurality of RAID groups corresponding to the second logical storage area, wherein when starting copying of the data from the first logical storage area to the second logical storage area, the controller makes, remain in the power saving mode, the plurality of storage devices configuring the RAID groups corresponding to any part of the second logical storage area being not a target for the copying of the data, wherein when starting copying of the data from the first logical storage area to the second logical storage area, the controller makes the mode change, from the power saving mode to the ready mode, starting from the storage devices configuring the RAID groups corresponding to any part of the second logical storage area being the target for the copying at the earliest timing.