Patent ID: 8185765

Claim:
A storage apparatus, comprising: an interface connected to a host computer; a plurality of memory devices; a control unit for managing a plurality of parity groups configured from the plurality of memory devices, each parity group corresponding to at least one logical volume provided to the host computer by the control unit; and a control memory storing control information and user data, the control information indicating a status of each of a plurality of logical volumes corresponding to the plurality of said parity groups and relationships between the plurality of parity groups and the plurality of logical volumes; wherein the control unit is configured to: set the status of one of the plurality of logical volumes to an online status so that the host can access to the one of the plurality of logical volumes, in response to a command from the host computer to form a logical connection to the one of the plurality of logical volumes: and set the status of one of the plurality of logical volumes to an offline status so that the host computer cannot access to the one of the plurality of logical volumes, in response to a command from the host computer to cancel the logical connection, wherein the control memory further contains an inhibition flag which is set to a certain logical volume to be used for a backup operation executed by the control unit while a status of the certain volume keeps offline status; and wherein the control unit applies power saving processing to a first plurality of memory devices of a first parity group if the status of any logical volumes corresponding to the first group is offline status and the inhibition flag is not set to the any logical volumes corresponding to the first group based on the control information.