Patent ID: 8725675

Claim:
A storage system coupled to a client, the storage system comprising: a storage apparatus that stores data in a plurality of volumes that form a plurality of RAID groups; and a file server that receives file access requests from the client and controls storage of file data in the storage apparatus, and wherein the file server is configured to: define a set of first users that have similar corresponding time-zones during which access to the data stored in the storage apparatus is not made as a first group; relate the first group to a first RAID group of the plurality of RAID groups; and associate the first group with a first time-zone that is calculated based on a time-zone required for spin-down and spin-up to be performed in the first RAID group and the corresponding time-zones during which access to the data stored in the storage apparatus is not made for the set of first users, wherein a length of the first time-zone is determined in accordance with both a length of the corresponding time-zones and a length of a time period needed for spin-down and spin-up to be performed in the RAID group, wherein the storage apparatus is configured to: migrate data of a file accessed by a user of the set of first users to the first RAID group; and operate the first RAID group in a power saving state during the first time-zone, and wherein the power saving state is a spin-down state.