There is provided a file server which is capable of suppressing power consumption of a storage apparatus. When a file sharing program receives a file access from a client, the program makes reference to a mapping table. Then, the program addresses the access to the target file in the volume of a RAID group in which the target file is stored. A coupling-request reception program memorizes a coupling time for each user into a coupling history table. A grouping program applies a grouping to users whose coupling time-zones are similar to each other. A data transfer program transfers, into the same RAID group, data of the files associated with the grouped users, thereby collecting the data of the files into the same RAID group. On account of this, the time-zone during which no access is made to the RAID group (i.e., non-coupling time-zone) can be made longer. Accordingly, a spin-up/down request program makes a spin-down request to the RAID group in the non-coupling time-zone.