Patent ID: 8135969

Claim:
A storage apparatus, which can control access targeted at a logical unit configured from a plurality of disk devices, the disk drives configuring a RAID group, comprising: a receiving unit that receives an access command targeting a storage area of the logical unit; a state determination unit that determines whether or not a response to the access command can be made via one or more access-enabled disk devices of the plurality of disk devices configuring the logical unit; a power value acquisition unit, in response to a determination that the response to the access command cannot be made because the disk drives are in a power-saving state, acquires a value of power capable of being used to spin up all of disk devices in the RAID group; and a selection unit that if the value of power by the power value acquisition unit is within a range of usable power values, selects all of the disk drives in the power-saving state to spin up, otherwise selects less than all the disk drives to make the response to spin up from all of the disk drives in a power-saving state in ascending order according to their spin-up times; and wherein the number of the disk drives necessary to make the response to spin up is determined based on redundancy of the RAID group.