Patent ID: 7743212

Claim:
A storage system comprising: a plurality of drive devices that drive a plurality of physical disks each having a physical storage area; a RAID configuration unit that configures a plurality of RAID groups by grouping two or more of the physical disks; a logical disk creation unit that creates a logical disk on a given RAID group, the logical disk having a logical storage area associated with the physical storage area of the given RAID group; a memory for storing a RAID group control table comprising, for each RAID group, power status information for said each RAID group; a receiver to receive requests, wherein when the receiver receives a request for creating a new logical disk, a selected RAID group that is in a powered state is selected from among the plurality of RAID groups based on information comprising the RAID group control table; and an allocator configured to allocate to the new logical disk some of the physical storage area of the selected RAID group, wherein when the storage system receives a write request for the new logical disk, the storage system stores data associated with the write request on the physical storage area that is allocated to the new logical disk, wherein the allocation comprises a selector that selects, as the selected RAID group, a primary RAID group in the powered state having a free capacity that is largest among RAID groups in the powered state, wherein when the free capacity of the primary RAID group is greater than a requested capacity of the new logical disk, the physical storage area of the primary RAID group is allocated entirely to the new logical disk.