Patent ID: 8392678

Claim:
A storage system allocating some or all of storage regions supplied by physical disks storing data from host apparatus as a pool region, and forming virtual volumes dynamically allocated from the pool regions in response to write requests to the virtual volumes, comprising: a first correlating section for correlating a plurality of RAID groups composed of a plurality of the physical disks, and the pool region; and a second correlating section for correlating the pool region and the storage regions of the virtual volumes, wherein each virtual volume is a mirror configuration comprising a base volume and a mirror volume, wherein the first correlating section correlates a first RAID group of the RAID groups to a first pool region and the second correlating section correlates the base volume and mirror volume to the first pool region, and wherein the second correlating section is configured to: allocate a first base virtual region of the base volume corresponding to a first virtual region of a first virtual volume to a first storage region included in the first RAID group, and allocate a first mirror virtual region of the mirror volume corresponding to the first virtual region of the first virtual volume to a second storage region included in a RAID group which is one of the RAID groups in the first pool region except the first RAID group, based on first write requests to the first virtual region from the host apparatus; and allocate a second base virtual region of the base volume corresponding to a second virtual region of the first virtual volume to a third storage region included in a RAID group which is one of the RAID groups in the first pool region except the second RAID group, and allocate a second mirror virtual region of the mirror volume corresponding to a second virtual region of the first virtual volume to a fourth storage region included in the first RAID group, based on second write requests to the second virtual region from the host apparatus.