Patent ID: 8180979

Claim:
A storage system comprising: an external storage device including a plurality of external physical storage devices and a controller which configures an external logical volume on said external physical storage devices and controls to access to said external physical storage devices according to a RAID configuration; and a plurality of virtualization storage devices coupled to said storage device, said virtualization storage devices including a first virtualization storage device which includes a plurality of first physical storage devices and provides a first logical volume configured on said first physical storage devices and a first virtual volume which is mapped to said external logical volume and a second virtualization storage device which includes a plurality of second physical storage devices and provides a second logical volume configured on said second physical storage devices and a second virtual volume which is mapped to said external logical volume, wherein a first path is defined between a host computer and said first virtual volume mapped to said external logical volume in said external storage device and a second path is defined between said host computer and said second virtual volume mapped to said external logical volume in said external storage device, wherein information regarding an owner right, which indicates authority to use said external logical volume, can be transferred by said first virtualization storage device to said second virtualization storage device or by said second virtualization storage device to said first virtualization storage device, while both said first path and said second path are defined, wherein if said first virtualization storage device has said owner right and receives a first write command to said first virtual volume through said first path, said first virtualization storage device transfers a third write command corresponding to said first write command to said external logical volume, wherein if said second virtualization storage device has said owner right and receives a second write command to said second virtual volume through said second path, said second virtualization storage device transfers a fourth write command corresponding to said second write command to said external logical volume, wherein if said first virtualization storage device does not have said owner right and receives said first write command through said first path, said first virtualization storage device rejects processing of said first write command so that said host computer sends said second write command through said second path, and wherein if said second virtualization storage device does not have said owner right and receives said second write command through said second path, said second virtualization storage device rejects processing of said second write command so that said host computer sends said first write command through said first path.