Patent ID: 7328326

Claim:
A storage device comprising: a storage control unit; and a storage unit, wherein said storage control unit includes: a host interface (I/F) control section executing communication with an upper apparatus; a disk I/F control section executing communication with said storage unit; a data transfer mechanism executing a data transfer processing between said host and said storage unit; a cache memory temporarily storing data to be transferred between said host and said storage unit; a performance measuring mechanism; and a copy mechanism, said storage unit includes: a physical volume and an auxiliary physical volume that are physical memory regions provided by a plurality of physical disk drives for storing data; and a plurality of logical volumes each being a logical memory region to be set in each of said physical volume and said auxiliary physical volume, wherein a load condition of said each logical volume is measured by said performance measuring mechanism based on a data amount and a command processing amount to be transferred by said data transfer mechanism, a content of said each logical volume set in said physical volume is copied to said each logical volume set in said auxiliary physical volume by said copy mechanism based on a measurement result of said performance measuring mechanism, and said each logical volume set in said auxiliary physical volume copied by said copy mechanism and said each logical volume set in said physical volume serving as a copy source are provided as one virtual logical volume to said upper apparatus, thereby distributing a load from said upper apparatus.