Patent ID: 8402220

Claim:
A storage controller coupled to an external storage apparatus, comprising: a cache storage, which is a cache of the external storage apparatus; and a control processor coupled to the cache storage, wherein the control processor has an internal access function of accessing the cache storage by executing a first program, wherein the control processor has an external access function of accessing the external storage apparatus by executing a second program, wherein the cache storage has: a physical storage device; and a cache processor coupled to the physical storage device, wherein the internal access function transmits a read command to the cache storage, wherein the cache processor performs a cache hit/miss determination to determine whether data to be read according to the read command is stored in the physical storage device or not, wherein, when the result of the cache hit/miss determination is negative, the external access function is executed by allowing the cache processor to transmit a read request issued to the external storage apparatus, wherein, when the result of the cache hit/miss determination is positive, the external access function is not executed and the cache processor transmits the data to be read within the physical storage device to the internal access function without issuing the read request to the external storage apparatus, wherein the control processor has a management function of managing the internal access function and the external access function by executing a third program, wherein the internal access function is executed by a first virtual machine, wherein the external access function is a second virtual machine for controlling the first virtual machine, and wherein the management function is a hypervisor for controlling the activation and end of the first virtual machine, as well as the activation and end of the second virtual machine.