In a system where a storage device is coupled to a computer, a storage area in the storage device is efficiently allocated to the computer. The system comprises a virtualization apparatus to be coupled to the virtulization apparatus. The virtualization apparatus, responding to a request from the computer, issues a notice to the effect that a predetermined size of virtual volume has been allocated to the computer. The virtualization apparatus, upon receiving an access request from the computer to the virtual volume, allocates storage areas existing in a plurality of storage devices to the virtual volume, converts the access request received from the computer to an access request addressed to a storage device having the storage devices allocated to the virtual volume, and transmits the converted access request to the storage device.