A system for storing data includes a virtualization apparatus coupled to a computer and to a plurality of storage devices. In response to a request from the computer, the virtualization apparatus issues a notice that a predetermined size of a virtual volume has been allocated to the computer. Upon receiving an access request issued from the computer to the virtual volume, the virtualization apparatus allocates storage areas existing in the plurality of storage devices to the virtual volume, converts the access request received from the computer into 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.