System for controlling data transfer between a host system and storage devices. A virtualization controller implements the data transfer and includes first ports for connection with the storage devices, a second port for connection with the host system, a processor, and a memory configured to store volume mapping information which correlates first identification information used by the host system to access a first storage area in one of the storage devices, with second identification information for identifying the first storage area, the correlation being used by the processor to access the first storage area. When data stored in the first storage area is transferred to a second storage area, the processor correlates the first identification information with a third identification information for identifying the second storage area and registers the first identification information and the third identification information in the volume mapping information.