A switch connectable between hosts and storage device, the switch for providing a service of allotting virtual areas to be deployed in the storage device to any of the hosts upon demand, the switch includes: a processor for controlling allotment of virtual areas to the hosts and allocation of physical areas of the storage device to the virtual areas; and a memory for storing information of the host allowed access to the virtual areas, the processor controlling access by any of the hosts to the virtual area so as to restrict access by any of the hosts to a part of the virtual areas allotted to the any of the hosts in reference to the memory.