Abstract: Virtual tape volumes are grouped depending on their attributes, in order to improve access efficiency of the host computer. A storage apparatus includes a virtual storage area for storing a virtual tape volume, a data transfer control program for controlling the data transfer among the virtual storage area, a host computer and a real tape volume, and a virtual tape information database for storing attribute information of the virtual tape volume. The data transfer control program forms groups of the virtual tape volumes having the identical attribute, transfers and develops, to the virtual storage area from the real tape volume, all virtual tape volumes included in the group for the request from the host computer to any one of the virtual tape volumes in the group, and generates a high speed response to such request when the host computer has issued a request to such group.

Abstract: A disk system comprising a plurality of disk units (1-0 to 1-7) divided into primary logical volumes (101 to 171) and secondary logical volumes (102 to 172) which are controlled by a plurality of disk controllers (4-AA to 4-BB). One of disk controllers sets an assign bit to cause one of the logical volumes to perform a stand-alone operation. This assign bit can be reset by another disk controller for another logical volume, which generates an unconditional reserve command. In this system, flip-flops (18, 19) for storing a stand-alone control signal, decoders (7-AA.about.7-BB) for an unconditional reserve command, interruption signal generating circuits (27, 28), a notification circuit (9), and the like are provided so that the issuance of an unconditional reserve command is notified to the corresponding disk controller.