Patent ID: 7051165

Claim:
A data source device that provides data in response to requests from a plurality of clients comprising: a disk drive configured to store the data including a single shared volume with specified capacity that is used in common among all the plurality of clients and a plurality of specific volumes, each of which is associated with one of the plurality of clients; a virtual volume management module that allocates a virtual volume to each of the plurality of clients; a block mapping management module that manages mapping between a virtual block, which is defined in the virtual volume, and a physical block, which is physically defined in the shared volume and the specific volume; a command receiving module that receives a read out command from the client, which involves specification of the virtual block; and a read out control module that reads out the data corresponding to the virtual block from the specific volume associated with the client or the shared volume, with reference to the block mapping management module, to be output to the client that has issued the read out command, and wherein at a specified time, specific data in the single shared volume for each said plurality of clients is output to each said plurality of clients simultaneously, some of said specific data output being the same for some of said plurality of clients.