Patent ID: 7664926

Claim:
A storage system comprising a storage device unit constituted by a plurality of disk devices for storing data, and a control unit for controlling input/output said data as requested by a host computer, wherein the control unit configures the disk devices into a plurality of logical volumes each with a logical volume identification number, an emulation slot type, and a logical volume size, the plurality of logical volumes include at least two different emulation slot type volumes, one of said emulation slot type is mainframe type, another of said emulation type is open type, the control unit configures a plurality of pool areas each of which includes some of the logical volumes that have an identical emulation slot type, ones of said plurality of logical volumes included in same pool area has same emulation slot type, the control unit generates a plurality of virtual logical volumes which include at least two emulation slot type volumes, one of said emulation slot type is mainframe type, another of said emulation type is open type, and in response to a write request addressed to the virtual logical volume, the control unit, if no unused storage area available in said one pool areas allocated to the virtual logical volume, selects one of the pool areas has a same emulation slot type as that of said target virtual volume, selects an unused storage area in one of the logical volumes belonging to the selected pool area, and writes the write target data into the selected unused storage area.