Patent ID: 7447832

Claim:
A system for storing data accessed from a host, comprising: a plurality of disk devices, the plurality of disk devices storing data; an Input/Output (I/O) detector, the I/O detector accepting an I/O request to a logical volume from a host, the capacity of said logical volume managed by an operating system (OS) in a host being larger than a capacity of a physical storage area actually allocated to said logical volume; an I/O processor, said I/O processor performing an I/O process according to said I/O request; a capacity controller, the capacity controller allocating a physical storage area to a logical volume, said capacity controller allocating an additional physical storage area to said logical volume according to said I/O request when said I/O detector receives an I/O request to a logical volume whose capacity is larger than a capacity of physical storage area actually allocated to said logical volume; a segment manager, the segment manager managing a storage domain of the logical volume; and a physical and logical address manager, the physical and logical address manager receiving a request from the capacity controller and reserving a free segment in response to the request, wherein if the physical and logical address manager receives a request to connect segment from the capacity controller, the physical and logical address manager connects the reserved segment to the logical volume in response to the connect segment request.