Patent ID: 8677096

Claim:
A system, comprising: a storage system coupled to a host computer, wherein the storage system includes a plurality of physical disks, and a controller for controlling to read/write data from/to the plurality of physical disks; wherein the controller is configured to provide a virtual logical unit (LU) to the host computer, wherein storage pool associated with the virtual LU includes an real LU provided with storage areas of the physical disks, wherein the controller is configured to: allocate in response to receiving a write request, a first real storage area of the real LU to a virtual storage area in the virtual LU, store data related to the write request in the first real storage area, and manage the virtual storage area as an uncompressed virtual storage area, wherein if a proportion of the uncompressed virtual storage area to the virtual LU exceeds some predetermined threshold value, the controller compresses the stored data, allocates a second real storage area of the real LU to the virtual storage area in the virtual LU, stores the compressed data to the second real storage area, and manages the virtual storage area as a compressed virtual storage area.