Patent ID: 8862805

Claim:
A storage system comprising: a plurality of storage devices, and a storage controller configured to control a set of storage devices among the plurality of storage devices as a RAID group, to manage a plurality of real pages in a pool corresponding to storage space provided by the set of storage devices in the RAID group, to provide a virtual volume including a plurality of virtual pages to a host, to receive a write request indicating an address of the virtual volume for storing write data from the host, to allocate a real page of the plurality of real pages from the pool to a virtual page corresponding to the address of the virtual volume, to manage a number of allocatable real pages in the pool, and to transfer the write data to at least one of the set of storage devices corresponding to the allocated real page; wherein each storage device compresses the write data sent from the storage controller and stores the compressed data in the storage device, wherein each storage device generates compression information based on an amount of compressed data stored in the storage device, wherein each storage device sends the compression information to the storage controller, and wherein the storage controller changes the number of allocatable real pages in the pool based on the compression information sent from the set of storage devices corresponding to the RAID group.