Patent ID: 8819340

Claim:
A method implemented in a storage system having: a first storage system coupled to a computer; and a second storage system coupled to the first storage system, the second storage system including a plurality of second storage devices, the method comprising: providing, by the first storage system, a thin provisioning logical volume (LU) to the computer: providing, by the second storage system, an external thin provisioning LU to the first storage system; providing pool areas, by the first storage system, which are associated with the thin provisioning LU, including a first pool area mapped to a second region in the external thin provisioning LU; allocating the first pool area to a first region in the thin provisioning LU to store a write data to the first region in the thin provisioning LU from the computer; and allocating at least one of a plurality of external pool areas, which are provided by at least one of the second storage devices, to the second region in the external thin provisioning LU to store the write data to the first region in the thin provisioning LU.