Patent ID: 8677080

Claim:
A storage apparatus comprising: a physical storage device group; and a controller coupled to a host and the physical storage device group, wherein a virtual volume is provided which is a virtual logical volume to which Thin Provisioning is applied, and which comprises multiple virtual areas, a pool is provided which is based on the physical storage device group, and which comprises multiple actual areas, statuses of an actual area are (1) a first status which indicates that the actual area is already initialized and can be assigned to a virtual area, (2) a second status which indicates that the actual area is already assigned to a virtual area, and (3) a third status which indicates that the actual area cannot be assigned to a virtual area and that initialization, which is a specified data write, is to be performed, wherein the controller is configured to: (a) receive a write command for an unassigned virtual area in the virtual volume from the host and, from the pool with which the virtual volume is associated, assign an actual area in the first status, and change the status of the actual area to the second status; (b) change the status of the actual area assigned to the virtual area to the third status; (c) initialize the actual area in the third status and, if the initialization is completed, change the status of the actual area to the first status, and wherein the controller is configured to limit a total virtual volume capacity which is a total capacity of one or more virtual volumes which are associated with the pool, in accordance with whether the pool comprises an actual area in the third status or not, to a capacity of the pool or smaller.