Patent ID: 8566558

Claim:
A storage apparatus connected to a host requesting data writing, the storage apparatus comprising: one or more storage devices; and a controller configured to allocate a storage area in a page unit to an area of a virtual volume to write the data in response to a request from the host to write the data; wherein when the data, regarding which the host makes the write request include control information and the data excluding the control information are specified data, the controller is configured to release allocation of the page allocated to the area for writing the data; wherein the data are configured from a plurality of data sets, each comprising data units and the control information regarding counter units; wherein the control information comprises data pattern information that indicates whether data in a sub block of a relevant data set have the same data pattern as the data in the sub block of a data set immediately before the relevant data set; and wherein the controller is configured to release allocation, when in a target data set the data excluding the control information are the specified data and the data pattern information included in the control information in the data set immediately before the target data set is ON.