Patent ID: 8521985

Claim:
A storage subsystem configured to be coupled to a host computer, the storage subsystem comprising: a processor; a memory; a virtual volume; and a page volume which includes a plurality of storage media, and which is configured to allocate page physical area of a normal memory to the virtual volume upon receipt of a write request to the virtual volume from the host computer, wherein: the processor is configured to: divide an address space of the virtual volume into a plurality of pages, and classify each of the plurality of pages into one of a plurality of states including at least a first state, a second state and a third state to manage the address space of the virtual volume; further divide a page which is classified into the second state into a plurality of segments to manage the page classified into the second state, wherein a page which is classified into the first state is not divided into a plurality of segments to be managed; and manage a plurality of predetermined pattern data of the memory; the first state is a state in which, as a result of receiving a request for writing write data in a page, a page physical area is allocated to the page from the page volume, and the write data is stored in the page physical area; the second state is a state in which, as a result of receiving a request for writing write data matched with predetermined pattern data in a segment of the page, the predetermined pattern data and the segment are managed, in the memory, by correlating with each other; and the third state is a state in which no page physical area is allocated to a page from the page volume, and the page is not divided into segments to be managed, wherein the processor is further configured to judge whether the write data matches the predetermined pattern data in the case of which a page designated by an address included in the received write request is in one of the second state and the third state, and wherein the processor is further configured to: allocate the page physical area to the page from the page volume in the case of which the page designated by the address included in the write request is in the third state, and the write data does not match the predetermined pattern data; store the write data in the page physical area; and manage the page where the write data has been stored as a page of the first state.