Patent ID: 7694090

Claim:
A computer system, comprising: a host computer comprising an interface coupled to a storage system through a network, a processor coupled to the interface, and a memory coupled to the processor; and the storage system comprising an interface coupled to the host computer through a communication path, a disk drive that stores data, a controller that controls input and output of data to/from the disk drive, and a memory that stores information, wherein: the disk drive comprises a first area that stores data accessed by the host computer, a second area that stores update data of the data stored in the first area, and a third area that stores a copy of the data stored in the first area; the controller comprises an outputting module that outputs data to the disk drive, a creating module that creates an entry for the update data, a reflecting module that reflects the update data to the third area, and a marker processing module that creates a marker; the outputting module updates the data stored in the first area based on an update request of the data from the host computer; the creating module stores the entry for the update data corresponding to the update request in the second area, the second area comprising a plurality of entries corresponding to update requests from the host computer; the marker processing module creates the marker, the marker containing information of the range in which the data is stored and permission information having a first data state indicating that the data is allowed to be stored in the third area and a second data state indicating that the data is not allowed to be stored in the third area, based on a request of creating the marker from the host computer to store the created marker in the second area; and the reflecting module searches the plurality of entries in the second area for the marker, and when the marker is found, the reflecting module obtains the update data corresponding to the data storing range which is stored prior to the marker and reflects the obtained update data to the third area when the permission information of the marker is in the first data state, and wherein when the marker is not found, the reflecting module does not reflect data to the third area.