Patent ID: 8140800

Claim:
A storage apparatus, comprising: a storage unit including a data storage area for storing data to be accessed by a host system and a free storage area in which NULL is stored; and a control unit for sending and receiving information to and from the host system in response to an access request, the access request including a logical unit number (LUN) and a logical block address (LBA) from the host system, and performing a write access or a read access to the storage unit based on the access request, wherein the control unit has management information for managing a correspondence relationship between a pointer of the data storage area and the LBA and a logical unit, wherein during a write access to the logical unit at a LUN and the LBA corresponding to a first storage area of the data storage area, the control unit sets a second storage area of the free storage area as a new data storage destination that differs from the first storage area, stores data and data identification information including the LUN and the LBA attached to a write access request in the second storage area, changes the pointer corresponding to the logical unit and the LBA from the pointer of the first storage area to the pointer of the second storage area, starts managing the first storage area as the free storage area, and starts managing the second storage area as the data storage area, and wherein during a read access targeting the logical unit and LBA corresponding to the second storage area of the data storage area, the control unit checks whether or not the LUN and the LBA attached to a read access request coincide with the LUN and the LBA included in the data identification information for the second storage area.