Patent attributes
A first correspondence table indicates a correspondence relation between logical blocks of a first file and physical blocks of a physical storage. A second correspondence table indicates a correspondence relation between logical blocks of a second file and the logical blocks of the first file. An access request receiving section receives an access request for the second file. A block conversion section refers to the second correspondence table, identifies a logical block of the first file associated with the logical block of the second file that is subject to the access request, and then refers to the first correspondence table to identify a physical block of the physical storage associated with the identified logical block of the first file. An accessing section accesses the identified physical block.