Abstract: In a cluster storage system, storage areas scattered in a plurality of storage nodes are coupled into a single storage area for access by a host computer. The cluster storage system has a first storage node and a second storage node, each of which has a disk and a control processor for controlling input/output to/from the disk, and a host interface node for connecting the first and second storage nodes to a computer. The first storage node manages a storage area having a first storage area existing in the first storage node and a second storage area existing in the second storage node as a logical device. Upon receipt of an access request having identification information corresponding to the logical device from the computer, the host interface node forwards the access request to the first storage node.