Disclosed herewith is a scalable disk array controller inter-connection network to be employed for a disk array system in which a plurality of disk array controllers connected to each another are expected to be operated as one disk array controller. The inter-connection network enables such disk array controllers to be added/removed without service interruption while the system reliability is kept as is. Each of the plurality of disk array controllers comprises a channel IF unit; a disk IF unit; a cache memory unit; a shared memory unit; means for connecting the channel IF unit/disk IF unit and the cache memory unit; and means for connecting the channel IF unit/disk IF unit and the shared memory unit. The inter-connection network comprises a plurality of switches to be increased in a scalable manner. Each of the switches is inter-connected with other switches with use of a redundant path having a separated physical route. In addition, each of the switches has an output destination table used to set redundant paths and switches between paths after the inter-connection network is modified due to the addition/removal of the above switches. The disk array controller becomes cost-scalable because the disk array controller units can be added/removed to/from the system as required without service interruption while the system reliability is kept as is.
A shared memory access function providing unit of each of a plurality of host computers of a network device receives an access shared memory request from an application and issues the access shared memory request to an FC switch. An access shared memory request identifying unit of the FC switch determines whether the request from the host computer is an access shared memory request, and if the request is an access shared memory request, a shared memory control unit controls the access to a shared data memory unit based on the access shared memory request.
