A storage device control unit for performing data writing/reading to/from a storage device responding to requests coming from an information processor. The storage device control unit includes: a communications interface section for carrying out communications with the information processor; a storage device interface section for carrying out communications with the storage device; a cache memory section including first memory for storage of data coming and going between the information processor and the storage device; and a connection section for connecting all together the communications interface section, the storage device interface section, and the cache memory section for communications thereamong. The connection section is provided with second memory for storage of data same as the one stored in the first memory. With such a structure, the inner process of the storage device control unit can be effective.