A storage device control apparatus includes a mounting part and an internal connection part. The mounting part can removably mount channel control unit, each with a host interface controller formed therein for receiving data I/O requests, disk control units, each with a disk interface controller formed therein for performing I/O control of the data to storage volumes storing data in response to the data I/O requests, cache memory units, each with a memory formed therein for storing the data, and storage control units, each with the host interface controller, the disk interface controller, and the memory formed therein. The internal connection part connects the channel control units, the disk control units, the cache memory units, and the storage control units in a communicable manner.