Abstract: A large capacity digital storage system includes five standard 51/4 inch Winchester disk drives, a formatter for each disk drive, and a master controller for coupling to the host computer or data processor. The spindles of the disk drives are rotated in synchronism to improve data handling. Successive bytes of digital information are routed to four of the drives, and the fifth drive has parity check information; and control circuitry is provided so that any one of the five standard drives may be unplugged and replaced without interruption of storage system operation.