Abstract: A technique for handling tape back-up data storage systems for use with a data processing system, wherein a single tape driver interface unit has a process controller for controlling access to an array of tape drive units and data storage tapes. Data is transmitted from a host unit to the interface unit via a first small computer system interface (SCSI) bus and is written into first storage regions of the tape via a second SCSI bus and is read from the tape via the second SCSI bus, the interface unit and the first SCSI bus to the host. Parity entries can be determined by the process controller for the data and written into second storage regions of the tapes via the second SCSI bus when operating in a parity mode. Unless a hard error occurs the same data transmitted by the host can be returned from the host.