Abstract: A computer system has a backplane including a SCSI (small computer system interface) bus for connecting a host processor to a number of disk drive units. The bus operates in a conventional manner to set up a connection, until the stage where the initiator selects a target. Then backplane control logic intervenes, and isolates all units on the bus other than the initiator and the target. Isolation is achieved by means of a set of bus switches on the backplane, controlled by the backplane control logic. This ensures that data transfer takes place over a simple one-to-one connection, reducing bus capacitance and reflections. The backplane also includes power switches that can be operated to power down any disk unit while it is being hot-swapped, and LEDs to indicate when it is safe to hot-swap a disk unit.