Abstract: A Buss Interface and Expansion System, which attaches to a SCSI buss provides, means for increasing the number of devices which can be attached to the buss, provides means for data compressing and decompressing data, and means for use by a host computer attached to the SCSI buss for allowing existing SCSI drives to expand their storage capacity. The disclosed system also provides means for enabling an attached drive to mirror another attached drive, means for creating virtual drives out of devices attached to the peripheral computer, and means for using RAID algorithms on groups of drives attached to the peripheral computer. The disclosed system provides the aforereferenced features while requiring only minimal modifications to the software running on a host system. Through use of electronically reprogrammable storage means, the disclosed system can be updated and reprogrammed by the host computer.