I don't see how it could matter on which scsi host you would connect both drives, as it's the slowest drive that limits the backup speed and not the controller? The slowest drive is obviously always the tape drive, as I don't even see a tape drive coming close to the speed limit of a fast-scsi host. Correct me if i'm wrong here...
about the cleaning cassette, normally you get a cleaning cassette with your dat drive if you buy it new I guess. At least I did...
Justin