The IBM EXP300 expansion cabinet is suitable for SCSI speeds up to 160mbytes/sec. It comes with sufficient connectors, etc. to accomodate connections from two different SCSI cards. You can either operate it as a single bus, or as two independent buses. The ServeRAID resource agent requires that you configure it as a single twin-tailed SCSI bus.
You can read more about it on IBM web site.