See the MPG review of the OWC Thunderbay 4. HIGHLY recommended (MPG has five of them).
OWC tells MPG that most buyers of the OWC Thunderbay 4 RAID edition have not downloaded the free SoftRAID app. Definitely should be done, because the SoftRAID folks are very good about updating for OS changes.
If you haven't installed the SoftRAID engine that comes free with your ThunderBay 4, you're missing out on your drive's maximum performance.
Applicable part numbers start owctb4msrxxx and owctb2sr