Other World Computing offers this 4-Bay Hardware RAID Thunderbolt 2 Storage Enclosure
, model no. 0G033S2TB0GB, for $497
with free shipping
. That's $196 under the lowest total price we could find for a similar enclosure elsewhere. It features two Thunderbolt 2 ports, hardware-managed RAID, LED and audible alarms on device failures, and is hardware configurable to RAID levels 0, 1, 1E, 5, 10, and JBOD.