The enclosure came from PC-pitstop. The drives appear to be running
very cool. Also, the problem happened at a time when they were largely
inactive. If it were heat / power I would suspect that when I loaded
the data to the drives would have been a more likely time for failure.

I am just about ready to move the drives internal (scrapping the
housing / psu and cables) but I really liked the idea that the drives
(and their inherent heat) were kept out of the chassis.

Someone suggested the drives might be taking too long on an error and
timing out the controller, but these drives have TLER and thus aren't
supposed to cause such problems for RAID.

-Jeff