On Thu, 30 Dec 2010, James wrote:

Can someone point me in the right direction?
(a) what causes these errors precisely?

dmesg should give you information if this is SATA errors.

(c) are these errors expected in a RAID array that is heavily used?

No.

(d) what kind of errors should I see regarding "read errors" that
*would* indicate an imminent hardware failure?

You should look into the SMART information on the drives using smartctl.

-- 
Mikael Abrahamsson    email: swmike@swm.pp.se