>You could be getting burned by a slow drive.
>Successful retries would not get reported as
>a hard error. You can try swapping drives, one
>position at a time, between the two RAID sets
>and see if the problem moves.

Is there a way to get SMART stats, retry counters, or other
drive-health statistics out through the twe?

Some vendors sell drives specifically tuned to give up early on
error-correction (Reed-Solomon?  Viterbi? trellis? I dunno, these
days), but if der Mouse already has drives, that might not be an
appealing option.

Gordon, do you know if there are effective ways (a' la SCSI
mode-pages) to tell commodity ATA/SATA drives to give up early and
report railure, rather than resorting to rereads and error-correction
attempt?