Yup, I use gdb also as a calculator

You may want to try this with a live Linux USB key or CD. It varies based on the Hw RAID controller, but most of the time the physical disks that are part of the RAID are visible in Linux (for example with a LSI HW Raid controller). Not as block devices (/dev/sda, ...), but as generic SCSI devices (/dev/sg0, /dev/sg1). It is possible to run the smartctl tool on those directly.

SMART provides a lot of data, some of which is crap :-) but some of which is very useful. In particular, the error log:

# smartctl -l error /dev/sg0

Any disk with a non-empty error log you should consider replacing. Also, always run the short diagnostic tests:

# smartctl -t short /dev/sg0
# [wait 2 minutes]
# smartctl -l selftest /dev/sg0

What the manufacturer's test programs do is *precisely* run the SMART diagnostic test, so save yourself a CD-R. All they do is run the long self test. All SMART-friendly HDDs support the short (1 to 2 minutes) and long (1 to 2 hours) diagnostic tests, the latter doing an exhaustive sector scan. Boot a Linux live CD and type "sudo smartctl -t long /dev/sda", and voila.

A damaged disk cannot pass that test, not unless something is utterly borked with the firmware (*cough* seagate *cough*).