resinch a dieing disk or add new disk & resinch?

Seatools crashed into a DOS line, not sure why. The pc did not die like the first time around (this PC has not been booted fo 6 months, and it was "temperamental" but that was mostly an OS issue).

I am confused about your advice. You mean that I should reboot the NAS as it is now (HD1 removed as it is been tested, HD2 and HD 3 in place), let it "rebuild" the Volume, then add Disk 4..?

Starting testing with Victoria 4.6b (lots of buttons which I would not know how to use :-( )
SMART Monitor says "Good"
The "Test Button seem to be doing a Surface test, which isn't what I think I need right now. Exiting Victoria

HD Tune 2.55
Health = OK
Error Scan (quick) = OK, (no Block damage)
Benchmarking (do I need this? anyway..)
Transfer rate
Minimum = 116.2 MB/sec
Maximum = 121.6 MB/sec
Average = GRRR pc died again, before I could read the average
Access Time
Burst Rate