I've got a couple Linux servers running RAID1 using the 3Ware IDE Raid controller (Escalade model 7006-2). I've been very glad I'm running with a mirrored drive. One of these machines, shut down one night with a kernel panic. I was able to bring it back up without any problems, but the RAID array was marked "degraded." The drive on port 0 was out of sync, though the drive appeared to be working OK. Never having had this problem before, I had to do some research. I downloaded the CLI (command line interface) and user manual for the controller. I couldn't get things to work right, however, and had to ask 3Ware (now owned by AMCC) for assistance. Well, it turns out that the user manual is not up-to-date with the software. So, here is the procedure:

# remove the drive from the array
tw_cli maint remove c0 p0
# this is the command that was missing
tw_cli maint rescan c0
# add the drive back in as a spare
tw_cli maint createunit c0 rspare p0
# rebuild the array
tw_cli maint rebuild c0 u0 p0

As it turns out, I may have some bad sectors on this drive. I wonder if I can reformat it remotely and put it back in the array?