Massive failure on mine in the last week, sodding parity drive decided to give up the ghost. Okay, no problem, I have a spare WD Red 3TB floating around in case a drive fails, so I'll just use that. Goes through preclear, starts a parity write, fails with errors. WTF? It's a brand new drive!
Turns out the new drive is DOA, so I had to get another new one and start the process all over again. It's the preclear that's the issue, it takes like 30 hours just to do that which is a right pain. Still, all up and running and secured again now, but that's the first drive failure I've had on this system. And of course, now that one has gone you know the others won't be far behind...