Over the last couple of days, there have been a small but growing number of errors reported on disk one of my NAS (RAID 1, so mirrored). I wasn’t too concerned, as it didn’t look calamitous. I had a spare disk somewhere, I would fix it when I had a moment. Meanwhile the NAS device worked around the errors.
Last night, the RAID simply shut down, and it wouldn’t come up again this morning. I unplugged the faulty drive, and tried starting the NAS with the single good drive, nothing.