we had a 3 hour power outage that affected our whole neighborhood, therefore my server went down too.

luckily i have it connected to a battery backup which after a while gracefully shut down the server. nevertheless after the power was restored, the system complained about one disk in the RAID mirror being dead. funny enough it pointed to another disk after every reboot…

i removed the “dead” disk from the mirror (or better: the disk that it considered dead at that point in time), re-added it and rebuild the mirror … worked :-)