Electricity went off hard, was restored about 15 minutes later. During the outage I unplugged TerraBlock. After power up, drive 20 was missing with 51 errors. Rebooted in Safe Mode and as it sequenced each of the 24 drives the blue "HDD" light blinked on every drive except #20 - rebooted again and 20 is still missing.
Can I assume the drive is gone and needs to be replaced or is there some utility to scan and repair?