Hi!

After simulating (raidctl -F) a disk failure of a 4 disk raid5 (3 + 1
spare), the spare disk got in 'used_spare' state and the whole raid
was still usable under the 'reconstructing' phase. Fine!

But what's the smooth way (== the system is still usable during that
time) back? 'raidctl -B' did the job, but blocks the whole system for
the complete copyback time! Trying it with 'raidctl -R ...', while the
spare is in use, reconstructed the formerly failed disk smoothly, but
left the spare disk in 'used_spare' state.

If this blocking is not avoidable you have to really care about _when_
doing it with a production server! ;-)

Markus.