In an effort to clean up from a software bug in md, I marked half of a RAID (/dev/sda1 and /dev/sdb1 in RAID1) as faulty using:
mdadm /dev/md2 --fail /dev/sdb1 mdadm /dev/md2 --remove /dev/sdb1
But now I want to use the "failed" half instead. i.e. instead of using
/dev/sda1, I want to use
/dev/sdb1, but mdadm refuses to bring it online:
mdadm --stop /dev/md2 mdadm -A /dev/md2 /dev/sdb1 --run --force
This fails, as it considers
/dev/sdb1 a "spare" and not an actual member of the array any more.