My thoughts and delusions, in blog form.
mdadm
cat /proc/mdstat
mdadm -E /dev/sda2
mdadm –detail –scan
mdadm –detail /dev/md0
mdadm –add /dev/md0 /dev/sda2
To switch a raid array from read-only mode:
mdadm --readwrite /dev/md0
cat /proc/mdstat
mdadm -E /dev/sda2
mdadm –detail –scan
mdadm –detail /dev/md0
mdadm –add /dev/md0 /dev/sda2
To switch a raid array from read-only mode:
mdadm --readwrite /dev/md0