I've been playing with this for hours, and have been unable to figure it out. I tried to convert my RAID5 array of 4 active disks and 1 spare to a RAID6 with 5 active disks.
I did this:
mdadm --grow /dev/md4 --raid-devices 5 --level 6
Here is what I have on /dev/md4:
State: active, degraded, Not Started
I try the following commands:
mdadm --manage /dev/md4 --remove /dev/sdh5
mdadm --manage /dev/md4 --add /dev/sdh5
and it just adds it back as a spare. I then try:
mdadm --fail /dev/md4 /dev/sdh5
to see if it will reset any flags, and it says "/dev/sdh5 No Such Device". So, I tried to re-assemble by doing this:
mdadm --stop /dev/md4
mdadm --assemble --update=resync /dev/md4 /dev/sde1 /dev/sdg1 /dev/sdj1 /dev/sdf1 /dev/sdh5
but it tells me that /dev/sde is busy, and then that it has a bad superblock (From what I've read, I'm sure the bad superblock is just because of the "busy" message). I've tried this with the -f option, too, with no luck.
Where should I go from here?