What was worse was that booting back to 5.6 left most of the raid pairs broken, some still having numbers in the md120 range, and one of the drives with an unrecognizable partition table. I think I can repair everything, but did I miss something about this in release notes somewhere?
I just went through this very scenario yesterday on a recovery box, in the end troubleshooting wasn't worth it so I recreated the sets in c6 and re-populated the data back from the master.
Fortunately, it's my habit to always mount on a reliable means like uuid or forced friendly mpath names and I am glad I did, my md0 became md127 after the first reboot and any attempts to stop and re-assemble with the name I had were quashed at next boot.
Scratched that one upto early adopter woes and called it fixed:)
jlc