On 31/10/17 18:11, Wols Lists wrote:

It's possible - I wouldn't know - that the existence of the MBR stops
mdadm looking for a superblock that applies to the whole drive, which
could explain why those drives have disappeared.

Just been digging in the code - function check_raid - I think if you
pass a drive to mdadm it checks the drive for a superblock, and doesn't
look for whether a partition table exists. So I think that's that
explanation blown out the water ... :-(

Cheers,
Wol