Comment # 1 on bug 921570 from Steffen Hau

I hit the submit button a bit to early.

After enabling multipathd.service on the the spare blade, it also boots to
emergency mode. Disabling multipathd.service and rebooting makes the system
boot again. The same applies to the updated system.

I have no clue why multipathd prevents the system from assembling md2. In
emergency mode I checked "multipath -ll" and "dmsetup ls --tree" and both do
not have the disk devices used for md2 in use.

I'll attach the journalctl -b output both for a failed (multipathd enabled)
boot as well as for a successfull (multipathd disabled) boot. Disabling
multipathd is no option as the system is equipped with a FC LUN from our SAN.