While trying to correct a DRBD9 problem on PVE 4.2 2-node cluster, I did a drbdmanage -uninit and mangled my setup :) I have only test VM's so I am trying to recover without re-installing.
I rebuilt /var/lib/drbd.d/*.res files by hand
On both servers
# drbdadm create-md vm-100-disk-1
#...