LVM locking on HA Cluster

i want to set up a OpenNebula HA cluster and i’m currently trying to figure out how locking is handled on a shared iscsi storage using the lvm datastore. do i need external locking mechanism or does OpenNebula handle everything by itself assuming fencing mechanism are in place to avoid splitbrain situations ? if other locking mechanisms are needed, are there some guides or documentation on how to set them up for OpenNebula ?