You may have to ask zentyal about this. Windows Active Directory is a multi-master model. Multi-master replication is a method of database replication which allows data to be stored by a group of computers, and updated by any member of the group. Any change made to any domain controller is automatically replicated to all other domain controllers. This happens automatically and you don't have to do anything to make it happen. So there is no need to cluster windows domain controllers.
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