Q. If I add a new writable Windows Server 2008 domain controller (DC) to a hub location, do I need to do anything to redistribute replication connections to my Read Only Domain Controllers (RODCs) in spoke/hub locations?

A. No. Read Only Domains Controllers (RODCs) are unique among DCs in that they automatically rebalance and redistribute themselves without any manual action in Server 2008. (In Windows Server 2003, you have to use a tool, such as Adlb, to rebalance replication.) When a new writable DC is added to a hub location, the RODCs learn about the new DC's existence via the configuration partition replication. The next time the RODC Knowledge Consistency Checker process runs, it decides if it should modify its replication partner by using an algorithm based on probabilistic load-balancing.

All this essentially means that after all RODCs have run the algorithm, the RODC replication connections should be balanced evenly between all the writable DC's in the hub. For example, if you had two DCs in a hub and you added a third, then a third of the RODCs would decide to change replication sources, thus evenly distributing the replication connections.

The same process works in reverse. If you remove a writable DC, then the RODCs that were replicating from it will evenly redistribute themselves between the remaining writable DCs in the hub.

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