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Exchange 2010 - DAG & Server Roles

gunschee asked
Our network has an Exchange 2010 installation ultilizing a DAG.  The DAG has one DB copied between three servers.  All three of these same servers host Mailbox, Transport, and the CAS roles.

One thing that's not clear to me is the relationship between the Failover Cluster Manager, the DAG, and the non mailbox roles.  Obviosuly the activiation preference and other parameters control which server has the active copy of the DB, but what server has the active CAS and Transport role when NLB or an array is not in play for those roles?

Is if the same server that is currently hosting the active mail DB?
Watch Question

Exchange 2010 no longer uses the cluster resource model for DAG.  A Windows Failover Cluster is used by Exchange, but there are no cluster groups for Exchange.
A windows NLB is also using Windows Failover Cluster  and thats the reason you cannot have WNLB on a mailbox role with a DAG. You should put the CAS on a seperate machine
So the DAG is only responsable for the databases > it is used ony on mailbox roles
If you dont have a CassArray and NLB no one controls the active CAS.  The databases are connected to a specific CAS with this attrubut  RpcClientAccessServer > Get-MailboxDatabase |ft name, *rpc*
When you have a CasArray the RpcClientAccessServer is pointing to it for High Availability
Transport role is by default on High Availability with Shadow Redundancy

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