DAG and Port Questions
Some of my TOLA customers asked me about DAG configuration some of the questions I thought would be useful for others are below.
1. What port is used for log shipping?
By default, all DAGs use TCP port 64327 for continuous replication. You can modify the DAG to use a different TCP port for replication by using the ReplicationPort parameter of the Set-DatabaseAvailabilityGroup cmdlet. If you modify this port ensure you also change Firewall exceptions.
2. Port Mapping for Exchange 2010 https://technet.microsoft.com/en-us/library/bb331973.aspx
3. Exchange 2010 Storage Calculator - https://msexchangeteam.com/archive/2009/11/09/453117.aspx
4. File Share Witness and Exchange 2010 – File share witness is only needed when you have an even number of members in the DAG. DAGs with an odd number do not use a witness server. The witness can be any computer running Windows Server.
Quorum is maintained at the cluster level. Remember that a quorum is when the majority of members are online and can communicate with each other. The quorum acts as a tie-breaker to avoid “split-brain” syndrome. This occurs when DAG members can’t communicate with each other but are up in running. It’s prevents by always requiring that a majority of the DAG members are available and interacting.
For more information and planning on Site Resilience please refer to this technet article: https://technet.microsoft.com/en-us/library/dd638104.aspx