Is it acceptable to install two servers each having CAS and MB roles for HA?
I have one server with CAS and MB roles. If I wanted to add another server for HA, can I just add another server and install both the CAS and MB roles on it then create a CAS NLB and DAG?
January 23rd, 2015 9:52pm

Just found out that WNLB can't be used on a server with a DAG per the link below, however, if I use a hardware load balancer, can I have both roles on both servers?

https://technet.microsoft.com/en-us/library/jj898588(v=exchg.150).aspx

WNLB can't be used on Exchange servers where mailbox DAGs are also being used because WNLB is incompatible with Windows failover clustering. If you're using an Exchange 2013 DAG and you want to use WNLB, you need to have the Client Access server role and the Mailbox server role running on separate servers.

  • Proposed as answer by Allen_WangJF Monday, January 26, 2015 9:53 AM
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January 23rd, 2015 10:24pm

Hi Truwarrior,

As you mentioned, if you plan to deploy multi-role Exchange 2013 servers with both DAG protected mailbox databases and load balanced/highly available CAS server service, you cannot use WNLB due to Windows Failover Cluster (WFC) and WNLB hardware sharing conflicts.

Theres no limitation about hardware load balance for Exchange server role, I find an similar thread about your question, for your reference:
https://social.technet.microsoft.com/Forums/exchange/en-US/35d5bfac-f1d7-48c5-ac68-e9568016346d/exchange-2010-ht-and-cas-and-mailbox-ha-on-2-servers

Best Regards,
Allen Wang

February 1st, 2015 9:34pm

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