Redundancy for MS Exchange Server

@Praddip: As my understanding, with DAG all emails will be replicated between 2 Exchange servers, am I right? But our email database is really big and we are afraid that we cannot replicate it. Furthermore, we use SAN storage, not the normal way like HDD storage in dedicated server. Can you revise?

@Antzs: If I use DAG with 2 Exchange servers, how many licenses do we need to purchase? Can I use 1 Enterprise license for both servers inside 1 DAG?

If load balancer is out of reach due to the price, you can always use DNS round robin , that's free.

You Just need to set the Mail.domain.com namespace and the Autodiscover.domain.com to two Exchange CAS role servers.

Yeah Agree with Senior IT System Engineer

Depending on your version of Exchange assuming it will be Exchange 2016 , then you can do DAG for Mailboxes with single name space.

https://technet.microsoft.com/en-us/library/dd638129(v=exchg.160).aspx

Exchange Server 2013 standard can also do the IP-less DAG using the single namespace as well.

The Autodiscover entry can now be excluded on the SSL cert, by creating it as SRV record.