A client has purchased 4 Exchange standard licenses... we would like to implement a DAG for their primary site, but also get some site resiliency as well to their secondary site. They are a fairly small exchange environment (<1000 MBX).
The different methods we've come up with:
2x multirole servers at primary site, 2x multirole servers at secondary site <- can't use NLB to load balance CAS/hub
2x MBX servers, 1x CAS/hub at primary site, 1x multirole server at secondary site <- we get site resiliency, a DAG with 2 mailbox servers at the primary site, and only use 4 licenses. But will this work? We don't necessarily need 2x CAS at primary site, load is rather low, we're mainly concerned about the mailbox databases and replicating those offsite. Some downtime to patch the CAS is acceptable (and we get a secondary CAS on next years budget)
1x CAS/hub, 1x MBX at primary site, same at secondary site. <- still only 4 licenses, but lose out on having a secondary mailbox database at the primary datacenter.
I'm leaning towards option 2, but can we use a multirole server at the secondary site? Our performance would still be acceptable during a site failover, even running on a single server, so performance isn't an issue we're dealing with here... we're mainly going after getting our mailbox databases replicated offsite.