From a load balancing viewpoint, Exchange 2016 is very similar to Exchange 2013 with the major change being the consolidation of the CAS and Mailbox roles onto the Mailbox server. The consolidation of the CAS and Mailbox roles is a supported configuration in Exchange 2013 and is one of the deployment scenarios enabled with LoadMaster Exchange templates. The Exchange 2016 reference architecture recommends the use of a Layer 7 load balancer to benefit from the service health awareness.
Load Balancing in Exchange 2016 works as follows.
- A client session connects to the Exchange namespace virtual IP address (VIP) on the load balancer
- The client session is redirected by the load balancer to an available mailbox server in the load balanced pool
- The mailbox server authenticates the request and performs service discovery
- The mailbox server may proxy or redirect the request to another mailbox server hosting the active copy
The Office Web Apps server, which is required to provide uniform document preview and editing in OWA, is not supported for co-location with Exchange 2016. This means that the Office Web Apps Server farm will require its own namespace with session affinity being maintained by the KEMP LoadMaster load balancer.
In a multi-datacentre environment, global server load balancing (GSLB) is recommended to deliver an Exchange 2016 environment in a single namespace.