Microsoft made this specific change in order to eliminate the requirement for complex methods of session affinity and improve the end user experience during mailbox failover. When considering the deployment of a load balancer this also allows for a more simplistic layer 4 approach although there is still very much a need for layer 7 load balancing beyond the basic Exchange configuration. Three of these reasons are highlighted and explained below.
- The first and most important reason to use a hardware load balancer with Exchange 2013 is not so subtly disguised within the very name itself in that a load balancer is designed to balance. A load balancer ensures that traffic is distributed between all of the Exchange servers in a manner that is entirely configurable whether that is evenly between all of the systems or on a weight based system. Some of the balancing methods a KEMP LoadMaster is capable of are Weighted Round Robin, Least Connection, and even an Agent-based Adaptive method. All of these methods are not something that Exchange 2013 would be capable of without using a hardware load balancer.
- Another reason to use a hardware load balancer with Exchange 2013 is the high availability of individual Exchange 2013 Client Access services. When using other solutions to direct traffic to the Exchange 2013 Client Access services the determination of what services are available is a very basic up or down determination. If one or any of the services are not functional on a single server that server and its services are considered to be down. With a hardware load balancer these services can be monitored on an individual basis. For example if Outlook Web App is down on one server it can still be utilized for other services such as Exchange ActiveSync. This allows for more efficient use of all of the Exchange roles that have been deployed into the organization.
- A hardware load balancer can offer more than just load balancing for the Exchange 2013 environment. Taking advantage of features such as KEMP’s Edge Security Pack a hardware load balancer can become a multi-purpose appliance. Some of the features that can be offered are pre-authentication and single sign on for the remote Exchange 2013 users providing security to the organization that was once provided by additional products. This allows for coverage of more of the organization’s requirements with a single appliance.
Even though Microsoft has changed the way load balancing Exchange 2013 Client Access services are viewed, the reasons for using a hardware load balancer have not significantly changed over previous Exchange versions. A hardware load balancer is still going to be a critical infrastructure solution when designing a highly available Exchange 2013 environment.