Exchange Server Sizing Guide

Correctly sizing an Exchange Server design is an essential part of any deployment. Whether the plan is to completely host the infrastructure in house, or to use a hybrid approach via public or private Cloud, proper planning and design is key before any hardware or Cloud services are purchased.

The procedure to follow when designing and sizing an Exchange Server deployment is well understood and tested via numerous Exchange Server 2013 deployments over the last few years. The release of Exchange Server 2016 doesn’t change the procedure in any radical way. There are three changes from the previous release that do need to be noted:

  1. The Client Access Server (CAS) role has been removed. The CAS service now runs as a service on mailbox servers.
  2. The Processor requirements have been increased slightly. But the increase is reflected in the Microsoft supplied role calculator tools that everyone should be using during Exchange Server deployment projects.
  3. The Exchange 2016 reference architecture recommends the use of a Layer 7 load balancer to monitor the health of the Exchange services and route requests accordingly.

Point 3 of this list is fully addressed by deploying KEMP LoadMaster load balancers as part of an Exchange Server deployment. There is a comprehensive load balancer calculator sizing tool to help you choose the optimal load balancer design.

The following diagram outlines the infrastructure of a typical Exchange Server deployment and where load balancers sit in the overall design.
Exchange Server Sizing
The load balancer sizing tool should be used alongside the Microsoft calculators and planning tools as part of the well established design procedure outlined below:

  • Make sure you are up to date with the current best practice information for designing an Exchange Server deployment. A good place to start is with this Microsoft Blog post on designing an Exchange Server 2013 deployment. As outlined above the procedure for Exchange Server 2016 is largely the same as for the previous release.
    Sizing Exchange 2013 Deployments
  • The first step after you are up to speed with current guidelines is to gather all the data you have available on the current messaging system in use. Data such as number of users, number of mail messages sent in a day, month, year. How much storage is used? What anti-virus and anti-SPAM solutions are in place. Projected company employee growth. And so forth. In the unlikely event that no previous messaging system is in place then this stage should be used to estimate the requirements for the future.
  • Next the design team needs to figure out the requirements for the new Exchange Server deployment. Anything that might impact the design of the new infrastructure needs to be considered and documented. Examples include mailbox size and quotas, locations of users and number of Active Directory sites required, where Exchange database copies will be placed, what storage architecture will be best fit, growth plans for the organization, what 3rd party applications will integrate with the Exchange Server solution, and what type of clients will access the system. Increasingly access will be focused on mobile device messaging. Use the Microsoft Exchange Server Role Requirements Calculator as an aid to see the sort of information that is required when planning.
  • Once all the information required to fully populate the Exchange Server Role Requirements Calculator has been collected, then it should be entered into the tool. The more accurate the information entered the better the recommendations the tool will produce.
  • Use the recommendations from the calculator on processors, storage, and other infrastructure to help plan the server deployment you need to meet the messaging needs of your organization. Do you go for a few large servers or more distributed smaller servers? Or do you deploy a hybrid solution with some mailboxes in the Public Cloud on Office 365 with some mailboxes on premise? The route decided will be dependent on your expertise and capacity to host on premise servers. Note that the decision is not final. Cloud provision can be added later. But it’s best to get it as accurate as possible during the initial design.
  • Once a design is agreed then it should be fully documented to list the servers, storage, and other components that will be purchased and deployed. If possible get an independent Exchange design expert to review your choices. Then order infrastructure and start the build and deployment process.

This article only gives a high level overview of the Exchange Server design process. But using the procedure outlined here, and reading in depth at the Microsoft Exchange site, will provide a solid foundation for Exchange Server solution design and sizing.