Tips for Virtualizing Microsoft Exchange on VMware

E-mail, as we noted in last week’s blog, remains critical to business functions, and Microsoft Exchange is the most widely used e-mail client in the world. Virtualizing Exchange servers on VMware can improve performance, allow you to consolidate various Exchange server roles, combine mailboxes, and increase flexibility of your Exchange infrastructure, so you can scale up or down as your e-mail loads demand.

You’ll end up with 5-10x less physical hardware and more responsive Exchange, plus you can design your environment for your current workload. No need to guess at your resource utilization 3-5 years down the road—just provision a few more VMs when the time comes.

While virtualization can increase performance (VMware claims a 16 core server with vSphere produced double the throughput as physical hardware), Exchange has its own set of requirements and demands, so take a look at these best practices before you start up the installer in your virtual environment.
 

Virtual CPU for Exchange

You’ll need to add 10% or so to the physical CPU requirements to account for the hypervisor. Your total vCPU number should be less than, or at maximum equal to, the number of cores on the host machine.

Turn on NUMA (non uniform memory access) so ESXi can place vCPUs into a single node, but match the VM vCPU number to the number of nodes. In practice, this works to reduce memory access latency, as each NUMA node has allocated memory that it can quickly access. For large scale deployments, the additional latency of a single VM spanning multiple NUMA nodes may or may not be enough to warrant splitting it into smaller VMs.

Overcommitting vCPU resources is acceptable, but you should be careful about it. A single physical core, with a single vCPU, is able to handle approximately 375 users at 100% utilization.