VMware recently released a whitepaper showing the performance scalability of Exchange 2007 on VMware vSphere. This paper shows that vSphere 4.0 achieves excellent performance and scalability both with regards to scale up (adding more vCPUs) and scale out (adding more VMs). The results indicate that vSphere can easily support 4,000 heavy Exchange users with a single 8 vCPU VM or 8,000 heavy Exchange users with multiples of either 2 or 4 vCPU VMs. While supporting these high user counts, the latencies of most of our virtualized Exchange configurations are half the recommended threshold (500 ms) with little overhead compared to physical.
Even the largest configuration, which supports 8,000 Heavy users with 16 vCPUs on an 8-way server, provides outstanding user experience. For our 8,000 heavy user mailbox configuration, the 95th Percentile Send Mail latency Is 273 ms with eight 2 vCPU VMs and 304 ms with four 4 vCPU VMs.
95th Percentile Send Mail Latency (2 vCPU VM vs. 4 vCPU VM)
In addition to these low latencies, this paper also shows that the 8,000 mailbox configuration consumes less than 60% of host CPU resources, which leaves room for further user growth and further consolidation. In addition, the paper shows that ESX provides consistent performance across all consolidated virtual machines. For example, the response times of the Exchange transactions in the eight 2 vCPU configuration were within 2% of each other. For more information on this research, read the full paper: Microsoft Exchange Server 2007 Performance on VMware vSphere.