The VMware performance team is constantly working to show how virtualizing tier 1 applications on vSphere can provide comparable performance to physical deployments. With the release of vSphere 5 we can now provide up to 32 vCPUs and 1TB of memory per VM! That kind of scale-up capability means there are very few (if any) workloads that we can't accommodate.
When dealing with Exchange 2010 designs there are recommended maximums that should be followed to achieve the best performance. Those recommendations are published by Microsoft on TechNet. For stand-alone mailbox servers the recommended maximum is 12 CPU cores, when working with six core CPUs. For multi-role servers the recommended maximum is 24 CPU cores, again when working with six core CPUs. For those customers that prefer to run very large instances (>8 vCPUs) of Exchange servers vSphere 5 now makes this possible.
In keeping with tradition the VMware performance team has published a whitepaper examining how Exchange 2010 performs on vSphere 5 in terms of scaling up (adding more vCPUs) and scaling out (adding more VMs). This paper shows that vSphere 5 can provide flexibility in deployment while maintaining a positive user experience.
For the full paper see Microsoft Exchange Server 2010 Performance on vSphere 5.
Alex Fontana, Sr. Solutions Architect