Increased adoption of VMware infrastructure and continued performance advances in hardware and software have driven the virtualization of Microsoft Exchange. The current version, Microsoft Exchange Server 2007, is a resource-hungry 64-bit application that has reduced storage demands as compared to previous versions. The increased use of memory and heavier CPU load requires efficient virtualization capabilities to meet customer demands. This paper will detail experiments that demonstrate the efficient performance and scalability of Exchange when running inside a virtual machine on a VMware vSphere™ 4 environment.

The key performance requirements for Exchange virtualization are efficiency of single instance virtualization, uniform and predictable performance in consolidation environments, and fair distribution of resources to multiple virtual machines (VMs). Acceptable single and multiple VM performance is required to maintain a positive user experience and assist virtualization and Exchange administrators with capacity prediction and maintenance. Resource distribution fairness allows administrators to identify performance bottlenecks in a predictable manner. With unfair resource distribution it can be difficult to find and isolate the source of user concerns.

This paper addresses all three of these performance characteristics:

• The performance implications of running the Exchange 2007 Mailbox Server role in a virtual environment versus on a physical system.
• The performance of virtualized Exchange 2007 Mailbox Server role when scaling up (adding vCPUs to a virtual mailbox instance), and scaling out (adding virtual mailbox instances to the host).
• Data showing fair virtual machine management, which provides similar service levels for multiple mailbox roles in a consolidated environment.

Some performance best practice recommendations for the virtualized Exchange environment are also provided.