Virtual Data Center

Understanding I/O bottlenecks throughout your physical architecture


What to virtualize with Microsoft Exchange

Virtualizing only certain aspects of Microsoft Exchange helps you get the benefits without undermining performance, says an expert.

If you’re considering virtualizing Microsoft Exchange, it’s wise to be skeptical. But when properly designed and tested, the outcome is a smooth-running Exchange environment that offers all of virtualization’s benefits for some Exchange roles.

First, consult Microsoft’s Virtual Machine Support Policy for Exchange Server 2003.Microsoft supports Exchange Server 2003 running on virtual machines (VMs) with the following:

  • Virtual Server 2005 R2 or a later version;
  • Microsoft Exchange Server 2003 Service Pack 2 (SP2) or a later SP version;
  • Microsoft Virtual Server 2005 R2 Virtual Machine Additions installed on the guest OS;
  • Exchange Server 2003 configured as a standalone server, not as part of a Windows cluster;
  • Only the Microsoft Virtual Machine PCI SCSI Controller driver installed as a SCSI driver;
  • The virtual hard disk with the Undo feature not enabled.

Microsoft Exchange 2007 is not supported for virtualization, but with the upcoming release of Windows Server2008’s Hyper-V, full support from Microsoft is imminent. As far as VMware Inc’s offerings, Microsoft will support Exchange on Vmware only for Microsoft Premier support-level customers and with some caveats.

Based on my consulting work with shops that have put Exchange on Vmware ESX Server, I've learned these key dos and don’ts:


  • Do virtualize Outlook Web Access servers.
  • Do virtualize SMTP-only servers.
  • Don’t virtualize back-end servers unless you are doing extensive testing with raw disks on VMware. The Mailbox Role is where all the I/O-operations-per second heavy lifting happens. The same applies for Exchange 2007.


  • Virtualize Central Authentication Service (CAS) servers.
  • Virtualize Hub Transport.
  • It is feasible to virtualize Microsoft Internet Security and Acceleration Server 2006 as your application layer proxy.
  • Don't implement a VM's unified messaging (UM) role, which falls flat on its face in VMs.

Getting a jump on virtualizing some aspects of Exchange allows you to consolidate hardware and enjoy the benefits of virtualization without drastically affecting performance. Because Exchange 2007requires 64-bit hardware (and VMs by proxy), many tasks can be performed in RAM that enable Exchange 2007 to scale better than Exchange 2003 in a virtual environment. Many customers that have invested heavily in VMware already have the staff to perform a cost/benefit analysis and take the plunge into production. But proper planning and solid testing procedures are the key to successfully virtualizing Exchange.

About the Author

Dustin Lema is a consultant with BT in North America. He is a VMware Certified Professional and an Active Directory and Microsoft Exchange expert.

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