In "Virtualizing Exchange 2003," October 2006, InstantDoc ID 92983, I covered the benefits of virtualization, Microsoft's support limitations, and running virtual Exchange servers on VMware ESX Server. I also mentioned that, from a Microsoft support perspective, you can safely deploy Exchange Server 2003 Service Pack 2 (SP2) in a virtualized environment running on Microsoft Virtual Server 2005 Release 2 (R2) or later with only one virtual CPU configured for each virtual machine (VM). I'll follow up here by discussing some matters you should consider when deciding whether to run a virtual Exchange environment.

Third-Party Software Support
Most Exchange 2003 servers run third-party software alongside Exchange 2003, such as messaging connectors and antispam and antivirus products. Although Microsoft supports Exchange 2003 SP2 on Virtual Server 2005 R2, you'll need to verify that your thirdparty software supports this configuration. You might find that suppliers haven't adequately tested their products to validate that they work with Microsoft products in a VM environment. You should also check your third-party software licenses to make sure the software runs on VMs. Some companies license their software on a per-system or per-CPU basis, and that type of license doesn't always support VMs.

If you support a complex Exchange organization, it's likely that you use a management framework such as Microsoft Operations Manager (MOM) to monitor your network or software that analyzes data extracted from system-event or message-traffic logs. Although this additional software might work with VMs out of the box, it's equally true that you might have to resolve some support or compatibility problems before your management framework functions as desired in a virtualized environment.

Additional Training Required?
Installing Windows Server 2003 and Exchange 2003 on a standalone server is relatively simple. Doing so in a virtualized environment is more complex because of the additional layer of interaction between physical and virtual components. Therefore, you'll probably need training to help you understand the technology that lets virtualization software support multiple virtual servers. For example, you'll need to know how to recover from outages that might require replacing and reconfiguring a physical and virtual server or apply software patches to physical and virtual servers. In a nutshell, you'll need to be able to work with virtual servers as easily as you work with standalone servers today.

Small-Scale Virtualization
You can start learning about virtualization technology by using a virtual server that hosts a small amount of user data. For example, you might migrate a single, large multi-CPU Windows server that hosts a number of domain controllers (DCs) or Global Catalogs (GCs) to a virtual server to distribute the load generated by high-demand Active Directory (AD) applications such as Exchange. Or you might want to run some of Windows infrastructure components, such as DHCP servers, on virtual servers. If you want to deploy some element of Exchange on VMs, choose servers that host messaging connectors rather than mailboxes or Exchange front-end protocol servers. Since mailbox and front-end server roles don't hold much user data on the server, if problems arise on these servers, you can move them from the virtualized environment back to a physical server and avoid an immediate service impact on end users.

Using VMs to Test Exchange 2007
Microsoft released Exchange Server 2007 Beta 2 for general testing in July. Many customers plan to use a VM to test the beta version to avoid affecting their production Exchange 2003 servers and because virtual servers are less costly than physical servers.

To test Exchange 2007, you'll need a 64-bit virtualized environment because Exchange 2007 runs exclusively on 64-bit servers, although Exchange 2007 doesn't run on the 64-bit Intel Architecture platform. Currently, you can run a 32-bit version of Exchange 2007 Beta 2 software to test this application alongside Exchange 2003, but eventually you'll need a 64-bit virtualized environment if you want to put Exchange 2007 virtual servers into production.

Exchange 2007 on a VM might more easily cope with storage demands than Exchange 2003 because Exchange 2007's design trades memory for I/O, so Exchange 2007 should run better on systems with reduced I/O capacity. However, it will take time for users to test Exchange 2007 in different environments before you'll start seeing firm recommendations for deploying virtual Exchange 2007 mailbox servers.

Ready for Prime Time?
Virtualization is an important IT trend and will no doubt have a major influence on hardware and software design over the next few years. Because of the complexity involved with deploying and supporting a virtualized environment, it's hard to make a strong case today for using virtual Exchange servers, especially mailbox servers. However, as virtualization software matures and more people gain experience with running and supporting virtualized environments, I foresee many companies successfully deploying and using virtual Exchange mailbox servers in a production environment.