8.4 Virtual Exchange servers

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VMware's^[3] ESX Server is a popular option for server consolidation on Intel systems. The idea is simple. Buy the biggest server you can find and then run software that creates logical partitions that support virtual servers. The software (VMware) runs on top of either Windows or Linux and allows you to install different operating systems and applications to form the virtual servers. Once you have virtual servers going, you can install applications to make the virtual servers productive. In concept, this seems very similar to the way that Windows clusters work. After all, Exchange runs as a virtual server supported by a physical server that is part of the cluster.

Is it a good idea to deploy some very large multi-CPU servers and consolidate smaller Exchange servers onto the system, running each as a virtual server? Different people will give different answers, but, at the end of the day, supportability rather than feasibility will probably influence your decision more.

There is no doubt that you can build Exchange servers (including clusters) on top of a VMware virtual server, so the question of feasibility does not occur. Many companies use VMware to test server operating systems and applications, but they do not necessarily take the next step to deploy the same configuration into production. This is where the question of supportability occurs.

As of mid-2003, Microsoft's position on the subject is clear.^[4] It will only support a problem reported on a virtual server if you can replicate the same problem on a standard server. Microsoft does not include virtual servers in its test procedures, so it is difficult for it to provide support for complex applications such as Exchange and SQL in an environment that it does not test. In addition, most production Exchange servers do not simply run Exchange. Instead, they support other utilities, such as migration tools, messaging connectors, antivirus checkers, backup products, and so on. It would be possible for Microsoft to test and validate Exchange on a virtual server, but including all possible permutations into a test plan for a platform that it does not build is asking a little much.

The answer today is that virtual servers are a good idea for testing complex applications, and they have a role to play for server consolidation projects for simple facilities, such as file and print services. However, until Microsoft fully supports virtual servers without the requirement to replicate problems on standard servers, it is difficult to argue a case to use virtual servers in production. Microsoft's purchase of the Connectix technology (to become the Microsoft Virtual Server product) in early 2003 will generate some interesting scenarios as product groups grapple with the need to support a Microsoft-branded virtual server. Interesting days lie ahead.

Server consolidation is a good idea, and, because many Exchange servers support relatively small user populations, Exchange is definitely a candidate for consolidation. This is especially true since network costs have come down, because it can be cheaper to pay for the increase in bandwidth to bring clients back to a small set of large servers in a datacenter than to keep a set of smaller servers distributed to multiple locations. Early Exchange deployments, those that have run since Exchange 4.0 and 5.0, are specific candidates for consolidation, a project that you might care to undertake in conjunction with a deployment of Outlook 2003 so that you can take advantage of its more efficient network use.

^[3] . www.vmware.com.

^[4] . See Knowledge Base article 273508 for details.

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