Here's the updated 2008 version of this article: Virtual Servers Update: VMware vs. Microsoft vs. Xen
Server virtualization has become a great tool for the data center, helped by the leading virtual server software vendors literally giving away their product. And as more IT shops consolidate their servers using virtual machines (VMs), they find an active marketplace and plenty of choices for how to implement the concept.
Adoption of server virtualization is accelerating. According to a Forrester Research, survey 51 percent of enterprises are now using or piloting the technology.
Its a powerful notion: take a single computer (a dual core or multi-processor CPU is best), and divvy it up into separate "virtual" machines with their own memory, virtual hardware and drive images, and other resources. It isn't new: IBM has been doing this on its mainframes for more than 30 years, and we've had blade servers for the past five years too. But what is new is that the power of VM can be delivered to the PC platform, and there is a more compelling argument now that Microsofts Virtual PC and EMC's VMware have free versions, along with pre-configured VMs to make setup even easier. EMC offers this page with dozens of different "virtual appliances" that have already been configured for popular Web, database, and other applications servers. Just copy them and youre ready to run something that could have taken hours or days to setup.
Microsoft even offers a virtual disk image that contains XP with Service Pack 2 and IE 6 for those shops that need to run IE 6 and 7 side-by-side. They also offer pre-built images of Exchange, SQL Server, and Windows Server 2003.
The idea is to run multiple operating systems and applications on the same box, making it easier to provision a new server and make more productive use of this hardware, just like our mainframe antecedents used to do in the 1980s. But unlike the mainframe era, having multiple VMs means IT shops can cut the cost of software development and simplify configuration as they deploy new servers. By eliminating the need for particular peripherals or supporting a particular graphics or network card, a VM set-up cuts the time to configure a new server. And now that there is more power available on the PC platform, it makes a case for more consolidation.
"Two years ago, it wouldn't have been possible to handle so much workload in a datacenter. Now we can, thanks to this new virtualization software," says Rene Wienholtz, the CTO of a Germany Web hosting provider called Strato that has deployed these technologies.
The key to successfully using VMs is to make them as cookie-cutter as possible, so that they can be quickly setup and cloned as new virtual servers are needed for the datacenter.
Comparing the alternatives
There are three major VM vendors currently, with others such as VirtualIron.com coming on strong too. EMC's VMware has been around the longest and has the most complex product line, with both free and paid versions. Microsoft purchased its line of virtual servers from Connectix and now offers the product for free, and Xensource.com has an open-source alternative that has both free and paid versions.
Next page: Five tips for choosing virtual servers. Plus: a comparison chart for Xen, Microsoft, and VMware.