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Server virtualization: Three top methods, plus pros and cons

Currently, there are three main styles of server virtualization, and each has its benefits and drawbacks, according to open source consultant and author Bernard Golden, a presenter at the Red Hat Summit, happening right now in San Diego.

His lowdown on the three ways to virtualize provides a handy guide to the options today. Following his list, I offer some links to definitions, how-tos, tips and news about each method.

By the way, besides being a resident expert on and Golden is president of Navica Inc., an open source consulting firm, and author of the new book, “Virtualization for Dummies”. Check out his views on server hardware for virtualization in this post.

Here are the top three ways to virtualize:

Virtualization style: Operating system (OS) “container” emulation
Examples: Solaris Containers; SWsoft
Pros: Efficient; does not require additional software
Cons: Isolation; dependent upon OS; limits version choice within guest OS types

Virtualization style: Hardware emulation
Examples: VMware Server; Microsoft Virtual Server
Pros: Relatively easy to install and use; true isolation of OS instances
Cons: Less efficient than paravirtualization

Virtualization style: Paravirtualization
Examples: Xen, VMware ESX, Microsoft Longhorn virtualization
Pros: High herformance; true Isolation of OS instances
Cons: Extra software layer; complex to install and administer

Don’t expect these ways and means to remain fixed in time. In five years, all operating systems will be virtualized, simplifying every aspect of server virtualization from planning to upgrades, Golden predicts. Even better, built-in operating system virtualization will make it very difficult for application software vendors to respond to every helpdesk call by blaming the VM.

For more information on the three top ways deploy server virtualization, check out these resources:

For an overview, read Alessandro Perilli’s analysis of virtualization vendor strategies.

Here’s some info on OS container emulation:
IBM DB2 runs on SWsoft Virtuozzo virtualization; Virtuozzo sidesteps Windows Server costs; Sun boots Unix partitioning on Solaris; and Sun commits to Xen.

Get the scoop on hardware emulation: VMware Server on Linux: Installation through management; Optimizing Microsoft Virtual Server 2005; and emulation defined.

For more on paravirtualization, go to: Paravirtualization with Xen; Xen defined; How-to: VMware ESX, Linux virtual machines and read-only file systems; and Virtualization in Red Hat Enterprise Linux 5.

Which style of virtualization do you use? What questions would you like to ask our resident expert, Bernard Golden, about server virtualization strategies? Tell all by commenting on this post or writing to me at

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Interesting analysis. The worlds leading Operating System supplier is unable to provide a scalable solution for consolidation, so produces it's own Virtualisation products, and partners with others who do similarly. This strategy allows the manufacturer to sell multiple copies of it's 32bit operating system to be run "virtually", thus maintaining it's OS sales volume revenues. All other manufacturers 64bit operating systems are capable of running multiple applications, some more than others, but only requiring a single OS to achieve the required server consolidation. Now consider that original manufacturer, when they finally develop and stabilise a 64 bit scalable operating system, capable of safely & securely running multiple applications, they will be selling this 64bit OS based on that premise; so Virtualisation will be an anathema to their sales pitch, ie that their single OS is all you need to buy, to consolidate, save on licensing costs, and of course above all simplify by abandoning the complex world of Virtualisation in favour of the simple world of a single, multiple application capable world of the 64bit OS. I predict the exact opposite of your prophesy! OS Virtualisation will vanish, well in truth it will go back to the geek world it came from and will not be considered for Production systems, because it breaks all the KISS rules about keeping it simple. Not to mention that Virtualisation is vastly less efficient than a single OS, and Power Consumption is the BIG thing now, not throwing Moores Law (cheap ever more capable commodity hardware) at the problem. I'll get back to you in 3 years and we'll see who was right! Colin