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Running open source Xen in VMware environments

Open source Xen can boost Linux server performance in VMware environments, but it also complicates virtualization management. Does open source Xen make sense for your IT shop?

Even if VMware is your primary virtualization platform, open source Xen can be a fit for your organization.

In this article we explore the benefits of using open source Xen in VMware environments, including its effect on Linux server performance. We also consider key management challenges in running a mixed virtual environment.

Paravirtualization: Open source Xen vs. VMware
Before getting into details, let's try to understand the typical virtual infrastructure. Most medium-sized companies standardize on one server operating system, and if other OSes are in place, they are often marginal.

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A company may have 20 Windows servers and just one or two Linux servers, for example. VMware can run on and manage these servers well.

But in larger companies, there are often more Linux servers. And although large numbers of Linux servers will do well in a VMware environment, they do better on open source Xen because of paravirtualization.

In paravirtualization, a virtualized OS can communicate with a hypervisor directly. There is no need to emulate instructions from a guest OS on a host OS, so naturally, a platform that uses paravirtualization is faster.

VMware's latest releases offer paravirtualization, but only at the driver level. If that's all you require, there is no need to add open source Xen to your environment. What VMware cannot do, however, is kernel-level paravirtualization, which allows for more direct communication between a virtualized OS and a hypervisor. If you have many Linux servers that need the best possible performance, the kernel-level paravirtualization capabilities in open source Xen are beneficial.

Virtualization management with open source Xen and VMware
If this scenario applies to you, you may want to add open source Xen to your VMware environment. But take caution: Implementing software that allows you to manage both platforms in the same environment isn't easy.

With Novell's PlateSpin Orchestrate management tool, for example, Novell recommends that you have an on-site consultant install the software. Managing multiple platforms may involve custom scripting as well, so be prepared to pay extra for that.

VMware has won the virtualization battle so far, and in organizations that predominantly virtualize only one OS, there's generally no reason to add open source Xen. It only adds work for an IT department.

But if your company has a large amount of Windows and Linux servers, it may benefit by adding open source Xen. It will improve performance of Linux virtual machines, thanks to kernel-level paravirtualization.

About the expert

Sander van Vugt
Sander van Vugt is an independent trainer and consultant based in the Netherlands. Van Vugt is an expert in Linux high availability, virtualization and performance and has completed several projects that implement all three. He is also the writer of various Linux-related books, such as Beginning the Linux Command Line, Beginning Ubuntu Server Administration and Pro Ubuntu Server Administration.

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