There's only one company that doesn't use Linux for its server virtualization platform. Can you guess which one it is? If you guessed Microsoft, you're correct. Microsoft is a newbie in the virtualization space but wants in and may make significant dents in the already well-established market that is significantly owned by VMware. For Windows-only virtualization, there may be some validity to the switch to Hyper-V.
For the rest of us, who are either too stubborn or too smart to make the shift to Hyper-V, what are our choices? The following is a list of 5 of the main players in Linux-based virtualization. The list is ordered in what I believe to be from most popular/best supported to the least in this area.
1. VMware - I know I give these guys a hard time but when they're so prominently displayed, they must stand up to a bit of criticism. With over 80% market share, VMware is a force to be reckoned with in the virtualization space. VMware has superb support, excellent training, and their products are rock solid. You'll sleep better at night knowing you've got VMware ESX running and the VMware support people at your service in case something happens to go wrong. If you don't know where to start with virtualization, you should type in www.vmware.com to your browser first.
2. Citrix - I admit that I was more than a little disappointed when Citrix bought Xen in 2007 but it seems to have been for the benefit of both companies. Xen was the first true hypervisor software I ever used and I knew that this virtualization style was revolutionary. A lot of commercial services and virtualization derivative products are based on Xen. Xen is a fine tool but needs more refinement, in my opinion, before it's a strong competitor for VMware. Widespread support for Xen just doesn't exist yet but I assume it will as more companies embrace its technology.
3. Virtual Iron - Based on Xen's virtualization technology, Virtual Iron is an up-and-comer in this space. Though I haven't tried their product(s) directly, I hear very good things about them from other virtualization professionals. I'm not qualified to say whether or not they offer anything above what Xen alone offers--that would take some investigation. Perhaps some of you who've tried Virtual Iron can use the comments section to inform me of your experiences.
4. OpenVZ - OpenVZ, Virtuozzo, and Parallels all sprang from the same origin: SWSoft, which is now Parallels, Inc.
These products are all based on operating system-level virtualization or containers. Containers are actually a type of BSD Jail or chroot jail. This is a very efficient and secure type of virtualization where each virtual machine is really just an extension of the existing system. It's a bit hard to explain in such a small space but compared to other types of virtualization, the costs are nil, the performance is native, and the number of virtual machines can reach into the hundreds. The only limitation is that you have to run the same operating system and kernel for all virtual machines.
5. KVM - Kernel-based Virtual Machines are gaining popularity amongst those who are interested in virtualized desktop infrastructure or VDI. KVM is owned and developed by Qumranet--which is now owned by Red Hat. KVM is efficient and fast, fast, fast which is why it's being widely considered for VDI. ElasticHosts cloud computing company also uses it for its commercial offerings. Read more about Red Hat's acquisition of Qumranet in my Red Hat Welcomes the New Age of Virtualization post.
Here you have 5 possibilities for your potential plunge into virtualization--all Linux-based and all offer free products. Do your own research since your own experiences will lead you in the right direction. Please use the comments section below to relay your personal virtualization experiences to me and the other readers.