The internet is filled with comparisons between OpenVZ and Xen. This does not come as a surprise since these are generally taken the most popular virtualization platforms. However there are alternatives which can be used equally effective. Some alternatives might even prove equal or better than its popular antagonists. The powerful but less often used virtualization platform KVM is one of these alternatives, especially for XEN users. Seeing their functionalities resemble each other there is some direct competition between both.
The big difference between the two is quite apparent. Xen has been around longer and hence has had the chance to mature. It has a supportive community, many free and usable management tools and a good performance. Also since June 2011 Xen has been integrated to mainline linux. While before KVM had the serious advantage of being supported in linux mainline this advantage now seems to be gone. It means that no custom build adoptions need to be done anymore to get linux running as guest in a XEN environment. This seems a big victory for XEN but it might come two years too late.
Even though the advantages mentioned above speak for XEN it seems that KVM is slowly winning popularity*. The big reason for this to happen is the fact that KVM is at a steady pace taking over XEN in performance** . Even the XEN community after redoing tests -and after installing not yet officially available patches- came to the conclusion, although they did not admit it, that KVM slightly outperformed XEN***.
This does not mean that KVM is better than XEN though. Both communities are actively pushing their platforms and continuously innovating. What it does mean is that KVM is now a worthy alternative to XEN and power users and server owners are picking up on this.
What is your opinion about XEN vs KVM?