On 06/08/2011 05:07 AM, Einar S. Idsø wrote:
Hi,
We are considering a transition from OpenVZ to Xen for our web server infrastructure. The primary task performed by the virtual servers is to run a number of Drupal sites with a MySQL backend. The webserver and MySQL servers are on separate virtual hosts. We also have a number of smaller hosts running on the same hardware (a couple of dev-servers, a logging-and-monitoring server, a secondary webserver ++).
From what I have understood, there is very little performance degradation in OpenVZ, also for IO operations, due to the use of isolated containers instead of actual virtualisation. I have also seen tests indicating detrimental IO performance of Xen IO [1]. Despite this, I have found several posters [2] suggesting the use of Xen over OpenVZ when it comes to running Drupal sites.
One of the main arguments against OpenVZ is unpredictable and variable performance because VPS-hosts tend to overbook their host capacitiy. This is not an issue for us since we host our own VPSs on our own hardware so we are in complete control.
So: Is there any reason Xen may be able to outperform OpenVZ for the webserver-setup I have described, or should I just continue to use OpenVZ?
Is your goal absolute best performance (why?), or simply adequate performance?
I wouldn't expect to see Xen outperform OpenVZ. However, if your CPU has has virtualization extensions, I would expect performance to be pretty close between the two.
If you're in need of better performance, I would look into tuning other traditional aspects. Find the bottleneck and alleviate it, same as if VMs were running on bare hw.
That being said, if you're considering Xen, I'd give strong consideration to KVM as well. It appears that the major players (RedHat, Ubuntu) are moving away from Xen toward KVM. http://searchenterpriselinux.techtarget.com/news/1511180/Linux-community-tur...
Cheers, Einar
Sources: [1] http://www.ilsistemista.net/index.php/virtualization/1-virtual-machines-perf... [2] http://2bits.com/articles/hosting-virtualization-openvz-vs-xen-which-is-best...
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