I was discussing Xensource with a potential client a few weeks ago, and was fairly surprised when they pulled out a performance comparison of VMWare and Xen, which showed VMware massively outperforming Xen in several tests. On further inspection, it was fairly obvious that VMWare’s tests used the open-source version of Xen, and were running windows based tests on it. This might be a fairly typical enterprise environment, but they weren’t really playing a fair game – Xensource’s product range include a PV driver set for windows which drastically improves performance. This driverset isn’t available under the open source version of Xen.
The comparison the client had been given also had some other data included, some of which was misleading, and some of which was just plain wrong. It included statements such as ‘Xen does not support live migration’ when it does (and what’s more, the open source version supports it natively, so it’s not a bolt-on to the product), and a point stating that Xen had no management consoles available on one page, and a price comparison of VMware, Xensource and VirtualIron on the next. Xensource provide a commercial management console for Xen. Huh.
After a bit of digging, I found the original VMware published report that this comparison was drawn from. Yes, VMware didn’t run a fair test, and yes, given that unfair test, Windows under VMWare ESX massively outperforms Xen in some areas, primarily I/O related.
We mentioned that this report was being circulated to Xensource at about that time. They must have been getting the same heads-up elsewhere, because within a few days of that they had published a performance comparison of Xen Enterprise and VMWare ESX themselves, and even gotten approval from VMWare to publish it! Roger Klorese links to the report from his blog. The report is here.
The report shows that the gap between VMWare ESX and Xen Enterprise performance is negligble in most cases, and Xen Enterprise outperforms VMWare ESX considerably in some areas. It’s definitely a much closer race than VMWare’s report would have you believe.