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VMware Vs. Xen Smackdown!

It's a question increasingly asked these days: how does the Xen open source hypervisor compare with VMware's hypervisor, ESX Server, in terms of performance? One big reason it's asked is because of Xen's much lower upfront cost -- if it's in the same ballpark as ESX in terms of speed, that could have a big impact on a company's buying decision.

A preliminary answer is that Xen compares favorably in some ways, but in others it falls well short of ESX Server. That, at least, is the verdict of load testing done for the BriForum conference in Amsterdam last October. BriForum is run by Brian Madden, an independent virtualization and application delivery expert with a popular Website.

In the session, available as a video Webcast, Ron Oglesby of GlassHouse explains how Xen Enterprise fared against ESX Server in several different tests on a 1U Dell server. The first was a single VM running Microsoft Terminal Services. The two hypervisors compared well from a performance standpoint in terms of processor and memory utilization; in other words, the hypervisors were about equally efficient.

Things changed, however, when three more VMs, including a file server, Web server and domain controller, were added. The load testing was done by the open source I/O measuring tool iometer. At that point, VMware pulled away dramatically. With multiple workloads, ESX had almost three times the throughput and three times the disk I/O performance as Xen. That substantially better I/O performance led to much quicker response times for ESX, in both reads and writes.

In this analysis, it looks like Xen is a good candidate for lighter virtualization workloads, and VMware is better for heavier usage. Now, that being said, it's worth noting that since Citrix bought XenSource last year, the company has put an awful lot of resources behind developing XenServer (formerly XenSource), including new products for management and application delivery that improve its enterprise worthiness. That includes the just-released XenServer 4.1, with a new per-server price structure that throws down the gauntlet to VMware and its per-socket pricing. XenServer 4.1 has a number of strong upgrades that certainly make it worth a look.

Also note that XenServer is a Citrix-specific product; lots of companies use Xen as their hypervisor and build functionality on top of it, including Novell, Virtual Iron, Sun, Red Hat, Oracle and others. Like Citrix, they aren't selling the hypervisor; rather, they push the management and efficiency of products built on top of it.

In any event, the video is well worth a look, whether or not you agree with the results and analysis.

Posted by Keith Ward on 04/04/2008 at 12:48 PM


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