As Citrix XenServer becomes more mature and gains wider market exposure, performance comparisons to VMware are being made in a rigorous fashion.
VMware vs. Citrix XenServer
Recently, VMware published a XenApp virtual machine performance comparison between ESX (3.5U3) and XenServer 5.0. Citrite Simon Crosby submitted a response in which he sites third-party test results from the Virutal Reality Check project.
Additional hypervisor configuration tests were performed by the Tolly Group. VMware respected the Tolly Group’s work so much they allowed the results to be published. Neither independent test — VRC’s nor Tolly’s — turned out quite the way VMware’s internal testing did.
These two hypervisor publishers obviously are working under two completely different philosophies. Here is one outsider’s perspective:
VMware vs. XenServer: Different Priorities
VMware focuses on feature set first while performance is secondary. Citrix’s XenServer centers on efficiency and performance first at the potential expense of features.
VMware vs. XenServer: Storage Multipathing
Being closed source had slowed VMware’s ability to bring certain storage capabilities to market.
Storage multipathing is available in VMware ESX but has not been active/active (at least, not for iSCSI) until the recent release of version 4.
The open-source dm-multipath module for XenServer allows for active/active storage multipathing and has been officially supported since Citrix XenServer 5.0.
VMware vs. XenServer: Relative Strengths
Each server virtualization product has own strengths. There are quirks from XenServer that still bother me, such as a lack of support, and interface, for making guest performance improvement changes to Domain 0. VMware has allowed and supported customizations for the service console and guest VMs and provided the interface to do so with relative safety.
I am pleasantly surprised by XenServer’s recent improvements. Not long ago a colleague expressed his immense disappointment in XenServer’s I/O performance. Recently that same individual put his first XenServer installation into production and hasn’t looked back. Progress is being made very rapidly.
VMware vs. XenServer: Product Summary
When in doubt, test — never make assumptions. Maintain an open mind and find out for yourself which products combine to make the best solution for your technical and business needs. Don’t be afraid to ask questions, either. The biggest sins (I can’t say they are the ‘only’ ones) in this industry are to assume without confirmation and to deny the opportunity to obtain more knowledge.
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