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Open source hypervisors on VMware shops’ radars

Respondents in our 2011 Virtualization Decisions survey gave Citrix XenServer and Red Hat KVM a new look.

Hypervisors based on open source code will get new consideration from users in the next 12 months, according to the results of's 2011 Virtualization Decisions survey.

The primary virtualization platform for a majority (more than 70%) of respondents over the last three years has been a version of VMware’s ESX or ESXi hypervisor. But when respondents were asked, “If you're considering an alternative to your primary virtualization platform, which of the following will you deploy over the next 12 months?” responses over the last three years have shown an uptick in interest in hypervisors whose roots are in open source.

Interest in the commercial Citrix XenServer is on the rise:

  • In 2009, 11.49% responded with XenServer.
  • In 2010, that number was 10.1%.
  • In 2011, that number was 14.42%.

So too, is interest in the Kernel-based Virtual Machine (KVM) and Xen:

  • In 2009, 4.70% responded with Red Hat Xen/KVM.
  • In 2010, a total of 5.8% responded with KVM or Xen.
  • In 2011, 6.13% responded with Red Hat Enterprise Virtualization, another 2.15% responded with Xen, and 0.31% responded with another form of KVM, for a total of 8.59%.

If all flavors of Xen and KVM are combined, open source hypervisors are attracting 23.01% of interest this year, compared with 19.94% who are looking at Microsoft Hyper-V.

A majority (57.24%) of respondents said cost was the leading factor in considering alternatives to VMware.

Good enough is good enough
Users who have deployed Citrix XenServer and Red Hat KVM say the hypervisors may not match VMware feature for feature, but recent versions can support higher-end workloads, and the price is right.

According to Federico Alves, president and CIO for Emerg & Co. Inc., a consultancy and managed services provider in Sunrise, Fla., the $300 subscription price per server per year for Red Hat Enterprise Linux with KVM included was a no-brainer.

As part of his business, Alves hosts memory-intensive voice over IP (VoIP) switching services on eight Dell Poweredge R900 series servers packed with 128 GB of memory each, running a total of about 300 virtual machines (VMs), half of them Linux-based. Licensing vSphere 5 for a pool of a terabyte of memory would have cost close to $30,000 under VMware’s original vRAM pricing. Even with the revised memory guidelines, which only charge for the first 96 GB of RAM in the memory pool, licensing the servers would still have cost $3,495 each for VMware’s Enterprise Plus licensing level.

“Paying the money to VMware to do what I do with their technology would be insane,” Alves said.

Recent versions of Xen, XenServer and KVM have also upped the ante in terms of performance, making them good enough for more demanding workloads in larger shops.

For example, XenServer 6.0, based on the open source Xen 4.1 hypervisor, can now support up to 128 GB of memory per guest and up to 16 virtual CPUs. That’s still not on the level of VMware’s vSphere 5 terabyte of memory per guest and up to 32 vCPUs, but for one financial analysis tool supplier in the Southwest, it was enough to swap out more than 1,000 VMware VMs running on 400 Cisco UCS blades.

“VMware’s management stack is definitely the best of any virtualization offerings,” said the company’s vice president of infrastructure architecture. “But it doesn’t equate to the disproportionate price you pay for it.”

Being less mature than VMware, these hypervisors also still have their kinks to be worked out. Alves said he has experienced bugs with Windows VMs running on KVM in a test lab, which caused them to crash.

“But as soon as Windows virtualization is rock solid [in KVM], I don’t know why anyone would use VMware,” he said.

A mature, varied market
In general, analysts say the increasing interest in new hypervisors indicates a broader range of applications being virtualized.

“As companies explore virtualizing more and varied apps, it makes sense that they would take into account the OS and platform the apps have been optimized for,” said David Bartoletti, senior analyst with the Taneja Group.

Others predict Microsoft’s Hyper-V 3.0 will give it a stronger showing next time around.

“Microsoft is on a long release schedule compared with competitors, and it gets a little stale in people’s minds,” said IDC research manager Gary Chen.

Citrix is refocusing on cloud computing with XenServer 6.0, and Microsoft is just starting to talk about Hyper-V 3.0 and Windows Server 8.

“Other platforms have new releases and are more on people’s minds right now. But I’d expect that to change next year,” Chen said.

Beth Pariseau is a senior news writer for Write to her at

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