The appeal of Citrix licensing: Hypervisors and per-server licenses

While Citrix chooses to license its XenServer technology on a per-server basis, VMware, its main competitor, opts for the counting-CPU-sockets approach.

Editor’s Note: This is the second part of this two-part series. Check out part one: Citrix and the floating anonymous user.

An aspect of Citrix licenses that appeals to me is its approach to hypervisor licensing. In contrast to VMware, Citrix has always licensed its XenServer technology on a per-server basis, whereas its competitor has opted for the counting-CPU-sockets approach.

Recently, VMware started to move its technologies over to a “per-VM” model for licensing. Whether this change will benefit all customers remains to be seen, but it looks likely that customers that have enjoyed very high consolidation ratios of virtual machines (VMs) to host will come off worse as this change filters through its product lineup. That’s somewhat ironic given VMware’s claim to have the best consolidation ratios of all the hypervisor vendors.

It seems to me that this move by VMware is an attempt to make “VM” the unit by which we consume the cloud. It’s no surprise that the company’s solution providers have been on the per-VM model for some time. The rumour is that VMware solution providers may be moved to a per-GB-of-RAM model in the near future.

Citrix licensing remains committed to the per-server model by which you count the number of servers you intend to install XenServer on and then multiply that by the price for the edition you’re using. I like this approach because it doesn’t penalise customers that are going for a large amount of RAM in a host (aren’t they all penalised already by the cost of high-density RAM from the OEMs?), and it rewards customers for gunning for high consolidation ratios. In contrast, I think the VMware per-VM approach actually penalises customers for doing the right thing: trusting their hardware and the hypervisor to be reliable enough to withstand consolidation ratios that might keep some systems administrators awake at night.

The simplicity of Citrix licensing

What I like about this per-server approach from Citrix is its simplicity. I’ve always found the idea of counting the number of sockets completed as a measure of licensing costs somewhat ironic – coming from VMware, the founder of the x86 virtualisation market. VMware’s move to a per-VM licensing model is possibly an embracement of the virtual machine commoditisation. How intriguing it is that the company believes that placing the cost of the object the end consumer is using, perhaps by adopting a per-VM licensing model, will ease the introduction of showback/chargeback and put the brakes on VM sprawl. But, by the same token, it introduces a new level of complexity to pricing new projects.

In contrast, adding up the number of 2U, 4U or blade-enclosures a company possesses offers a clearer link between what a company consumes and how much it will cost. Whether other vendors will follow Citrix’s approach remains to be seen, but given Citrix’s relatively low penetration into VMware’s market share, they may wish to retain this approach to licensing XenServer. 

Rather than take on VMware head-to-head in the server-consolidation space, where Citrix would find lots of intransigent VMware administrators unwilling to look at another vendor, it’s no surprise that Citrix sees a much easier route in data centre virtualisation by coupling its XenApp and XenDesktop technology into bundles that include XenServer.

In contrast, this application-delivery market knows Citrix licensing very well and is likely to have an existing relationship based around the older MetaFrame and Presentation Server platforms. It might make them more receptive to the introduction of virtualisation from Citrix. After all, it’s hard to see how a per-VM model would really work in a virtual desktop environment where folks are trying to get as many virtual desktops on a physical box as possible to drive down the per-VM cost.

Mike Laverick is a professional instructor with 15 years of experience with technologies such as Novell, Windows and Citrix and has been involved with the VMware community since 2003. Laverick is a VMware forum moderator and member of the London VMware User Group Steering Committee. In addition to teaching, Laverick is the owner and author of the virtualisation website and blog RTFM Education, where he publishes free guides and utilities aimed at VMware ESX/VirtualCenter users. In 2009, Laverick received the VMware vExpert award and helped found the Irish and Scottish user groups. He has had books published on VMware Virtual Infrastructure 3, VMware vSphere 4 and VMware Site Recovery Manager.

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