With the release of Citrix XenServer 5.6 Citrix also released a new virtual appliance dedicated to licensing, the License Server VPX. The appliance is available since July 2010, in the 2.5 years the appliance is available only Citrix XenServer is supported.

If you’re company is using VMware vSphere (or Microsoft Hyper-V) you’re unable to use the virtual appliance. Citrix refuses to release an appliance for other hypervisors then their own, let alone supporting other hypervisors. Technically it shouldn’t be too difficult to support other hypervisors (some people tried), they already do for the NetScaler VPX.

Why do you need Citrix License Server VPX?

The Citrix License Server virtual appliance is hosted on a Linux platform which offers one huge benefit: multiple instance can exist in a network with the same hostname. This means you can import the same license file (where the hostname is included) in multiple appliances. When combined with an intelligent load balancer (like the Citrix NetScaler) this offers a great solution for a high available license server.  With a Windows based Citrix License Server you need to rely on VMware HA (or equivalent) to detect a failure, boot the machine on another host and wait for the service to come back (not protecting against logical errors) .

Although most Citrix products can cope with a temporary loss of the Citrix License Server using grace periods, it can be cumbersome when you have non-persistent systems. There are workarounds to deal with this (see CTX131586) but in my opinion its better to have a reliable infrastructure than to use workarounds.

Besides the benefit of improving high availability there are more obvious reasons you might want to consider the virtual appliance. A dedicated virtual appliance requires less maintenance (less patches, lower attack surface), doesn’t cost you a Microsoft Windows license and consumes less resources.

Examples of how to configure a Citrix NetScaler with Citrix License Server VPX are provided by Daniel Ruiz and EZE Training.

In a XenApp world you also need a High Available RDS License Server. In this TechNet article you can read how to achieve this.

Where can I get it?

The Citrix License Server VPX is available as a component of Citrix XenServer Advanced Edition. With Citrix XenServer Advanced, Enterprise and Platinum Editions customers must allocate the product license by using a Citrix License Server.

For the record, it makes sense to offer a virtual appliance that works for Citrix XenServer.

What could be the motivation?

Vendor locking?

Could it be that Citrix is gently trying to push you to use Citrix XenServer? <Dr. Evil Voice> If you want a high available Citrix infrastructure you need our brilliant products, moehahaha! </Dr. Evil Voice> 

Well, Citrix isn’t pushing their XenServer product to VMware or Microsoft customers. Citrix support all major hypervisor for most of their products (XenApp , XenDesktop, NetScaler, etc). They don’t care what hypervisor you run their product on, as long as you use their product

Stealing licenses?

With the Citrix License Server VPX it is easy to have multiple instance issuing license from the same license file. Since each license server is unaware of the existence of other license servers it assumes it can issue all available license, more than the customer is legally allowed to. So by having two license servers you double the licenses issued, install four license servers and you quadruple the licenses, etc.

I honestly don’t  think that any (enterprise) customer wants to be incompliant by stealing licenses from Citrix. If they want to they can do so already (and I won’t tell you how)

Come on Citrix!

So come on Citrix! Why are you stubbornly refusing License Server VPX support for VMware vSphere? Letting us wait more than 2.5 years is ridiculous!