Thin clients and HDX 3D Pro support demystified

Recently I was presented with the following case. I was migrating from a Citrix XenDesktop 5.6 environment to a Citrix XenDesktop 7.6 environment. The new environment was running XenDesktop VDI’s with Windows 7 on Citrix XenServer. Because CAD and 3D application support was a requirement, the customer decided to use nVidia grid cards and use HDX 3D Pro.

Everything was running fine in the new XenDesktop 7.6 environment (server wise) and I started testing with thin clients which the customer already had. The thin clients did support HDX 3D Pro according to the manufacturer, so we were good to go. After logging in to the virtual desktop using said thin client, I got the little icon in the task bar telling me that HDX 3D Pro was enabled. But the desktop graphics performance was very poor. It was lagging, slow and was absolutely not fast in response. It felt a lot slower then the XenDesktop 5.6 environment.

Now after investigation I found that these thin clients did not support the H.264 codec fully. Using the HDX monitor I could see that they were using Deep Compression V2. But the cpu of the thin client was being hammered to the max when working on the XenDesktop 7.6 VDI.

The old XenDesktop 5.6 environment was running fine, but the graphics were off course Legacy mode. So the next step now was testing without the nVidia vGPU support in the VDI and enable Legacy mode graphics. That means disable vGPU support in the virtual machine in XenServer, disable desktop composition redirection and enable Legacymode graphics in the Citrix policies. Still the graphics performance was very poor, and HDX monitor showed me that Deep Compression V2 codec was still being used! I was not alone on this, searching the Citrix Forum resulted in:

Contacting Citrix support they eventually told me that I also had to reinstall the VDA agent in the virtual desktop and choose the option not to enable HDX 3D Pro support during installation. When this option is enabled during installation, it is not possible to use Legacymode graphics. This worked, the Windows 7 VDI reverted back to Legacymode graphics and the performance on the thin client was now very good.

So now the next step was to find out what thin client really supports HDX 3D Pro. Not partial support for the H.264 codec, but fully support it so we know for sure that Deep compression V2 codec performance would be good. I found out that manufacturers brand their thin clients with support for HDX 3D Pro or Citrix Certified or Citrix Ready, but they were unclear of the actual performance with HDX 3D Pro. Then I found some information which made clear what the HDX and Certified for Citrix should mean:

 HDX 3D Pro

Check out the website here. Ok, this makes sense. With this new information I started searching for thin clients which are HDX 3D Pro Verified and with this feature enabled. Searching the Citrix Ready Marketplace I found a list of thin clients which were fully certified for HDX 3D Pro! Check the list here. A few of them were already mentioned in a Citrix Forum post here (mentioned earlier).

So this is something that is a little bit of a grey area. Looks like thin clients enabled for HDX 3D Pro does not mean automatically a good performance in the VDI where HDX 3D Pro is a requirement. You have to test, make sure, and then re-test. Otherwise you and your customer will end up with very disappointing results, making you and Citrix look bad while it is the manufacturers of the thin clients who are to blame in not being utterly clear on what their product do support and what you can expect performance-wise (yes I am looking at you Dell).

This is my experience, and I could be wrong on this off course. What are your thoughts in this?

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Vikash works as a technical consultant for a system integrator in the Netherlands, with over 10 years experience in application and desktop delivery. Virtualization is his passion, and his main focus is design and implementation of Cloud and hybrid environments using Citrix and Microsoft solutions. In addition he has broad interest and knowledge in XenMobile and VMware based solutions.