WVD vs. HSD (Server OS VDA): Which Multi-session to choose?

With the introduction of Windows 10 multi-session, Microsoft has made it possible to launch multiple sessions of a published desktop/apps on Windows 10 for the first time. Where previously you used to leverage Win10 for a single-session model i.e desktop OS VDA or more popularly known as a VDI (Virtual Desktop Infrastructure), now you can use Win10 for a multi-session delivery model which was only possible using a Server OS (terminal services).

Now if you ask me, which of these multi-session models should I use? I’ll go with the classic response, well it depends !! When I say it depends, it depends on a lot of factors like Application compatibility, licensing, user density per machine, product supportability, ROI, etc. Throughout this article, my focus will be to use the Citrix control plane for deploying and managing these multi-session VDAs.

About WVD (Windows Virtual Desktop)

WVD or Windows Virtual Desktop is a succession of Azure RemoteApp and RDmi (Remote desktop modern infrastructure). Both Azure RemoteApp and RDmi were not much successful and Microsoft decided to retire them in the early phases of their launch. Their replacement i.e WVD has been quite an interesting and successful offering from Microsoft. WVD is a special version of Windows 10 which gives Windows10 a multi-session capability. It is also called Windows 10 Enterprise Virtual Desktop (EVD).

How is WVD different from Server OS HSD model?

WVD is similar to Citrix FlexCast model called HSD (hosted shared desktop) as it also allows multiple users to connect to the same desktop. However, there are many differences that become a deciding factor between these two:

1. Operating System: WVD or Win10 multi-session is a desktop OS based model whereas HSD is based on Server OS.
2. Application Compatibility: Multi-session VDA saves you cost by reducing the total resource requirement in your deployment, but application admins and application owners have been quite skeptical when they are asked to move from desktop OS to server OS and check their application compatibility. Though Citrix AppDNA, plays a great role in testing application compatibility, the reluctance from application owners makes the transition from desktop OS delivery model to server OS delivery model quite difficult. With Win10 multi-session this compatibility concern is removed as application owners do not have to worry about the compatibility of their application as it is still running on Win10 and still be able to have multiple users connect. So it’s a win-win situation for both app owners and Citrix consultants/architects/admins.
3. Licensing: HSD needs RDS CALS (client access licenses) along with a Citrix License whereas WVD doesn’t need an RDS license as it is not a Server OS. Perhaps WVD works with O365 E3 or E5 license entitlement. So if you have already got either of E3 or E5 enterprise license for your users, you can deploy WVD on Azure without any extra cost.
4. Platform or Compute Layer: HSD can run both on-premise and on the Azure platform whereas WVD can only run on Azure. It is not possible to deploy and run WVD on-premise or on any other cloud provider’s platform. This is another very important factor to consider when deciding between WVD and HSD.
5. User density per machine: Using Scale testing and some of my recent design and deployment projects, I’ve observed that with the same VM specification and applications on Win10 multi-session VDA and Win Server 2016 VDA, you can accommodate a higher number of users* on Win Server 2016. Two of my recent customers decided to move to Win Server 2016 based VDAs from WVD because of this factor. Though I should also mention that they already had RDS CALS. (*It is recommended that you do a scale testing for your deployment before concluding on the user density from my test results/observation)
6. Citrix Control plane: Microsoft WVD or Win10 multi-session is currently only supported with Citrix Cloud Virtual Apps and Desktop Service or Citrix Virtual Apps and Desktop standard for Azure. You cannot deploy WVD using customer-managed deployment of Citrix Virtual Apps and Desktop (CVAD).

With all the above factors taken into consideration, the choice will be easier as it is not only about performance or cost but also the supportability, compatibility, and licenses. To conclude, with WVD you get all the benefits of the Terminal server minus the Windows Server OS. You get better application compatibility with most of your enterprise applications which is certainly not there with Server OS.