Article by Tony Main

VDA subscription for VDI and RDSH

The current licensing strategy from Microsoft has been with us since 2014, so we should be familiar with it. However, as with all things in IT, liberal use of buzzwords, abbreviations and acronyms are casually thrown around, usually to cause confusion rather than answer the question of what licenses do I need? While a guide on all the permutations that the licensing methods could be written, it would rival War and Peace in length, so we will try to condense the viable aspects, specifically on how it relates to thin client computing. We also will only be focussing on the connection between end-point and service, so other licensing requirements will need to be addressed separately.

Types of License

Microsoft required a Virtual Desktop Access (VDA) subscription to be present on all devices that are connecting to a virtualised desktop (VDI). The VDA is not issued as a license file or a paper certificate, in fact it is more of a tax to pay Microsoft to use VDI desktops. The subscription was applied to all devices that did not run a local copy of a Windows OS that was obtained through Microsoft Software Assurance (SA), as an additional annual subscription cost to the VDI implantation. This requirement meant that even Microsoft’s Windows Embedded operating system would require a VDA.  If SA was not being used then even regular Windows required a VDA.

The VDA subscription requirement is not needed if traditional shared desktop from a server is used, which is now called Remote Desktop Session Host (RDSH). This is catered for by Client Access Licenses (Remote Desktop Service RDSCALS or the older Terminal Services based TSCALS) which are installed on the license server service. These are an upfront, one-off cost and is one mitigating factor in keeping the popularity of RDSH implementations.

Microsoft, in 2014, changed this model to help with the cost of VDI. This was to recognise the fact that the VDI solutions now deliver applications as well as desktops and, the good news for thin client vendors, the recognition of some versions of Windows Embedded as a Windows desktop. For these two delivery methods, the VDA is no longer required, however, it is not as simple as that and we will explore this in more depth in the next section.

With the release of Microsoft Server 2016, a “hybrid” desktop option is now available, called Personal Session Desktops, it provides the look and feel of a VDI session, while being hosted from a server rather than from Hyper-V. This option will use RDSCALS rather than a VDA subscription, and was prompted by the need for cloud hosted desktops (specifically on Azure) without providing the access to Hyper-V configuration.

VDA or not?

To remove the need for a VDA subscription requires the use of Microsoft SA. SA includes the rights to VDI from Windows PC’s already covered by SA, and since 2014 some Windows Embedded operating systems can now be included in a company’s SA register. Thin clients that now run Windows Embedded 8.1 Industry Pro and Windows 10 IoT can now access the VDI space without additional subscriptions. Additionally, SA customers have access to Microsoft Windows Thin PC software, and this also includes a VDA subscription.

Windows Embedded Standard 7 (WES7) and Windows Embedded 8 Standard (WE8S) are still not included Unfortunately, if you own the earlier versions of Windows Embedded, or if the organisation is not large enough or cannot justify the use of SA, or if a device which does not run the supported version of Windows Embedded at the endpoint, then a VDA subscription is required. This includes WES7, WE8S, Mac OS X, iOS, Android, Chrome, Linux and Zero Client devices.

So, what does this mean when it comes to a choice of end-point device? Next week we’ll release a series of pro’s and con’s for using Linux or Windows based devices as endpoints, and the VDA subscription costs will be mentioned. The simple answer will come down to money.

If an organisation wishes to us VDI, and they do not use the Microsoft SA, then they have two choices: get SA or pay the VDA. Microsoft usually pitch the price of SA based on the organisation and their requirements, so this is typically a mid-size to enterprise customer.

This article has pointed out the requirements, but has neglected to mention the cost of the subscription. The average annual subscription for VDA is $100 per device. It also would be quite easy to assume that this cost alone would justify using a Windows 10 IoT thin client with SA, however it is not as straightforward as that. Most Windows Embedded devices are initially more expensive, this is partly down to the cost of the Embedded Operating System, but also down to requirement of the local device to run Windows. As a safeguard, vendors are standardising on 4GB of RAM and 64GB of Storage, compared to 2GB and 8Gb for Linux. The biggest “soft” expense that must be considered is the support and management of Windows over Linux based thin clients. This information can best be provided by the thin client vendors, but it is generally accepted that Linux is the least expensive solution to own, from a support perspective.

Desktop as a Service (DaaS)

Another aspect to consider is the use of hosted VDI from a service provider. This was also blighted by the same pitfalls as on-premise VDI, but also had to stipulate a client’s requirements to provide the client Windows licenses as well as pay their subscription charges. This has been extremely messy to deal with, but finally Microsoft in July 2017 released a model for offering virtualisation licenses for Microsoft Certified Service Providers (CSP). Now, a DaaS provider can include the cost of the VDA as well as the Windows OS and application licenses within their service subscription.

There are still differences to the licenses provided to allow for the use of non-Windows based clients, but at least this is now an issue for the service provider to manage, and either pass on or absorb the costs as part of their service offering.


Initially dismissing a Windows Embedded based thin client because of its price, can now be offset for VDI when costing on-premise VDI. The cost saving does still need to be balanced against the additional complexity that Windows devices bring with them in the shape of support and software maintenance. For DaaS, this is a point for negotiation when taking up such a service, so being aware of the costs associated with VDA should be factored into a decision being made about hosted desktops.

To choose a Windows Embedded platform requires careful consideration of the management platform that will assist the deployment and day to day running of the estate. Fortunately, Praim have ThinMan for this purpose, and for existing Windows PCs, Praim Agile extends the look and feel of Windows Embedded to standard copies of Windows 7 and 10.


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