Educational ICT Virtualisation Specialist

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Jump To: Products > Microsoft > Licencing > VDI

Licensing VDI (virtual desktops) based on desktop operating systems


With VDI each user's desktop run on a centralised virtual machine (VM) on a one-to-one basis, i.e. for 50 users, you need (at least) 50 VMs.

Windows 10 EULA prohibits the operating system to be used solely for the use of VDI, even on a dedicated machine:

"Restriction: use the software as server software, for commercial hosting, make the software available for simultaneous use by multiple users over a network, install the software on a server and allow users to access it remotely, or install the software on a device for use only by remote users"

Therefore, you need a Volume Licensing agreement in place. If it is a school and they have a OVS-ES agreement then they are covered (with Software assurance - SA rights). If it is a commercial business they need either:

1) Windows VDA per device licence (4ZF-00014, for Open Value annual cost, 4XF-00014 for OVS) This would be the licence required for Thin Clients without a windows licence

2) Windows Enterprise licence with SA (Software Assurance). This would be the licence required for desktop or laptop machines with an existing licence.(KV3-00491, for Open Value, KV3-00511 for OVS - seems much cheaper).

Open Value Subscription

Open Value Subscription is an annual subscription mechanism for licencing Microsoft software (servers, desktops, Office, etc.). Microsoft describe it as:

[...] designed for businesses with between 2 and 250 computers that are looking to take advantage of the various benefits of Microsoft’s Software Assurance offerings (Like Upgrade protection, Home Use Rights, Spread Payments, eLearning, etc.), in addition to the flexibility of subscribing to Microsoft technology instead of purchasing perpetual licenses, which provides lower up-front costs, flexible license counts per year, and more. It offers the option to subscribe to Licenses with Software Assurance and Upgrades with Software Assurance (Windows Desktop O/S). Offers non-perpetual licenses and is a three year program.

The number of licences depends on the number of Qualified Desktops and is described as CompanyWide. Desktop licencing is done per-device. A Qualified Desktop is defined as:

Any personal desktop computer, portable computer, workstation, or similar device that is used by or for the benefit of a Customer or any Affiliate included in its Enterprise and that meets the minimum requirements for running any of the Enterprise Products. Qualified Desktops do not include: (1) any computer that is designated as a server and not used as a personal computer, (2) Industry Device, or (3) any device running an embedded operating system (e.g. Windows Vista for embedded, Windows XP embedded) that does not access a virtual desktop infrastructure.

Each computer will require 1, 2 or 3 of:

  • Core CAL collection (to give access to server resources)
  • Virtual Desktop licence (either VDA or SA, see later)
  • Microsoft Office licence

If you agree to licence all 3 for each Qualified Desktop (i.e. have Office available on everything), this is described as Platform licencing and the licences are 5% cheaper. If you have fewer Office licences (or not at all), this is Non-Platform licencing; the licences are a bit more expensive, but you can save a lot on expensive Office licences.

In addition to the above, you will need a Remote Desktop Services (RDS) CAL for each device that is accessing a virtual desktop based on a server OS.

Finally, you will need Windows Server licences to cover your infrastructure, e.g. Domain Controllers, File Servers and Citrix XenDesktop delivery controllers.

In order to access a Windows Desktop operating system (e.g. Windows 7 or 10) on your device, you need either:

  • VDA licence: for non-Windows devices such as tablets and thin-clients
  • Windows Upgrade with Software Assurance (SA): for devices which already have Windows on, e.g. an OEM licence

Extended Roaming Rights mean that you do not need a VDA licence for accessing your desktop from a personal device outside the corporate environment. Microsoft word this as:

The primary user of a VDA licensed device at work can access their VDI desktop from any device that is not owned or affiliated with the user’s organization, without the need for an additional Windows VDA license. This enables VDI users to access their secure corporate desktops through an unmanaged device such as a home PC or an Internet kiosk, without the need for a laptop. However, if the user does not have a primary VDA device at work, and needs to access his VDI desktop from a non-corporate device such as a home PC, then that device would need to be covered with a separate Windows VDA license. Roaming rights are only applicable while roaming outside of the corporate domain, hence any device accessing a Windows virtual desktop within the corporate domain needs to be licensed with either Windows Client SA or Windows VDA.
Example of OVS licencing for 8 devices and 2 servers (DC and desktop controller):
  • 8x CoreCAL (W06-01502: CoreCAL ALNG LicSAPk OLV NL 1Y Pltfrm DvcCAL)
  • 8x Office Professional Plus (79P-02338: OfficeProPlus ALNG LicSAPk OLV NL 1Y Pltfrm)
  • 8x Windows Virtual Desktop rights. Any combination of:
    • VDA (4ZF-00002: VDA ALNG SubsVL OLV NL 1Mth AP PerDvc) *
    • Windows Upgrade with SA (CW2-00076: WinEntforSA ALNG UpgrdSAPk OLV NL 1Y Pltfrm)
  • 1x Windows Server Standard (P73-05608: WinSvrStd ALNG LicSAPk OLV NL 1Y AP 2Proc)

N.B. licences marked with * above are monthly, i.e. you will need a quantity of 12 per year.


Desktop-as-a-Service (DaaS), i.e. cloud-hosted desktops

All the above Open Value Subscription licences are only relevant if you are running the virtual desktop on hardware and storage that is entirely dedicated to you. This means you cannot use them to licence virtual desktops hosted on a servers or storage that is shared with anyone else such as you would find in a datacentre. No Microsoft licence model is available that covers Windows Desktop operating systems in a shared environment.

Yes, this is insane.

Therefore, unless you can afford to rent or purchase dedicated hardware in sufficient quantities to give you the desired redundancy, you will be unable to take advantage of desktop as a service (even though it is technically extremely easy).

However, there is one workaround. By using Windows Server to run your virtual desktop instead of a Windows desktop OS, you can side-step the no-shared-hosting restrictions and you do not need VDA/Windows+SA licences. Citrix refer to this as Server VDI. Windows Server Datacenter licences allow you to run unlimited VMs on the hardware, so it is easier to size. You will still need a RDS CAL or VDI Suite for access.

With Server VDI on Citrix XenDesktop there are a few restrictions as the following features are not supported:

  • Personal vDisks
  • Hosted applications
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Page last modified on December 13, 2018, at 10:35 AM by dneil