You’ve heard of Sisyphus and his punishment at the hands of Zeus right? That Sisyphus would, for all eternity, roll an enchanted boulder to the top of a steep hill, only to see it too heavy for him to crest the hill and roll back down? This part of Greek Mythology is so well-known that we use the idea as a descriptor for tasks we feel are pointless or doomed to failure. We call those tasks, sisyphean.
Apropos of nothing I assure you, this brings me to the topic of my blog post: Microsoft Licensing for VDI.
Quite a bit more often than I might wish it to, I come across questions related to how Microsoft products are licensed in VDI. As a result, I thought I would set down some of my research here, in hopes that it can be helpful to someone out there who might need it.
(Note: It doesn’t matter who the vendor is; a VDI solution follows the same set of rules regardless of who it comes from – be it VMware or Citrix or Microsoft or Someone Else).
Licensing Windows for Use in VDI
Microsoft licenses their OS by device. This means you will need an appropriate license for accessing Windows on each end user device (be it PC/Laptop or Thin/Zero Client) that will access your virtual infrastructure. However, there are two models for obtaining these rights. One for physical PCs and Laptops, and one for Thin/Zero Clients.
Physical PCs and Laptops
For Physical PCs/Laptops, you must have a Windows license with Software Assurance. As of July 2010, the right to access a virtual desktop via Windows became a right obtained via Windows Client Software Assurance (SA). So, if you have a PC that you wish to connect to your VDI solution, and that PC’s Windows installation is covered by a license with SA, you may access a virtual desktop with no additional licensing requirements.
If however you find yourself in the same situation as the previous paragraph, and you do not have SA, you should contact your Microsoft Sales Representative to discuss how you can bring those PCs/Laptops under an active SA agreement.
For Thin Clients and Zero Clients, you cannot use SA as you are required to above for the simple reason that Thin/Zero Clients are not eligible for SA via Microsoft. As a result, you must license your end point devices in this scenario with a license called Virtual Desktop Access (VDA).
VDA is a subscription-based license. It grants the end point it is assigned to rights to access a virtual desktop with any supported Windows desktop OS. To purchase VDA, you have two options.
Option One is the annuity subscription. This, as it sounds, is a yearly subscription. You pay a yearly subscription fee annually for as long as you need the VDA license (or as long as the VDA license exists).
Option Two is the full-pay subscription. This option allows you to pay for the VDA license for three years, upfront.
Microsoft, in my opinion, doesn’t do much in the way of multi-year discounting here, so the primary decision is around budget cycles and how your organization prefers to pay for on-going software costs.
Licensing Microsoft Office in VDI
Similar to Windows licensing, Microsoft Office is licensed by device. So, just as above, you must have a license of Microsoft Office for each device that will access one or more titles of the Office Suite.
This particular requirement can be a real frustration for VDI Administrators when they attempt to control who in their organization has rights to access certain applications.
There is a reasonable logic that would say “I have 100 copies of Microsoft Office. I have virtualized Microsoft Office, and will meter its use to 100 (or less) concurrent connections by assigning the application to a 100 VM pool. This will keep me compliant.”
However, if those 100 VMs can be accessed from more than 100 end points devices, then compliance will potentially be compromised. For those organizations with the same number of devices as users, all is well. But if, like so many organizations, the number of VDI end points is greater than the number of VDI users, and those users access those devices, you will be out of compliance once the number of devices used to access Office exceeds the number of licenses owned.
In two words, the takeaway is that Microsoft licenses Windows and Office by device. Starting there, you can then decide which path to take for Windows depending on the type of device, and can work out your delivery scenarios for Office to those devices and remain in compliance. And, standard caveat, if you are still unsure and want a sanity check, hit up your Microsoft resource for assistance.
This guide is probably the most helpful one I’ve seen in detailing out how to license properly for VDI. What I’ve written above around Windows is little more than a summary of this guide (and hopefully a little clearer due to brevity).
For information on Microsoft Office Volume Licensing, please see this PDF. Page 2 notes that Office is licensed per device, and gives further guidance on scenarios, etc.