Desktop Virtualisation Desktop virtualisation presents many technical choices but they could turn out to be the easy bit. Licensing the software is where it all gets difficult, especially when the software is Microsoft Windows.
The problem is that Windows licensing is based on the assumption that you install software on hardware, but virtualisation abstracts the hardware away.
“Microsoft does not sell a user licence for clients accessing or running Windows. Customers often want to license Windows based on a user model that allows the user the flexibility to gain access from any device,” according to a Gartner report.
The authors think the chances of Microsoft introducing site licensing for Windows OS are “remote”.
So how is Windows licensed in a virtual environment?
If you are doing session virtualisation with Remote Desktop Services (RDS), you are in luck. There is only one instance of Windows running on the server, and all you need is a Windows Server Client Access License (CAL) supplemented either by a RDS CAL, which is a perpetual license, or by Microsoft’s Premium VDI Suite, a subscription that include RDS CALs.
An RDS CAL can be per user or per device, but you cannot mix and match. Per device is great if you have many users sharing a few PCs, and per user is great is you have users with several devices; if you have both, you just have to do the sums.
One for all
That’s session virtualisation. If you want to use a virtual hosted desktop, where all users have their own Windows virtual machine (VM), it gets more difficult and expensive.
You might think that Windows has to be licensed for the VM on the server, but it is not that simple. Each device that accesses that VM has to be licensed.
There are two plausible ways to do this. First, if you have a Windows PC with Software Assurance, Microsoft’s subscription covering upgrades and support, then that PC is covered automatically. Second, if you have a device such as a thin client that does not run Windows natively, you can obtain a Virtual Desktop Access (VDA) licence for that device. This is subscription-only and costs about £68 per device per year.
This is not just for your main thin-client device but for each one you use. Imagine, for example, that you normally access your virtual hosted desktop from a Windows 7 PC. Then you get an Apple iPad and use a remote desktop client to access your Windows virtual desktop. Microsoft requires a VDA license for that iPad to make it legal.
Free to roam
However, if the iPad belongs to you personally, and you are the primary user of another licensed device, then you can use the iPad for free under roaming provisions.
This is just the Windows licence. If you are also using Citrix or VMWare technology, for example, further licences apply.
Few applications are as complex as Windows in licensing arrangements. Adobe, for example, licenses its desktop software per user – not per concurrent user – irrespective of whether it is running locally or on a remote VM or in a session on a terminal server.
"Microsoft's ability to move from per-device licensing will create a cascade of issues"
Microsoft Office, however, has some wrinkles. “Generally only licences obtained through the Microsoft Volume Licensing Program can be deployed to a network server for remote access,” says the company’s guide. In other words, you need a subscription.
Why does Microsoft make it so difficult?
“While the demand is real, we believe Microsoft's ability to move away from per-device licensing for Windows will create a cascade of issues (such as OEM agreements, revenue forecasts and profitability) for which there are no simple solutions,” says Gartner.
The simple solution is to use an alternative operating system – except that for many organisations that would create another “cascade of issues”.
In the meantime, it seems that Microsoft really wants you to have Windows devices and subscription licences if you are heading down the virtual desktop path. ®