ula1The article today in our “VMware or Microsoft?” series is about the best way to licensing Microsoft Windows Server in your virtual environments.

The introduction of server virtualization in the Intel market place changed the way most organizations run their server infrastructure. It has given organizations great agility in that we can now provision new servers in minutes vs. weeks. We can better utilize servers and datacenter space through server server consolidation. One area that has been difficult to understand  is how to properly license Windows Servers in VMs.

I am a technical guy but unfortunately I have had to answer these licensing questions so often that I now know way more than I ever wanted to about licensing. The good news is that the licenses work the same way no matter what virtualization engine you use. VMware, Microsoft, Citrix, etc all follow the same rules for licensing Windows Server in a VM.

vmsDo I need to License my Windows Servers in VMs?

In 2003, when x86 server virtualization first became mainstream, I was often asked if a Windows Server license was needed to run it in a VM. (BTW: yes, it isWinking smile) At that time Microsoft licensing rules had not considered virtualization technology. In fact this has caused one of the biggest current misconceptions. When you move a virtual machine from one physical host to another it is viewed as moving a physical server license. You are allowed to do this once every 90 days. What? Yep. In the old days you would only move your server license when you upgraded your hardware. Most customers didn’t do that more than once every three years. However, in a virtual world you may want to move the VM and then move it back. You would then need a license for that VM on both servers. Ouch – can you say double license.

In our current licensing schemes we now include provisions around VMs. We started that with the release of Server 2008. It still took a bit to understand the best way to license for virtualization. In Matt McSpirit’s blog entry he did a good job of describing the options under Windows Server 2008 licensing.

The current licensing with Windows Server 2012 is pretty easy. There are two versions of Windows Server 2012 available for Enterprise customers.  Standard and Datacenter. (I am ignoring Essentials and Foundation) Technically both standard and datacenter have the same guts. They both have failover clustering, Hyper-v, IIS, etc. They only differ in licensing.

Server Version Licensing
Standard Can run two Virtual Machines for each license
Can only transfer license to another physical server once every 90 days
Datacenter Licensed by Physical Processors
Unlimited Virtual Machines
Can only transfer license to another physical server once every 90 days

For more on the Licensing see:

So the easiest way to license a Multi host Virtual environment is to have Datacenter licenses applied to your physical hosts. This applies to ESXi or Hyper-v. You can then move around VMs all day long and provision as many as you can fit on the box. Licensing in this fashion will also save you money as long as your have a good ratio of consolidation per physical processor. With multi-core CPUs this should be pretty easy to achieve the lowest cost and it is positively the lowest management burden.