license windows server 2012 for virtualizationIn my last post, we covered the basics of virtualization rights with Windows Server 2012. Now let’s talk about moving virtual servers from one physical host to another. Can it be done? Yes. What licensing do you need to have in place in order for it to be legal? Well, that’s where it gets tricky.

In a post I wrote last year, I discussed vMotion rights for several Microsoft server products. For most server products, if you have Software Assurance (SA), you can move the license from host to host as you move the VM around. Windows Sever is the exception.

Even if you cover a Windows Server license with SA, you cannot frequently move that license from host to host. You are allowed to move it once every 90 days, but that’s it. So as I said in my post last week, your Windows Server license will be assigned to a certain physical host and it will provide you with certain virtualization rights for that host.

So let’s go back to our question: what licensing do you need to have in place in order to move your Windows Server VMs around? If you can’t move the license around with the VMs, then how do you stay in compliance? The answer is that you will need to license every physical server in your environment for the maximum number of VMs that will be running on that server at any point in time. Let’s go over a couple of examples to help clarify this:

Let’s say you have two servers in your virtual environment and each server has one processor. You know that you are only going to have a few VMs running on these two servers, so you decide to go with Standard licenses.

Question 1: Do you need one license or two?

In this environment, you only have two processors and a single license of Standard covers two processors. So, at a minimum, do you need one license or two to cover these two hosts? If you said one, then you lose 10 points and you need to start over by reading my post from last week again. As I mentioned in that post, a single license covers two processors if and only if they are in the same box. You need a separate license for each separate physical server, even if each server has only one processor.

Question 2: How many Standard licenses will you need for each server?

So you need at least two licenses to cover these two boxes, but will you need any more?  The answer depends on the maximum number of virtual machines that will be running on either of those servers at any point in time. Whatever that number is, that is the number of VMs you need to license that server for. As we discussed in my last post, each Standard license will be assigned to a physical host and each license will give you permission to run two VMs on that host. So if you just have one or two VMs running on each machine, then you will be fine with only two licenses. Just assign one license to each physical server and you’re good to go:

license windows server 2012 for virtualization

But if those VMs are ever going to migrate from one host to another, then you’re going to need four licenses — two assigned to each server — since you’ll potentially have three or four servers running on a single machine at some point in time:

license windows server 2012 for virtualization

This may sound counter-intuitive, but you will need a total of four Standard licenses to cover this small environment of two VMs. The reason for this is that the Windows Server licenses get assigned to a physical host, not the VMs, so the licenses cannot be moved around along with the VMs.

Your other option is to purchase two licenses of Datacenter and assign one to each server. Since Datacenter allows you to run as many VMs as you wish on a licensed server, it doesn’t matter if your VMs get shuffled around. Again, the Datacenter licenses themselves will not move around. The licenses are anchored to a single box, but the VMs can move back and forth until the cows come home since there is no limit to the number of VMs you can have on each box:

license windows server 2012 for virtualization

But, as I mentioned in my last post, the only time it is cost-effective to go with Datacenter licenses is when you have 14 or more VMs. And in case you’re wondering, if you buy a volume license of Datacenter, you have permission to create Standard VMs. In addition, all volume licenses include downgrade rights, so your VMs could be Windows Server 2012 or Windows Server 2008 machines. You can mix and match the versions and the editions in your virtual environment to meet your needs.

That about covers it!

For more information on this topic, you can check out my previous posts:

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