The intricacies of software licensing are often much harder to understand than the technology itself. At least for us technical folks. I think that is because in technology the programmers are constrained by the way stuff works and in licensing the only constraints the creators have is their imagination.

In Server Virtualization there are some often unknown licensing points that can save you money $$$. The main point here is that if you are doing a virtualization farm then use Windows Datacenter. It doesn’t matter what virtualization technology you are using. You assign the Windows Datacenter license to the physical machine and you can run as many Windows Virtual Machines as you can fit on the box.

The Windows Datacenter version provides a lower cost for virtualization because you are licensed to run as many Virtual Servers on top of it as you can fit. It is essentially Windows Enterprise server bits with a different Product Id (PID) required. You license it per physical CPU, at a list price of $2999 each CPU.

Here is a quick breakdown of Windows Server options:

  • Windows Standard – includes a license to run on the host and one virtual machine
  • Windows Enterprise – has more functionality than standard includes a license to run on the physical host and includes 4 licenses for virtual machines
  • Datacenter is 2,999 per CPU list – has the same functionality as Windows Enterprise. You are licensed to run as many VMs as you can fit. Once your server density gets above 4 VMs per CPU this becomes the least expensive way to go. (with 8 VMs per CPU that is $375 list price)

Another point, many miss, is that in a farm where you transfer servers from one host to another you can only transfer the server license once every 90 days. So to use the Live Migration or Vmotion technologies you would need to license each host for the maximum number of servers they will ever run. That means in a 2 node farm where I run 10 VMs on each node and I sometimes move the entire load to the other server for patching. I would need to license 20 servers on each host for a total of 40 licenses. That is even though I never run over 20 concurrent servers. So you need to over licensing by 20 server licenses. Ouch! The Datacenter license covers this scenario.

One other way to lower costs in a virtual environment is to use the System Center Server Management Suite license if you use System Center products to manage your servers. This license includes 5 products: Operations Manager, Configuration Manager, Data Protection Manager, Virtual Machine Manager, and Service Manager. The System Center Server Management Suite Datacenter (SMSD) license covers the host and all Virtual Machines on that host. For more information on this checkout: http://www.microsoft.com/systemcenter/en/us/management-suites.aspx

I hope this post helps you on understanding the options in licensing for your Virtual Farm or your Private Cloud. For lots of “fun” reading on licensing you can check out the licensing briefs at: http://www.microsoft.com/licensing/about-licensing/volume-licensing-briefs.aspx