While many questions arise in server virtualization projects, one that is always asked is, "How many licenses do I need?" Some have resorted to educated guesses while others have had to work through resellers or directly with Microsoft to ensure licensing assessments are correct.
What if you're the one being asked about
To help make accurate licensing assessments, Microsoft now offers the Windows Server Virtualization Calculator. To use the calculator, you just need to know the number of processor sockets (not cores) on each server, and the planned number of virtual machines (VMs) that will run on the server. Once you have this, you can enter the information in the table shown on the page.
For example, suppose that you plan to run 8 VMs on a 4-way server. If you use the blue table, enter "4" in the Number of Processors field and "8" in the # of VMs Per Server field, you will see that the least expensive option is to purchase two Enterprise Server licenses.
To summarize, the virtual machine OS licenses that are included with each Windows edition are:
- Windows Server 2003 Standard -- No additional licenses for VM. The host OS requires a license and each VM requires its own OS license.
- Windows Server 2003 Enterprise -- One license can be applied to a host system and up to four additional VMs on that host.
- Windows Server 2003 Datacenter -- One license can be applied to an unlimited number of VMs on the host. Licensing is per server processor (not core).
The current licensing mode does not just apply to running VMs on Microsoft Virtual Server. You can use any virtualization platform and still use the same licensing calculator to determine your Windows licensing needs.
For more information on applying Windows OS licensing to virtualization, take a look at the following articles:
- Unlimited virtualization rights with Windows Server Datacenter Edition
- Licensing Microsoft Server products with virtual machine technologies
- Licensing server products with virtual machine technologies
What I like most about the calculator is that it gives you the cost numbers for each Windows edition. This makes it very easy to compare each licensing alternative and select the best licensing model for each planned virtualization deployment. I don't know about you, but my brain's math coprocessor doesn't work like it used to, so any help from a calculator is something that I'll gladly accept.
About the author: Chris Wolf is a Microsoft MVP for Windows Server -- File System/Storage and is a MCSE, MCT and CCNA. He's a senior analyst for Burton Group who specializes in the areas of virtualization solutions, high availability, enterprise storage and network infrastructure management. Chris is the author of Virtualization: From the Desktop to the Enterprise (Apress), Troubleshooting Microsoft Technologies (Addison Wesley), and a contributor to the Windows Server 2003 Deployment Kit (Microsoft Press). Reach him at firstname.lastname@example.org.
This was first published in February 2007