My last installment about how Windows Server handles processor cores discussed Windows Server 2008 and Windows Server 2008 R2. Windows Server 2012 is out and the editions available differ somewhat from prior Windows operating system releases. With the editions available, key differences are not regarding features as one might think but actually concern virtualization rights. Both editions support the same amounts of memory, physical processors, and logical processors. This post is for informational purposes only. Please consult the End User License Agreement (EULA) for your product and/or the link at the end of this post for more information.
These two editions contain all the same features. For example, previous Standard editions did not contain Failover Clustering. Therefore, to use that feature it required Enterprise or Datacenter. Enterprise edition for Windows Server 2012 does not exist. You will find that Failover Clustering as well as any other feature you can find in Windows Server 2012 Datacenter also exists with Standard edition. Virtualization and processor licensing are key differentiators.
Client Access Licenses (CALs) remain required for access to Windows Server 2012. Therefore, CAL requirements have not changed. As in the past, CALs must be equivalent or higher in version as compared to the Windows Server version being accessed. Therefore, Windows Server 2012 requires Windows Server 2012 CALS. Licensing requirements for Remote Desktop Services (RDS) and Active Directory Rights Management Service (ADRMS) remain the same and still require appropriate CALs for access.
What is different is what the Windows Server license provides. A single license for either available edition provides use of up to two physical processors. If you have additional physical processors in the same server, simply assign additional licenses for Windows Server 2012 for the edition purchased as needed for the additional set of physical processors. When I say ‘assign’ another license, I might as well say allocate because this is for licensing compliance. Currently you can only register one license key per server. Just make certain you have enough licenses purchased to cover the number of physical processors and for any virtualization needs (discussed in the next section). Remember, each license provides for up to two additional physical processors. The number of cores available per processor is irrelevant. If you have an odd number of physical processors, you can’t purchase server licenses for individual physical processors; they cover up to two. For purposes of example, if you assign four Windows Server 2012 Standard edition licenses to the same server, that server is licensed for use of eight physical processors and as many cores per physical processor as the OS will support.
Standard server licenses provide the ability to host two virtual machines (VMs) on those same two physical processors that the license covers. The same license also provides virtualization rights. Using the above example with four Standard edition licenses, the server is licensed for use of eight physical processors, as many cores as the OS supports, and up to eight VMs. If you have a need to support ten VMs on the same four (physical) processor system, simply assign one more Standard edition license to support ten VMs even though the hardware may only have four physical processors. The number of licenses needed depends on the number of physical processors or VMs to be hosted – whichever number is higher.
A Datacenter license provides the ability to host an unlimited number of VMs on those same two physical processors. However, like a Standard edition license, you need to assign additional Datacenter edition licenses based on the number of physical processors needed. The number of cores per physical processor remains irrelevant other than staying within the bounds of the OS and, of course, what the hardware itself will support. My take on this is that if you are going to be hosting a serious number of VMs on a host with lots of processors and cores, Datacenter is likely the most cost effective path.
Standard Edition may fit some situations. However, Datacenter is obviously more flexible in terms of virtualization rights and is likely a better fit for highly virtualized environments. While with either edition you may assign more licenses, those licenses have to be for the same edition and may not be intermixed. So what can you do if you go with Standard and find out that the future of the server requires more licensing capacity? You could continue to purchase and assign additional Standard edition licenses as applicable. If you have Software Assurance benefits, you may be able to purchase a Step-up to migrate to a Datacenter license for that server.
Windows Server 2012 supports up to 64 physical processors with an upper limit of 640 logical processors. Hyper-V enabled systems have an upper limit of 320 logical processors. Physical cores remain a preferred option in lieu of logical processors from Simultaneous Multithreading (SMT) when physical cores are available.
My thoughts behind writing this post were to help communicate a significant change that affects server deployment planning. The cost of licenses for Standard and Datacenter editions are different to account for the licensing changes. The price per instance appears to have been reduced such that equivalent instances for Windows Server 2012 may be less than Windows Server 2008 R2 Enterprise. Again, this post is not a definitive source for what a license covers, what the terms are, or what all the different options are that are available. A great source for frequently asked questions and other links to related information, please consult the following Windows Server 2012 Licensing and Pricing FAQ document: