Windows Server 2016, not likely to arrive until the second half of next year, is going to shake up the way Microsoft licenses its server operating system, moving away from per socket licensing to per core. The change was first spotted by Wes Miller who is, for his sins, an expert on Microsoft licensing policies.

Windows Server 2012 introduced a great rationalization in the way Microsoft licensed its server operating system. The two main editions, Standard and Datacenter, had identical features, and differed only in terms of the number of virtual operating system instances they supported. Standard supported two VMs (in addition to the host OS); Datacenter was unlimited. Beyond that, they were identical. The licenses for both editions were sold in two socket units; one license was needed for each pair of sockets a system contained.

Windows Server 2016 makes that simple system less simple. First, it reinstates the functional differences between Standard and Datacenter editions. Datacenter will include additional storage replication capabilities, a new network stack with richer virtualization options, and shielded virtual machines that protect the content of a virtual machine from the administrator of the host operating system. These features won't be found in the Standard edition.

Second, the licensing moves to a per core model. Instead of 2012's two socket license pack, 2016 will use a 2 core pack, with the license cost of each 2016 pack being 1/8th the price of the corresponding 2 socket pack for 2012. Each system running Windows Server 2016 must have a minimum of 8 cores (4 packs) per processor, and a minimum of 16 cores (8 packs) per system.

For systems with up to 4 processors and up to 8 cores per processor, this won't change the overall licensing cost. Above this, however, things get more expensive; although the price for a single processor 10 core system will remain the same, with two or or more sockets populated by 10 core processors, prices will go up; 2 or 4 processors with 10 cores per processor will cost 25 percent more to run Windows Server 2016 than they did 2012.

This change brings Windows Server's licensing in line with SQL Server's; SQL Server 2014 switched to a per core model. So too did BizTalk 2013. Azure is also licensed on the basis of virtual machine cores, rather than sockets. The switch is obviously a reaction to increasing processor core counts and, with it, reduced importance of high socket count systems.

But this isn't a revenue neutral shift; it's going to end up costing some customers more money. This is a particular issue for those organizations that already have Software Assurance agreements that cover systems that were licensed using 2012's socket-based scheme. Microsoft's data sheet describes the way that licenses convert from 2012 to 2016; the number of new per core licenses received will depend on the result of an inventory of their current per socket licenses.