Mind the gap #Windows Server 2012 R2by ps
For changes in your production environment, the difference in licensing Windows Server 2012 R2 can be bluntly boiled down to this: mind the gap between the number of physical processors and the number of virtual machines your servers run.
Especially in profoundly virtualized environments a costly Datacenter Edition may pay off as it allows running an unlimited number of virtual machines on a server even though only two physical processors are covered by this license. In contrast a Standard Edition allows only one virtual machine per processor although as well covering two physical processors. E.g.: if you have a server with two processors and thirteen virtual machines you are in need of only one Datacenter-license in contrast to seven Standard-licenses. Even if you change to four physical processors per server and run thirteen virtual machines there is only the requirement for two Datacenter Editions while you have to buy seven Standard Editions to be on the safe side.
Hence, small changes can make a big difference when it comes to your IT costs. So a little counting and calculating against the background of your migration plans or other change requirements may avoid the common pitfall of “lived cheap is paid dearly”.