Windows Server 2012 R2 is the successor to Windows Server 2012, Microsoft s enterprise server operating system. Developed under the Windows Server Blue codename, Windows Server 2012 R2 made its official debut in late 2013.
Among its many improvements, Windows Server 2012 R2 includes an enhanced Hyper-V hypervisor (Hyper-V 2012 R2) that provides the ability to compress virtual machines (VMs) during live migrations, automatic reallocation of memory between VMs running Linux as a guest on Hyper-V hosts, remote direct memory access (RDMA) support during live migrations, VM live cloning, and support for shared VHDX files.
Windows Server 2012 R2 was announced on June 3rd, 2013, and a preview release became available for download later that month, on June 24th. Upon its official release, Windows Server 2012 R2 was made available in Standard, Datacenter and Essentials editions.