Hyper-V Virtual
Hyper-V is Windows Server 2008 R2's built-in virtualization solution. The Hyper-V role allows computers running Windows Server 2008 R2 with processors that support virtualization to host up to 384 virtual machines (VMs). On the Datacenter edition of Windows Server 2008 R2, Hyper-V supports up to 1 TB of physical memory that can be allocated to VM guests. Hyper-V is available on the Standard, Enterprise, and Datacenter editions of Windows Server 2008 R2 in both the typical and server core configurations.
Note: Windows Server 2008 R2 Datacenter edition includes unlimited virtual instance image rights. This means that if you have 1 TB of memory on a computer running the Datacenter edition and can run those 384 virtual machines, you don't need to purchase additional operating system (OS) licenses. Once you host a certain number of VMs, the licensing benefits can save your organization a substantial amount of money.