Q: Which version of Hyper-V is best for my workloads?

A: There are essentially three ways to acquire Hyper-V technology (excluding Windows 8's client Hyper-V), and all three have exactly the same capabilities and scalability. The only differences between them are the included rights to run Windows Server on guest virtual machines (VMs) on the host.

Note that these rights are for included Windows Server running VMs. It's not a problem to run other OSs that are licensed, and you can even run additional Windows Server VMs, but they would have to be licensed separately.Here are the versions of Hyper-V and the rights they include:

  • Windows Server 2012 Standard - Provides two virtual instance rights for VMs running Windows Server.
  • Windows Server 2012 Datacenter - Provides an unlimited number of virtual instance rights for VMs running Windows Server.
  • Microsoft Hyper-V Server 2012 - Provides no virtual instance rights for VMs running Windows Server (which makes sense because it's free).

Note that these rights are only for VMs running Windows Server OSs. To decide on the version of Hyper-V that makes the most sense, you should look at the use case. For example, here are some use cases:

  • VDI. Creating a virtual desktop infrastructure (VDI) deployment that will have hundreds of VMs running Windows 8 or Windows 7: The VM guest instance rights that are part of Windows Server wouldn't be usable because the VMs aren't running Windows Server. This means the best option is to use Microsoft Hyper-V Server, which is free, then license the client OSs.
  • Private cloud. Deploying a private cloud with lots of VMs running Windows Server OSs that will move between hosts using Live Migration: Use Windows Server Datacenter, which allows an unlimited number of VMs running Windows Server as part of the Datacenter license cost and full mobility of VMs between the servers.
  • Linux. Deploying a Hyper-V environment to run Linux VMs: Like the desktop scenario, the guest VM instance rights for Windows Servers aren't useful here because Linux has its own licensing, and customers would have to license Linux directly. Use the free Microsoft Hyper-V server.
  • Branch office. A company wants to deploy a server in a branch office with two VMs running Windows Server: Use Windows Server 2012 Standard, which includes two guests running Windows Server. If in the future more VMs were required, additional standard licenses could be purchased and "stacked" on one physical server. For example, if you buy two copies of Windows Server Standard you have the right to run four VMs running Windows Server. It's important to note, though, that if you had two Hyper-V servers on a location running Standard you can't split the two VM rights across boxes nor can you move the VMs between the servers when required. Licenses can only be moved every 90 days. Therefore, if there were two virtualization hosts with two VMs on each, but you wanted the ability to be able to move the VMs between the boxes at any time, you would need to license each host for the high-water mark of VMs (i.e., four VMs) which means two Windows Server Standard licenses would be needed for each server! Datacenter quickly becomes the most logical financial purchase as soon as you start to increase the number of VMs and need mobility of VMs between the hosts

Basically the decision to use Microsoft Hyper-V Server vs. Windows Server Standard or Windows Server Datacenter comes down to the number of VMs you want to run with Windows Server running within them. Therefore, the virtual instance rights of the various versions matter. For non-Windows Server VMs, all three options are the same so you should pick the most cost effective.