Kvm Server

We don't have a KVM host appliance, although I can highly recommend ProxmoxVE. It is also Debian based (same as TurnKey) and provides both KVM (for full virtualisation) and LXC (for Linux container virtualisation). Similar to TurnKey it is a headless server, but has a powerful and relatively intuitive WebUI, with an even more powerful CLI (if you SSH in).

As an added bonus, you can download TurnKey LXC templates directly from within the WebUI (or manually download ISOs and install to KVM VMs). LXC is a fantastic option for Linux as it piggy backs off the host's kernel. Therefore it uses much less resources that full virtualisation and has minimal overhead. According to Proxmox, the LXC overhead is only about 5%. In my experience, you get pretty much bare metal performance (relative to the resources you allocate). It doesn't have the same degree of separation as KVM, but it's a fair tradeoff IMO.

Proxmox provides a built in local backup facility (for both KVM and LXC) and all TurnKey VMs/containers can still use TKLBAM if you want remote backups and/or migrate data to/from TurnKey servers hosted elsewhere (e.g. a Hub server).

Proxmox is free (as in freedom) software, as well as free (as in beer). But please be aware that there is a nag screen on log in if you don't purchase a subscription. It doesn't affect the functionality, but you may find it a little annoying.

FWIW I installed Promxox at my previous work and there are a few Windows VMs running fine.

As a tip to get maximum performance out of Windows VMs, I suggest adding the KVM drivers for storage and ethernet and adjusting the virtualised hardware accordingly. It's been a while since I did it so I don't , recall exactly how I did it. But IIRC I did the initial install using the default virtualised hardware (which Windows has drivers for). Then stopped the VM, added the KVM virtual storage and ethernet hardware (in addition to original virtualised hardware). I then restarted and installed the KVM drivers into Windows (I forget where I got them from). And it all just worked. I think I then stopped it again and removed the original virtual hardware. Although I suggest that you do a little googling around that first as perhaps there is some new gotchas or a better/easier way. Perhaps Windows now even provide the KVM drivers by default?

Thanks for the reply Jeremy, I need a mix of clients windows and linux so I will have a look at this see if it makes sense to switch.
Paul