And we're all Linux users so that probably won't change any time soon. FWIW though we do hope to get images on Azure (which I would assume uses Hyper-V under the hood?) at some point so it is highly desirable to get TurnKey running sweetly on Hyper-V...

My understanding is that to run on Server 2012 (or later) you need to use a "legacy" (type 1?) Hyper-V VM profile (sorry if my terminology is out; like I say I don't really know much about it). If you're using the newer (type 2?) profile then perhaps it's worth trying the "legacy" one?

Secondly it is quite possible that there is some sort of bug (either in Hyper-V or the Debian kernel) that is causing this issue. As we have nothing to do with MS and use the current Debian kernel; bugs in either are essentially out of our control. Having said that it would be nice if we can get it working better for you.

When you say that it's only been since update, I'm assuming you mean from v13.x to v14.x? As I noted above we use the default Debian (Jessie aka 8.x) kernel - currently this one. A quick google suggests that you are not alone in having performance issues with Linux servers on Hyper-V although as per usual there are probably many different causes; many which may not be relevant. A suggest a good starting place would be MS TechNet's "Best Practices for running Linux on Hyper-V". The (very dated looking) "Running Debian in Windows Server's Hyper-V" may also be useful (although it does appear to be more aimed at desktop version of Debian)? If you keep in mind my above comments (about TurnKey being based on Debian) google will probably turn up a ton more suggestions that you will probably be able to judge the relevance of better than me...