Since this blog Post Microsoft has Released RPM-Packaged Linux IC 3.1 supporting RHEL 6/6.1 and Centos 6 - making things significantly easier and the in-Kernel Modules continued to mature. expect a another bunch of fixes in 3.2 (the merge windows for 3.1 was too short to get the hv_blkvsc dumped)
Since my last (long ago) post about using Linux on Hyper-V (since I have that at work and have to use that) I can confirm the situation has improved albeit I cannot safely recommend production usage of Linux using th Hyper-V drivers in staging area yet. I still have a mixed feeling about their stability. Lots of things will com into Linux 3.0.x
For those using RHEL5-based distributions: Yes it works.
- MS announced support CentOS
56 - meaning that if you are using CentOS you can soon hope for a 'supported by MS' badge.
- I have seen proper stability using Scientific Linux 5.5, 5.6rolling as well as the CERN variant SLC56
- Recommendation: Use DKMS (it's in EPEL) and create a rpm package containing bits for your kernel that is yet installed to save time during deployment if you have multiple machines.
For all the others (Debian mainly as I use it): I have been tracking Microsoft's effort to get those hv bits in a sane state, they have hired a former Novell employee (KYS) who has done considerable cleanup on the 20k+ LoC shrinking it by a couple of thousands already. Yet, there are over 350 patches in the pipeline that will hopefully make it into Linux 3.0.x, but the staging maintainer gregk has mentioned that storvsc and netvsc needed a bunch more of cleanup.
I have an experimental branch of the 'stable' branch (2.6.39.x yet) where I cherry-picked all of these changes that are in staging-next - I just did some git log parsed and grep'ed, spiced with some sed and only 2 manual fixups where automatic cherry-picking failed. The result can be found on gitorious (at your own risk). I'll try to track the changes from stable and if possible from HV and report on my results on Squeeze. At least the storage driver showed less prone to random lockups. Netvsc still had its problems in the 2.6.38 series - because of that I kicked in the legacy NIC on all non-RHEL VMs to be safe but I will re-try soon.
Closing thoughts: It seems also with the recent rumours from MS that they think about supporting even Ubuntu - and possibly Debian, that they are serious on supporting Linux on their virtualization infrastructure, better for me as consumer on their platform. :-/