Well, I have to admit that I was pleasantly surprised by Server 2012 and the improvements to HyperV. The major improvements that I have noticed since I started using it are these:
1. Live Migrations between Cluster Hosts are insanely fast. This is due to compressing the data between the two hosts. You notice a slight bump up on the processors (maybe going from 2% utilization to 12%), but it’s not enough to do anything. I’ll be the first to say that this feature is amazing – migrations take literally a few seconds – these are VMs with 6GB of dynamic memory (using about 2 gigs).
2. Virtual Machine Version 2.0. I haven’t used this much yet, however, some of the features look great and some don’t look so good. The main one is boot from SCSI disk and shared SCSI disks. That means you can create Virtual Clusters with extreme ease. The problem with Virtual Machine Version 2.0 is that it’s lacking the RemoteFX stack. This is not a problem if you’re hosting servers, but if you are doing a VDI deployment (like myself) this is a bit of a problem.
3. Deduped Cluster Shared Storage. This has been something I’ve been waiting for – dedupe in Windows is awesome. In my little VDI environment, I created each individual VM (not using a template) tailored for each user. This is good and bad – it mean each user retains their settings, however, it means when you thin provision and then use 30 gigs of space in one VM, it’s 30 gigs of space used on the volume. This is not a problem for a good SAN as a good SAN will compress that in to about half that size, but when you start having 20 or 30 VMs, it still can add up. Enter deduped cluster shared volumes. Dedupe would be awesome – since most VMs are Windows 8 or Windows 8.1, they all have about 10 – 15 gigs worth of the exact same data. Dedupe will take that data and instead of having for all 20 or 30 VMs, store it only 1 time and each time a read is looking for a certain chunk of data, it will read the chunk that was deduped.
4. GPT / UEFI boot – this isn’t a huge thing since most VMs are needing 2TB+ boot disks, but for those who are, you’re in luck.
All in all, it looks like a lot of big improvement.