For those of you that are hard core virtualization folks, there is an excellent couple of articles over at xen.org by George Dunlap from Citrix.
In the ESX world and Hyper-V world the virtualization is closer to the HVM type or PVHVM when the OS is enlightened. Xen has grown from a different root and started from the paravirutalization world (true PV, it is actually kind of interesting how the VMs themselves boot in this world).
This also gives a bit of background into the terminology and options that are available.
Personally, I think it good reading for anyone working with machines as it is a history of evolution in one aspect.
At this same time we have MSFT Research working on the Library OS. This is an interesting abstraction of applications into VM type containers, application containers. This is more similar to the traditional Xen PV model, where (technically) there isn’t a boot kernel in there, just the runtime components of the machine and the bootstrap comes from the xen hypervisor itself. (at least that is my impression of it).
The MSFT research project known as Drawbridge: http://research.microsoft.com/en-us/projects/drawbridge/
And a bit more: http://research.microsoft.com/apps/pubs/default.aspx?id=141071
And a Channel9 presentation for the short attention spans among us: http://channel9.msdn.com/Shows/Going+Deep/Drawbridge-An-Experimental-Library-Operating-System
Other MSFT Research OS projects: http://research.microsoft.com/en-us/groups/os/
Is this the future? the Application level virtualization that was discussed many years ago. Decoupling the application from the OS? Not really the decoupling, but the forcing of an application into a container. A container that it cannot get out of and affect other applications.
I look at this and think about traditional application compatibility issues going away, true application throttling, true isolation of a session (and its applications) within a Terminal Server. That is what really makes me think about where this is all headed. And we continue to be just at the beginning of it all.