Desktop virtualisation is something that I haven’t really honed-in on before.
There is a valid question to ask as “how important is a single desktop in terms of its availability?” The answer is probably “not very important” as some recovery time would almost certainly be acceptable.
However, the hosts today are supporting an enormous amount of desktop sessions so the real question becomes “what is the impact of a 1000 desktop sessions all failing at the same time?”
The answer to this is, of course, completely different.
My answer is to protect the environment with fault tolerant technology. It goes beyond this though. It is emerging that, in most VDI architectures, the broker server is the most important element. So, even if you don’t run the host environment on protected hardware, the least you should be doing is running the broker application on a bullet-proof platform.