It is best for virtualization infrastructures to be on a central storage platform. I don't plan on talking much about that at this juncture, other than to say I am running vmware servers off of NFS quite successfully.
IT shops can get many bangs for the buck running vmware infrastructure with virtual center - take weird old servers, with only internal redundancy (if that) and gain:
-- capacity planning for virtualizing new servers
-- automated help virtualizing those new servers with minimal downtime
-- as much storage redundancy as the shop can afford and manage in central storage
-- options to use central storage backup capabilities to integrate with the IT shop backup strategy - have vmware cause a central storage snapshot with vm disk use quiesced, with no interruption in service - thus no longer needing a backup client license on each (virtual) server.
-- HA - clustering and failover - and this for services that did not have it before - makes an IT manager's service uptime much better
-- Easy server upgrades - just fail server instances off the physical server you want to replace, and replace!
So who does not care about virtualization? The big web ops shops don't care. They need CPU, RAM, and networking. These new cheaper more powerful servers using less power are still awesome, but not as part of a virtualization platform. They might have tens or hundreds of servers fulfilling one purpose, not part of an old server. I'm talking about the likes of production web operations of companies like Yahoo!, Google, Amazon, Ebay, and the like. They bind many servers together (for example, behind a load balancer) to act as one.
However, big web operations like these, more and more, are creating virtualization-like capabilities in the opposite direction - making large banks of servers be able to flip-flop repurpose as needed for other purposes. This is the same problem, kind of. If virtual servers can be very efficient, but multiple servers could bond together to act as one server in some ways, then