One of the most significant cost elements with is the centralized storage required for maintaining virtual machines. Hypervisor vendors argue that to get disaster recovery and high availability the additional expense is really a bargain. And in many instances that might be true. But in many cases cost is paramount, complexity is to be avoided and three or four nines of availability may be far down the list of priorities.

Availability and uptime are always important, but don't forget that will improve uptime and availability regardless of whether centralized storage is used. So the real question is whether a fairly significant improvement in availability is good enough if it comes with low-cost, reduced complexity and fewer moving parts. Many IT shops will probably nod in the affirmative.

OUTLOOK:

VIRTUALIZATION WARS:

Centralized storage is typically implemented with storage area networks that provide redundancy, network accessibility and management features that go beyond conventional, local storage. For example, tools allow you to add disks to your array(s) without discontinuing service. And hypervisors leverage these capabilities to deliver improved uptime and high availability through support of features like live virtual machine migration (also referred to as in VMware parlance).