Disaster recovery, to many people, means not much more than a hot site, but there is much more involved. What exactly is involved depends on how much money you have to put to the problem. Fully redundant hot sites cost quite a bit in hardware, software, and licensing. At best, they should be exact duplicates of your current environment; at worst, they should be able to run your most important virtual machines. However, this is not the only aspect of DR that should be considered. Disasters come in all sizes, from the small-scale application failure to the catastrophic natural disaster. Both of these are fairly well understood. But what about the middle of the road business-continuity and disaster issues, which somewhere in between the extremes in the scope of disaster, but are specific to virtualization infrastructures: single machine failures, SAN failures, VM failures, etc.