I just read an interesting article regarding the potential cost pitfalls associated with VM sprawl. Jett Thompson, an enterprise computing architect from Boeing, has developed a cost model regarding the benefits of virtualization and the related pitfalls of VM sprawl. It seems that virtualization is easy to justify, so long as you don't give the users everything that they want. Here is the money quote from the article:

However, all of those savings [from virtualization] can be eliminated if sprawl isn't controlled. With virtual servers easy to spin up, users may ask for large numbers of new virtual machines and it's up to IT to hold the line, Thompson says.

"If you don't have demand management and good governance in place you're actually going to cost your company money," he says. "Virtual server sprawl can wipe out any savings.

Gartner analyst Thomas Bittman also says virtual server sprawl can be tough to control and is harder to measure than physical server sprawl. "Fundamentally, we believe virtualization sprawl can be a much bigger problem than physical sprawl," Bittman said.

I believe that the unintended consequences of "IT hold[ing] the line" will be rogue cloud deployments. Rogue cloud deployments describe the phenomenon of business unit developers taking matters into their own hands when IT "holds the line" on making computing resources available. Once the business units understand that resources can be made available on-demand, either internally or via services such as Amazon EC2, they are simply not going to take "no" for an answer. Deploying applications as virtual machines, or virtual appliances in the case of an ISV application, removes all of the friction from the deployment process. This same friction was formerly the tonic that IT sprinkled about in order to "hold the line" on availability (and the subsequent management costs) of computing resources. The instant gratification culture that we are cultivating with SaaS and cloud will not be held in check if IT "holds the line" by saying "no" to requests for capacity/capability.

I have a recommendation for Jett and the folks at Boeing and elsewhere who are fearing the unintended consequences of frictionless system capacity brought about by virtualization. Push the control point for deployment policy upstream via automated build, release, and management processes for applications released as virtual machines; manage the scale problem by going vertical with a JeOS architecture; and build a seamless bridge managed by IT to cloud offerings like Amazon EC2. Charge the users with the costs for deployment and management, but give them the technology to do it the right way. Check out our cloud computing adoption model and the webinar that accompanies it. Rogue cloud deployments can be avoided, even in the face of VM sprawl control measures, when you say "yes" to your users while holding them accountable for building manageable system images.