Virtualization champions enthuse about how easily virtual machines can be deployed–often in minutes, compared to the days or weeks for their physical counterparts. (Not to mention the additional time required for capital expense approvals.)
The flip side of this instant gratification is the risk of VM sprawl–that unfortunate little phenomenon where oodles of virtual machines are added to the data center without coordination, management or policy.
While virtualization itself reduces the number of physical servers in a corporate environment, it often increases the number of virtual machines, since they are so easy to deploy. Such instant gratification has its downside. VM sprawl can destroy the ROI of your virtualization deployment by crowding out legitimate VMs and reducing user satisfaction with performance and response time of the host server. If you have planned for an 8:1 consolidation ratio and found yourself congratulating yourself with an 18:1 achievement instead, be careful before you celebrate. The physical host server may not have been budgeted and configured with the additional horsepower, and now your phone is ringing off the hook because everyone’s applications are performing worse than before. And, by the way, where did those extra machines come from? Who configured them? Why didn’t you know?