Capacity planning needs to provide answers to two questions: What are you going to need to buy in the coming year? And when are you going to need to buy it?
Server Virtualization - News, Features, and Slideshows
Virtualizing x86 infrastructure isn't just a one-step process -- as servers change, the whole data center must change as well. While server hypervisors such as VMware's ESX, Microsoft's Hyper-V and Xen can make IT more efficient and cost-effective, many of the virtualization advantages can be canceled out when data centers rely on technology and processes that haven't been updated for the virtualization age.