Another balancing act is figuring out the costs of the licenses for your guest VMs versus the cost of the hypervisor or physical server pieces that you need to run them.
VMware in particular has one of the most complex licensing and pricing details, although they have taken steps to simplify it over the past couple of years. One of the advantages of going with Microsoft's HyperV running on the Enterprise version of Windows Server 2008 is that you can have unlimited free licenses for your guest Windows VMs, which can add up to a significant savings. Citrix's licensing is a bit easier to understand and price out than VMware's.
One of the ways around the issues of security and control that make some businesses wary of cloud computing is to build a private cloud -- one that remains within the corporate firewall and is wholly controlled internally. Private clouds also increase the agility of IT an organization's IT infrastructure and make it easier to roll out new technology projects. Download this eBook to get the facts behind the private cloud and learn how your organization can get started.