"We would ultimately like to get to the point that we can generate reports for chargebacks," says Christopher Ware, vice president of technology services at a brokerage firm in New York.

The problem, he says, is that virtual machines are pooled resources, so IT must figure out not only how to measure usage but also how to attribute costs for virtual machines and the shared, underlying hardware. Adding to the complexity, both the number of virtual machines and utilization levels for a given application can vary over time.

"A mature virtualization management tool should be able to not only allocate resources and manage them but also generate the necessary accounting to facilitate chargeback and generate capacity reports and things of that nature," Ware says.

Eric Kuzmack, IT architect at Gannett Co., also would like to see more detailed reporting of usage allocations and the ability to tie those back to billing. "While in our environment we don't do chargebacks, a lot of environments do, and the virtual machines still cost the company money," he says. Management tool vendors are noncommittal.

"You can't do it today," acknowledges David Wagner, director of solution marketing at BMC Software Inc. "Our [product] can give you resource utilization by application across physical and virtual environments, but we don't put a dollar value on that."