Virtual server sprawl kills cost savings, experts warn

Virtual server sprawl can eliminate the cost savings so many IT shops covet when they embrace server virtualization, warns a Boeing IT professional who is leading a virtualization initiative at the company.

"We're under the gun to try to find any kind of cost savings we can," says Jett Thompson, a Boeing computing infrastructure architect based in Washington state. "Virtualization has been one of the hot ones because there’s readily identified savings there."

Boeing developed a cost model to determine the savings that can be gained through virtualization, taking into account the cost of server and SAN hardware, operating system licenses, virtualization software and management tools, power and cooling, and labor costs.

Thompson, giving a presentation at Gartner's annual data center conference on Thursday, could not reveal any numbers specific to Boeing. Instead, he detailed a hypothetical model based on the same methods he used to determine Boeing's potential cost savings.

In the model, a business with 6,000 physical servers goes from 15% to 75% virtualization, using ESX Server. The business places about 20 virtual machines on each host and is able to get rid of several thousand physical servers. The hypothetical business saves $28 million over five years by going virtual.

However, all of those savings 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.

In Thompson's hypothetical cost model, a 50% growth in server demand causes the virtualization project to be unprofitable. The extra demand increases labor costs, storage needs, and means you have to keep extra physical servers. (Compare server products.)

The benefits to end users might make this an acceptable cost, depending on your business's needs, Thompson says. But it's important to take into account all the effects virtualization has on the data center.

Virtualization should bring savings in system administration labor, hardware maintenance, and power and cooling, Thompson said. Increased costs might be incurred in SAN storage and labor for physical-to-virtual migrations. But assuming you control sprawl, virtualization is typically worth it from an ROI perspective, Thompson said.

"Virtualization from a cost perspective is easy to justify," he said.