Watch this space
He says another common mistake that data center teams face when dealing with blade servers is space allocation.
"You have this perception that because the blade servers are smaller and vertically mounted, you'll be able to put more in a rack. That's not always true," he says.
Stein says that traditional server chassis hold one horizontal-mounted server per rack unit. With blades, the chassis tend to be seven or nine rack units and deliver 14 independent blades. However, this higher-server density also brings related increases in power and cooling requirements.
Andi Mann, analyst at Enterprise Management Associates, agrees that blade servers can be deceiving. "You can't rack up two or three next to each other; sometimes you can't even fill up a whole rack," he says.
He encourages data center teams to plot out their equipment needs. "You need tools to help you understand your hot spots and where you need to run power. Remember, you're colocating a lot more power drain into a single circuit, and you need to ensure you aren't overloading the system."
Planning, other tools for the job
He suggests pre-empting problems by implementing dedicated power and space planning programs such as Visual Network Design Inc.'s Rackwise and Aperture Technologies Inc.'s Vista. He adds that applications such as Hewlett-Packard Co.'s Insight Power Manager track ongoing consumption.
John Rowell, chief technology officer at OpSource, says not planning ahead of time leads to cost issues down the road. "For larger server deployments, you really have to become a power expert, otherwise you'll get burned on costs," he says.
OpSource, a software-as-a-service provider, expanded its data centers during 2005 and 2006, increasing the pool of blade servers to more than 850 and sending the power demand through the roof. Coupled with the rising price of power during that time, he says costs increased by more than two and a half times what they started with.
Rowell says that because they had agreements in place with customers before that time, they were unable to pass the costs along to customers. "We've had to soak up a lot of those fees," he says.
Although OpSource is a service provider, in-house IT staffers might keep this situation in mind especially if they engage in chargeback or other budgeting practices that require user departments to pay for the IT resources they consume.
Rowell says there are two primary drivers for a move to blades: the number of servers required to support today's applications, and the increase in CPU and memory needed to support those applications. "Faster processsors and larger memory chips that come in these servers need more power to run. This combination has created a multiplier effect on the power requirements of data center deployments," he says.
To ensure that they are on target when purchasing equipment, Rowell says his team uses software tools to do a CPU/memory to watts analysis. "It typically requires three times the server CPU/memory capabilities to run an application today than was required in 2001," he explains.
Cerner's Smith says there are other considerations with blades, too, such as rack size. "Depending on how many chassis you put in a rack, they are getting taller. If you don't plan for it, the doors into the rooms might not be tall enough. We've had to replace some doors," he says. The height also poses a problem for cabling. "We do our cable management overhead to make sure we have enough room," he says.
There are some Band-Aid measures that companies can put in place to ease blade servers' power and cooling burden on the data center. "You can leave blank floor tiles around the racks to get cold air in; you can get a back door that sends heat out of the room; and you can bring water into the data center to cool it. There are lots of work-arounds," Smith says.
But he warns, "All that can add up. So the pluses of using blade servers can get outweighed by the cost of dealing with the high power and cooling needs."