While power and cooling have always been core data center issues, with the price of providing these essentials now rivaling the cost of the computing gear itself, it's time to take a new look.

In a Network World audiocast on the subject, Bob McFarlane, a principle of Shen Milsom & Wilke in charge of data center design, says studies show that in the normal 18 months to five year lifespan of systems today, the total energy investment to power and cool those devices will equal or exceed the original investment in that equipment.

(If you're wondering what equipment only lasts 18 months, McFarlane says that's how fast some of his high-end financial services clients upgrade systems.)

The increasing cost of energy is partially to blame, McFarlane says, but it is also a byproduct of the corporate quest for speed and reliability. "That means more processors, more redundancy, more density and higher clock speeds, all of which generate more heat, which requires more cooling."

The high costs, coupled with the fact that high-density systems like blades make for concentrated hot spots, are forcing experts to rethink the way they design data centers. McFarlane says it is better to design around zones rather than treating the whole room uniformly. "We're getting away from watts per square footage and starting to talk about watts per cabinet or watts per cabinet footprint."

And distributed systems that put the cooling near the source of heat make a lot of sense, he says. The closer you get the heat source to the cooling the more efficient it will be. "It makes it easier to control the airflow."

The most common data center design mistake McFarlane sees is old hands simply resorting to the tried and true, what he calls designing out of a file drawer. Too much has changed and there have been too many advances for that approach to provide the efficiencies possible today.

Two other common mistakes he sees: the failure to design far enough into the future and a willingness to take into account the sometimes-hard-to-believe forecasts floated by various industry associations. "You always have to design for considerable more capability than people believe."

And get used to the idea of bringing water back into the data center, just like the old mainframe days, McFarlane says. The need is coming back.