8 radical ways to reduce data center power costs

One or more of these wild-eyed approaches could save you a lot of money -- and not cost you much

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Radical energy savings method 2: Power down servers that aren't in use
Virtualization has revealed the energy saving advantages of spinning down unused processors, disks, and memory. So why not power off entire servers? Is the increased "business agility" of keeping servers ever ready worth the cost of the excess power they consume? If you can find instances where servers can be powered down, you can achieve the lowest power usage of all -- zero -- at least for those servers. But you'll have to counter the objections of naysayers first.

For one, it's commonly believed that power cycling lowers the servers' life expectancy, due to stress placed on non-field-swappable components such as motherboard capacitors. That turns out to be a myth: In reality, servers are constructed from the same components used in devices that routinely go through frequent power cyclings, such as automobiles and medical equipment. No evidence points to any decreased MTBF (mean time between failure) as a result of the kinds of power cycling servers would endure.

A second objection is that servers take too long to power up. However, you can often accelerate server startup by turning off unnecessary boot-time diagnostic checks, booting from already-operational snapshot images, and exploiting warm-start features available in some hardware.

A third complaint: Users won't wait if we have to power up a server to accommodate increased load, no matter how fast the things boot. However, most application architectures don't say no to new users so much as simply process requests more slowly, so users aren't aware that they're waiting for servers to spin up. Where applications do hit hard headcount limits, users have shown they're willing to hang in there as long as they're kept informed by a simple "we're starting up more servers to speed your request" message.

Radical energy savings method 3: Use "free" outside-air cooling.
Higher data center temperatures help you more readily exploit the second power-saving technique, so-called free-air cooling that uses lower outside air temperatures as a cool-air source, bypassing expensive chillers, as Microsoft does in Ireland. If you're trying to maintain 80 degrees Fahrenheit and the outside air hits 70, you can get all the cooling you need by blowing that air into your data center.

The effort required to implement this is a bit more laborious than in method 1's expedient cranking up of the thermostat: You must reroute ducts to bring in outside air and install rudimentary safety measures -- such as air filters, moisture traps, fire dampers, and temperature sensors -- to ensure the great outdoors don't damage sensitive electronic gear.

In a controlled experiment, Intel realized a 74 percent reduction in power consumption using free-air cooling. Two trailers packed with servers, one cooled using traditional chillers and the other using a combination of chillers and outside air with large-particle filtering, were run for 10 months. The free-air trailer was able to use air cooling exclusively 91 percent of the time. Intel also discovered a significant layer of dust inside the free-air-cooled server, reinforcing the need for effective fine-particle filtration. You'll likely have to change filters frequently, so factor in the cost of cleanable, reusable filters.

Despite significant dust and wide changes in humidity, Intel found no increase in failure rate for the free-air cooled trailer. Extrapolated to a data center consuming 10 megawatts, this translates to nearly $3 million in annual cooling cost savings, along with 76 million fewer gallons of water, which is itself an expensive commodity in some regions.

Radical energy savings method 4: Use data center heat to warm office spaces
You can double your energy savings by using data center BTUs to heat office spaces, which is the same thing as saying you'll use relatively cool office air to chill down the data center. In cold climes, you could conceivably get all the heat you need to keep people warm and manage any additional cooling requirements with pure outside air.

Unlike free-air cooling, you may never need your existing heating system again; by definition, when it's warm out you won't require a people-space furnace. And forget worries of chemical contamination from fumes emanating from server room electronics. Modern Restriction of Hazardous Substances (RoHS)-compliant servers have eliminated environmentally unfriendly contaminants -- such as cadmium, lead, mercury, and polybromides -- from their construction.

As with free-air cooling, the only tech you need to pull this off is good old HVAC know-how: fans, ducts, and thermostats. You'll likely find that your data center puts out more than enough therms to replace traditional heating systems. IBM's data center in Uitikon, Switzerland, was able to heat the town pool for free, saving energy equal to that for heating 80 homes. TelecityGroup Paris even uses server waste heat to warm year-around greenhouses for climate change research.

Reconfiguring your furnace system may entail more than a weekend project, but the costs are likely low enough that you can reap savings in a year or less.

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