Today's data center managers are struggling to juggle the business demands of a more competitive marketplace with budget limitations imposed by a soft economy. They seek ways to reduce opex (operating expenses), and one of the fastest growing -- and often biggest -- data center operation expenses is power, consumed largely by servers and coolers.
Alas, some of the most effective energy-saving techniques require considerable upfront investment, with paybacks measured in years. But some oft-overlooked techniques cost next to nothing -- they're bypassed because they seem impractical or too radical. The eight power savings approaches here have all been tried and tested in actual data center environments, with demonstrated effectiveness. Some you can put to work immediately with little investment; others may require capital expenditures but offer faster payback than traditional IT capex (capital expenses) ROI.
[ Unlearn the untrue and outdated data center practices in Logan G. Harbough's "10 power-saving myths debunked." | Use server virtualization to get highly reliable failover at a fraction of the usual cost. Find out how in InfoWorld's High Availability Virtualization Deep Dive PDF special report. ]
The holy grail of data center energy efficiency metrics is the Power Usage Effectiveness (PUI) rating, in which lower numbers are better and 1.0 is an ideal objective. PUI compares total data center electrical consumption to the amount converted into useful computing tasks. A not-uncommon value of 2.0 means two watts coming into the data center falls to one watt by the time it reaches a server -- the loss is power turned into heat, which in turn requires power to get rid of via traditional data center cooling systems.
As with all simple metrics, you must take PUI for what it is: a measure of electrical efficiency. It doesn't consider other energy sources, such as ambient environmental, geothermal, or hydrogen fuel cells, many of which can be exploited to lower total power costs. The techniques that follow may or may not lower your measurable PUI, but you can evaluate their effectiveness more simply by checking your monthly utility bill. That's where it'll really matter anyhow.
You won't find solar, wind, or hydrogen power in the bag of tricks presented here. These alternative energy sources require considerable investment in advanced technologies, which delays cost savings too much for the current financial crisis. By contrast, none of the following eight techniques requires any technology more complex than fans, ducts, and tubing.
The eight methods are:
- Crank up the heat
- Power down servers that aren't in use
- Use "free" outside-air cooling
- Use data center heat to warm office spaces
- Use SSDs for highly active read-only data sets
- Use direct current in the data center
- Bury heat in the earth
- Move heat to the sea via pipes
Radical energy savings method 1: Crank up the heat
The simplest path to power savings is one you can implement this afternoon: Turn up the data center thermostat. Conventional wisdom calls for data center temperatures of 68 degrees Fahrenheit or below, the logic being that these temperatures extend equipment life and give you more time to react in the event of a cooling system failure.
Experience does show that server component failures, particularly for hard disks, do increase with higher operating temperatures. But in recent years, IT economics crossed an important threshold: Server operating costs now generally exceed acquisition costs. This may make hardware preservation a lower priority than cutting operating costs.
At last year's GreenNet conference, Google energy czar Bill Weihl cited Google's experience with raising data center temperatures, stating that 80 degrees Fahrenheit can be safely used as a new setpoint, provided a simple prerequisite is met in your data center: separating hot- and cold-air flows as much as possible, using curtains or solid barriers if needed.
Although 80 degrees Fahrenheit is a "safe" temperature upgrade, Microsoft's experience shows you could go higher. Its Dublin, Ireland, data center operates in "chiller-less" mode, using free outside-air cooling, with server inlet temperatures as high as 95 degrees Fahrenheit. But note there is a point of diminishing returns as you raise the temperature, owing to the higher server fan velocities needed that themselves increase power consumption.