Energy-Efficiency Metrics Are The First Step - InformationWeek

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Energy-Efficiency Metrics Are The First Step

Accurate measurements can help IT save power and money, but plan carefully to avoid false starts.

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electric meter IT leaders face ever-increasing pressure to reduce power consumption in the data center and beyond. Whether it's the corporate desire to cut costs in every area or customers' growing environmental awareness, that pressure amounts to a lot more than friendly reminders to turn off the lights.

But once all the off switches have been hit and unused devices unplugged, how do you know what your next steps should be? A good place to start is to figure out just how much juice your gear consumes, relative to non-IT devices. Armed with this information, you can take steps to reduce the overall energy footprint of your data center, then the rest of your facility.

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Still, building an accurate energy profile is a challenge for many organizations. You can't improve what you can't measure, yet the meter on the outside of the building doesn't tell you how power gets allocated once it's inside. Specialized measuring devices like the Kill A Watt can't be used on all your gear.

Green Measures
Enter the Green Grid, a nonprofit consortium of IT professionals and vendors, which has developed two energy metrics that can help IT staffs calculate and trend efficiency: Power Usage Effectiveness (PUE) and Data Center Infrastructure Efficiency (DCiE). Although these metrics are used primarily in data centers, the concept can certainly be adopted in other areas. For example, you could figure out how much of an office building's total power relates to heating/cooling or office equipment using either metric.

The PUE metric expresses efficiency as a fraction in which total facility power is the numerator and IT equipment power is the denominator. IT equipment power includes the load associated with all IT-related equipment, from computers, storage, and network gear to keyboard, video, and mouse switches; monitors; and workstations. Total facility power includes IT equipment power plus power delivery components such as switch gear, uninterruptible power supplies, generators, batteries, and cooling system components.

The Green Grid's DCiE expresses efficiency as the inverse of PUE (rendered as 1/PUE). Both metrics measure the same data in the same fashion, and a value of 1 is the ideal (albeit impossible to achieve) result in both cases. The major difference is the way that each expresses the measurement. DCiE tells you how much load your IT equipment is using, as in 75% or 0.75 is dedicated to IT load. PUE can tell how much additional load is required to support your IT equipment, or how much of your electricity use is not dedicated to IT devices.

Impact Assessment: Energy Metrics
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