New Metrics from The Green Grid

Arthur Cole
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Keep Your Cool in the Data Center

The more tightly you pack heat-generating equipment, the more energy you consume trying to cool the air in and around it. An efficient cooling system is a top priority.

As promised, The Green Grid introduced a new pair of metrics designed to supplement its widely used, but often criticized, Power Usage Effectiveness (PUE) system-a move designed to help enterprises gauge their energy efficiency more effectively.

The question, though, is whether additional calculations like these will form a clearer picture of IT energy use or muddy the waters even further.

The metrics are called Carbon Usage Effectiveness (CUE) and Water Usage Effectiveness (WUE) and are intended to quantify the amounts of those two elements that a given data center produces or processes under normal operating conditions. Details of the CUE calculations-essentially the center's PUE multiplied by its carbon output-are available now at the organization's website, while WUE specs will be out in February.

Of the two, WUE looks to be the more difficult measure to quantify, according to Peter Judge at eWeek Europe. That's because water is not actually consumed during the cooling process but merely cycled through cooling elements and sometimes returned to the environment. That means the measure will have to assess the quality of the water being used, rather than the quantity, to have any meaningful impact. And both metrics will still be incomplete because neither takes into account the water and carbon involved in the manufacturing and disposal of enterprise gear.

These new measurements also come at a time when many enterprise executives are still trying to figure out PUE. According to Keysource, less than one-third of data center managers know their own PUE rating, although that is an improvement over the last year's awareness of 25 percent. The funny thing is, average PUE across the industry is dropping, from 1.93 at this time last year to 1.89 today.

That's probably because most enterprises do not need fancy metrics or complicated calculations to determine whether energy use is declining-all they need to do is look at their energy bills. As CDW points out in its third annual Energy Efficient IT report, nearly 75 percent of survey respondents are actively working to reduce consumption, although only 15 percent have factored PUE into their efforts.

None of this is to say that PUE, CUE, WUE and any other measurement/analysis technique is a waste of time. On the contrary, a broad set of metrics is the only way to gain a complete picture of overall data center health and efficiency.

These are complex environments after all, and any attempt to whittle all of the factors at play into a single number will fall woefully short of the green IT mark.

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