New metric can help gauge benefits of data center consolidation

Global task force, including DOE and EPA, agrees on a way to measure energy efficiency

A global task force that includes the U.S. Energy Department and the Environmental Protection Agency has recommended that a metric developed by the Green Grid become the globally-accepted method for determining energy efficiency in data center facilities.

Organizations in Europe and Japan have joined the two federal agencies and the Green Grid to establish the power usage effectiveness (PUE) metric as a common method for data center operators to measure and improve their infrastructure energy efficiency.

The efficiency of data centers has become an important topic globally as data center managers deal with power, cooling and space limitations. Escalating demand for data center operations and rising energy costs have prompted organizations to assess and improve their performance with efficiency metrics. However, these metrics are often not applied consistently at a global level.

“We saw there was a lot of confusion in the marketplace as to how to measure energy performance in data centers,” said Paul Scheihing, acting partnership development and deployment supervisor with DOE’s Industrial Technologies Program.


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As a result, DOE, EPA and Green Grid officials started working with other U.S. organizations last year to choose a common metric. At the same time, organizations in Europe and Japan indicated they wanted to work with U.S. organizations on the same issue. Over the past year, the groups have been trying to reach a consensus.

The result is an ongoing collaborative effort, called “Harmonizing Global Metrics for Data Center Energy Efficiency,” which is focused on improving data center energy efficiency and greenhouse gas emission efficiencies.

Participating organizations include the Energy’s Save Energy Now and Federal Energy Management programs; EPA’s Energy Star program; European Commission Joint Research Centers Code of Conduct; Japan’s Ministry of Economy, Trade and Industry; Japan’s Green IT Promotion Council; and The Green Grid, a consortium of academia, IT industry and government.

The Green Grid PUE metric is a measurement of the total energy of a data center divided by the IT energy consumption. The Green Grid recently announced additional metrics to complement PUE, including carbon usage effectiveness (CUE) and water usage effectiveness (WUE), designed to help data center operators assess the sustainability of their facilities.

Acceptance of the metric should help the federal government’s energy efficiency and data center consolidation initiatives, Scheihing said. Reducing the number of federal data centers by 40 percent by the year 2015 is a key goal of the Obama Administration’s Federal Data Center Consolidation Initiative.

The DOE plans to incorporate PUE rules into the Data Center Profiler Software Tool Suite (DC Pro) to support federal consolidation initiatives, said Scheihing, who is advising DOE officials on Energy’s consolidation efforts.

DC Pro is an online software tool provided by DOE to help industries and organizations worldwide identify how energy is being purchased and consumed by their data centers and also identify potential energy and cost savings.

The DC Pro tool will continue to be upgraded to meet the requirements of participants in the Data Center Energy Practitioner Program. DOE and industry have developed a certificate process to qualify energy practitioners to evaluate the energy status and efficiency opportunities in data centers. Currently, 150 people have been certified, Scheihing said. They have documented knowledge and skills, including proficiency in the use of DC Pro.

Some observers have noted that PUE, though useful and endorsed by energy efficiency mavens, has limitations as a tool for achieving greater levels of efficiency. Getting to the next level of data center efficiency requires a metric that connects energy consumption to the work output of the IT systems, they say.

The metric harmonization team is involved in a multi-phase mission, said Mark Monroe, Green Grid executive director. A metric that measures data center productivity hasn’t been decided upon, yet, he noted.

The Green Grid is promoting a family of data center resource optimization metrics called Data Center Productivity metrics. The first metric within that family is the data center energy productivity metric. Alternative metrics are being proposed, including IT consulting firm Gartner’s Power to Performance Effectiveness rating, which allows managers to compare their IT equipment’s average performance against optimal maximum targets that they’ve set.

Meanwhile, the Green Grid unveiled three sustainability metrics at its Green Grid Technical Forum and Member’s Meeting earlier this week:

  • DCcE, or data center computer efficiency, a metric that enables data center operators to determine the efficiency of their compute resources, which allows them to identify areas of inefficiency. DCcE is an important piece of the ongoing work by the Green Grid to determine data center productivity.
  • WUE, or water usage effectiveness, a metric that assesses the water used on-site in operating a data center, including water used for humidification and water evaporated on-site for energy production or cooling of the data center and its support systems.
  • ERE, or energy reuse effectiveness, a metric for measuring the benefit of reusing energy from a data center, and provides operators with greater visibility into the energy efficiency opportunities in identifying and recovering energy from their facilities.

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