Unlike benchmarking standards like SPECpower standard for servers, the Green Grid's PUE (Power Usage Effectiveness) and newly renamed DCiE (Data Center Infrastructure Efficiency), provides broad data center guidance for power management.
Increasingly we are seeing new measurements for Information Technology power measurement and management - from intricate individual server benchmarking (like SPECpower) to broad data center measurement. The Green Grid's two standards - PUE and DCiE fall into the latter category.
PUE is effectively a measurement of [Total Facility Power / IT Equipment Power] and DCiE is measured as [(IT Equipment Power / Total Facility Power) / 100%. Within both measurements, Total Facility Power is the power measured at the utility meter (specifically for the data center facilities) and includes everything from air conditioning to lighting to generators. And IT Equipment Power includes all data centre IT infrastructure, from servers and network equipment to other components such as KVMs.
These measurements provide a baseline to allow businesses to compare other data centres and improve their own data efficiencies.
So what is a good rating? Green Grid recommend a PUE rating of 1 is equivalent to 100% efficient. However reality, in the form of a small study by Lawrence Berkeley National Labs found that 22 data centres had a PUE ranging from 1.3 - 3.0.
There are two key issues with the measurements, which The Green Grid freely admit:
- there is no agreement on what an efficient data actually is, and
- apart from the one study mentioned previously, there isn't really any comprehensive data on current PUE ranges, the comparative points currently are essentially non-existent.
All current data centre metrics (whether its the EPA's Data Center metrics or The Green Grid's) are in early stages so there will be a tussle over which one becomes the industry standard. However something is better than nothing so at the very least, the more data centres that measure their energy use, the better metrics like these become over the next few years.
The Green Grid 2007, The Green Grid Data Center Power Efficiency Metrics: PUE and DCIE
Lawrence Berkeley National Laboratory 2006, Best Practices for Data Centres: Lessons Learned from Benchmarking 22 Data Centers