Continuous Metering and Monitoring of PUE in Data Centers

by
Wendy Torell

Executive Summary

A PUE (power usage effectiveness) metering scheme in a data center can be very simplistic consisting theoretically of only two meters, at one extreme, or it can be much more comprehensive and consist of dozens of metering points. This paper provides guidance on determining what level of metering is appropriate for a particular data center, given its capacity (kW), power and cooling architecture, business objectives, and the degree to which infrastructure systems (e.g., chillers, generators) are shared.

Conclusion

Data center owners continue to be under pressure to reduce the energy consumption of their data centers. While average PUE numbers have come down for an industry as a whole, there are still many data centers that have not taken the first step of continuous metering. Proper metering and monitoring will provide you with the ability to calculate PUE for real-time operational control, site benchmarking, and site compliance (internal or external). It’s very difficult to improve what you do not measure, in a systematic way. Metering the IT load can generally be done with existing meters, either from the UPS, PDU, or rack PDUs. Metered rack PDUs provide the most accurate representation of IT load, as it eliminates losses between the UPS and the load. Measuring the total data center load can be simple if the data center is the only function in the building; or it can involve aggregating, calculating, and estimating when the data center is in a shared facility with shared systems. When budgets allow, cooling systems should be metered, as these represent the systems with most opportunity for PUE improvement. Less visibility to individual subsystems means less ability to continuously improve and/or measure the effectiveness of changes.

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