PUE

PUE - Power usage effectiveness

A typical data center facility spends almost half of its energy consumption on the systems powering and cooling the computers inside — and not on the computers themselves. Google, Efficient Data Center Summit

Last October, Google disclosed details about its data center energy usage, saying it was averaging a Power Usage Effectiveness (PUE) rating of 1.21 across its six company-built data centers. To put that into perspective, a PUE of 1 means every watt goes to computing machines. A PUE of 1.5 means that half the power goes to non-computing functions like cooling or lights.

Six months later, Google says it’s got that number down to 1.19.  So how is the search giant doing it? For a long time, nobody knew.  Google’s infrastructure was top secret. But then in early April, Google held a summit and gave everyone a peek behind closed doors. Surprisingly, what they seem to have done was follow the KISS principle. Relatively speaking, they are keeping things simple.  They have their own proprietary servers and the data centers themselves are just about as lean as you could imagine. Google’s made several tours available on YouTube — and this one (below) of a data center built out of shipping containers is just amazing.  There are over 45,000 servers housed in 45 containers.  Talk about utility computing — this container tour sure looks like a utility plant to me!

At the summit, Google reps shared best practices, saying:

The best practices we’ve presented here are the main reason we’ve been able to achieve our PUE results and can be implemented in most data centers today.

• Measure PUE (Circuit transformers)
• Optimize power distribution (High efficiency transformer and UPS)
• Manage airflow (Close-coupled cooling — Eliminate hot/cold mixing)
• Adjust thermostat  (Raise cold aisle temp)
• Use free cooling  (Chiller bypass, water-side economizer)
• Use free cooling  (Chiller bypass, water-side economizer)

Overheard: Your PUE number is like golf

“Your PUE number is like golf — the closer to 1, the better. At least that has always been the common wisdom. The goal, says experts, is to reduce your PUE. But sometimes an IT energy efficiency project can play games with that number.” Mark Fontecchio, How a virtualization and server consolidation project could hurt your PUE