Thursday, January 7, 2010

Resolve to Measure PUE in 2010

Measure PUE in 2010! Why measure PUE after I blog about it not being perfect, just last month?
Well, it is better than nothing. Actually it is more than that, it is the minimum insight into your data center.
Think of driving your car late at night in an unfamiliar location. You have no idea were the next open gas station will be:
How comfortable would you be without a gas gauge?
This auto analogy isn't too far off. Many corporate data centers have some monitoring system to let someone know :
  • when the temperature gets too high
  • when there is a water leak
  • generator status
  • UPS (battery) status
And then on the IT side there is often some monitoring system or other keeping track of most of the critical servers, storage, backups, firewalls, even critical applications. Often there are all kinds of graphs and analysis of these systems with trends and pretty graphs over time showing how much work has been done in the data center.
With all this often real time monitoring and trending, few corporate IT managers have no idea what their date centers PUE is for any point much less over time. Though PUE would be more closely related to MPG than a gas gauge. PUE gives you a base line. As an IT or facilities director, hopefully you are looking at reducing costs in this economy for 2010. The data used to calculate PUE can easily be used to calculate energy cost of the data center.
IT directors are used to showing costs of new projects amortized over time showing costs for:
  • computers
  • storage
  • network
  • cables
  • support
  • replacement hardware
  • helpdesk
  • even data center space
but usually not electricity. Some Directors are starting to include anticipated electric costs in the projections but most still don't consider it because the costs are not in their budget. Getting individual project electric cost projections can be much more difficult than measuring the data center as a whole. Planning a major new project for 2010, maybe some virtualization or new storage. Measure PUE before and after implementation.

Getting back to the gas gauge theme, my first cars were all older than me. They all pretty much had the same instruments in the dash: speedometer, gas gauge, odometer, and check engine light. My dad was a master mechanic from the navy and he had a term for that check engine light. He called it an "idiot light" because you were an idiot to drive with it on. If you don't measure PUE then you are relying on the "idiot light" which for many data centers comes in the form of high temperature alerts, and by then things are too late.

I have several vehicles now, from my motorcycle to a prius. Now that prius puts that gas gauge and "idiot light" to shame. There is a row of lights to tell me what is going on with the engine, check engine, change oil, change filter, tire pressure, rotate tires. Right in the middle of the car is a computer display showing instantaneous MPG, MPG for since last reset, a graph of MPG for the last 30 minutes, and a gas gauge.

This is the kind of information you want for your data center. A nice little graph showing how much energy is being used every 5 minutes. If you don't measure the PUE for you data center than it is worse than driving a 1955 Cadillac with a broken gas gauge (you do not want to guess how much gas you have in a car that gets less than 10 MPG).
Lets get started in 2010 by measuring the PUE.


  1. Richard,

    I hear what you are saying, but what's your recommendation for those of us who don't have a BMS to give us readings for the various mechanical & electrical systems. We use both AC & DC powered IT eqiupment, so I can take readings from both systems and the full power draw for the building.


  2. Brent,
    You would have to look at your particular layout to find the simplest measurement points. You could use your measurements from the full building depending on what else is in the building. If the data center is a small portion of the building then the results will be less than useful though. Measuring the power as far up stream as possible while still being mostly limited to Data center use is the most accurate. Getting above the transformer that leads to the data center UPS, or at the generator transfer switch. Try to include chillers, pumps (if chilled water), and any other possible support equipment, such as lights.
    For the computer equipment load measurement, you can most easily take this on the output side of the UPS units, but for more accuracy (and more difficulty) measure at each rack PDU, and for most accuracy (and most difficulty) measure at each computer.
    There are some non-invasive devices that can be used to measure power very accurately such as :
    I can give you links to a few others if you like, but these would be for a real time constant measurement installation. If you are looking for a one time or quarterly measurement find the points that are the simplest that include the most possible equipment or get a consultant that will bring in the equipment needed and give full evaluation reports.
    Send me a note if you want more direct assistance.

  3. Richard,

    Nice post! As a car guy - your analogy is spot on. Reminds me of when I was a kid and drove ignoring my temperature gauge - only to end up roadside with a warped head on my student beater!

    Take that concept to the data center - and a lot of folks are just driving blind. Everyone is used to server failure, running out of power, cranking the cooling - but these are things that we should not be used to but rather be trying to optimize so we don't have to deal with them! There is an element of human behavior needed here. 2010 should be about an attitude change to start questioning the things we do in the data center. Rather than taking energy-cost measures - we switch to energy -efficient approaches.

    On the topic of measurement and "how do you start this change" wireless real-time monitoring devices are a simple, low cost way to get started and fill in the measurement gaps in any enterprise environment. Look for open product solutions that allow the integration of your existing assets and any data that you might be already collecting. It's as much a "data collection" issues as it is "data integration"

    On the wireless/energy management vendor side, another company (and one that I work with) is Arch Rock Corporation. Cool people, cool products. You can check them out at All the vendor sites have great reading material - so use them as educational resources to help you get up to speed on the wonderful world of PUE.

    I hope that enterprises make PUE a mandatory metric for 2010. It's time.


  4. great post