Beating the PUE Acronym to Death

Julius Neudorfer

By now everyone involved in the data center has heard about the Power Usage Effectiveness (PUE) metric that was originated and defined by The Green Grid.  In an interesting marketing ploy, Trendpoint has come up with the concept of 'Micro PUE.'

They claim that 'Micro PUE' represents the performance of individual CRAC systems by measuring the input energy vs. the actual cooling delivered in BTUs.  Not coincidentally, they manufacture a monitoring unit (Envirocube) that they say will measure the actual cooling delivered by a data center CRAC. 

They go even further: If one accepts their premise of the existence of 'Micro PUE,' then they now can introduce by inference the term 'Macro PUE,' which they postulate is really a better term than just PUE, since they hypothesize that PUE really reflects the data center's cooling efficiency ('This paper has shown that PUE is essentially a measurement of the cooling efficiency of a data center in relation to its IT load'). Moreover, that by measuring the 'Micro PUE' (presumably by purchasing their Envirocubes), you can have more granular information to help improve your 'Macro PUE.'

Even within their own white paper, it states:

 'As a brief description, Micro PUE is the actual amount of energy used to process and cool 1 kWh of IT load through a given cooling unit.'

By definition, PUE is a ratio, not 'the actual amount of energy used,' so even if I were to accept their premise of a 'Micro PUE,' I am confused by their description.

I agree that being able to monitor each CRAC unit's operating efficiency can be a very useful tool to optimize and balance the cooling system. However, inventing the term 'Micro PUE' seems to me to be an extreme case of riding the PUE bandwagon a little too far. Guess what, cooling system performance (and sub-components) already have several well-defined efficiency metrics: Coefficient of Performance 'COP or CP,' and Energy Efficiency Ratio 'EER.' These existing efficiency metrics express the performance ratio of the amount of energy required to remove a given amount of heat.

By the way, in the very first sentence of their nine-page white paper, they incorrectly refer to 'PUE' as Power Usage Efficiency, rather than the correct term, Power Usage Effectiveness. While all manufacturers offer white papers that directly or indirectly help them promote their products, Trendpoint should get the award for creative writing for this one.

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Oct 20, 2011 10:10 AM kurs valut kurs valut  says:
Thank you for this valuable post. It changed my approximation Reply

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