green IT
A TOOL FOR ITS TIME
The success of PUE showed that the data centre industry was hungry for a tool to measure efficiency – now The Green Grid ’ s new Performance Indicator ( PI ) has the potential to further transform the industry and our increasingly connected society , as Mark Seymour of Future Facilities explains .
The introduction of the Power Usage Efficiency ( PUE ) ratio in 2006 , by The Green Grid , transformed the way data centres were perceived within and outside the industry . While it took some time to gain currency , in recent years an increasing focus on energy usage has led to almost every new data centre promoting their PUE score as a badge of efficiency and a demonstration of their green credentials . It started the trend but has received its fair share of criticism and it didn ’ t tell the whole story .
Designing and running the data centres of the future Data centres need to be not only energy efficient , but also effective in cooling during normal operating conditions and designed for failure or maintenance scenarios . Data centres come in many different shapes and sizes too . A data centre for an investment bank for example might forgo efficiency to deliver faster transactions . On the other hand , those dealing with large volumes of users on the web every day would focus on efficiency because of the magnitude of consumption , tolerating small delays in favour of potentially massive energy savings .
These are examples at the extremes of the spectrum of data centres , where measuring PUE would give vastly different results and , in the case of the investment bank example , might even be irrelevant in what they are trying to achieve . Then there are all the data centre applications in between , where PUE is important to varying degrees . It is no longer sufficient simply to measure energy efficiency . Other metrics are required that consider both the role and the effectiveness of a data centre .
Building on the foundations of PUE While PUE showed there was a strong appetite within the sector for an independent measurement tool , The Green Grid ’ s new Performance Indicator ( PI ) takes the foundation established by PUE and builds upon it to deliver a tool that is indispensable for data centres around the globe .
The new tool focuses on three elements . The first , PUE , focuses on energy efficiency , looking at how effectively the facility is operating in relation to defined energy efficiency ratings . PUE remains a key component in the new tool , allowing facilities to measure their green credentials and demonstrate improvements in performance .
The second , IT Thermal Conformance , examines how much of the data centre ’ s IT equipment is operating at recommended inlet air temperatures during normal operation . The ratio helps understand how much , if any , IT equipment is operating with increased risk outside recommended ranges .
Finally , IT Thermal Resilience measures the equipment at risk of overheating in the case of a cooling failure or during planned maintenance . It is this final metric that allows facility managers to understand how their data centre will behave when redundant cooling systems are not operating ( ie . N out of N + X units are operating ). This can be done either through measurement – when cooling systems are off or under maintenance – or more effectively and safely through the use of simulation software .
The reason for considering all three metrics simultaneously is that a positive change for one may result in a negative change for another . So it is imperative that the business sets a target for each in order to be able to prioritise decisions that maximise the value of their investment for the business .
The critical value of PI There are four levels of PI , ranging from the basic measured assessment of the current state of the data
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