Energy saver

4 Jan 2009

For years the industry has been discussing the ultimate green data centre, but secretly wondering what it means to be ‘really’ green. Now we need to test these claims objectively.

In a few short years, data centres will emit more greenhouse gases than airlines. The cost implications of this are not yet clear, but if they are half as heavy for our sector as they have been for the airline industry, we will need to fasten our seatbelts.

At the same time, Moore’s Law has driven the cost of powering IT higher than the cost of the IT equipment itself. Energy prices are rising too. According to the Uptime Institute, the cost of power and infrastructure for IT as a percentage of budget is moving from 1–3pc a few years ago into double figures. All of the factors driving an energy-efficiency programme – environmental, political, corporate, commercial – are converging into a single commonsense imperative: save money by saving energy, starting now.

Some people would still rather talk about green data centres than build and operate them, which can lead to confusion. So how do you recognise a green data centre? It boils down to measurement. The key calculation is power usage efficiency (PUE), or the science of maximising the amount of useful power delivered to the IT equipment for each unit passing through the data centre transformer. Total data centre energy usage divided by IT equipment energy usage gives you PUE.

So, for instance, the dream green data centre would have a PUE of 1, which means that every watt of power at the transformer is delivered directly to the IT equipment. Unfortunately, this is not physically possible as some infrastructure services, such as cooling etc, always have to be provided.

At the other end of the spectrum, there are data centres with PUEs of anything from 2 up to 7 or 8. A PUE of 2 or more is becoming more and more unacceptable these days, because it means that more energy is being spent on powering infrastructure for IT than on powering the equipment itself. These are typically in-house data centres based on legacy equipment, but they do include some data centres managed by dedicated providers. Today’s green data centres lie between these extremes.

Green standards

How this compares with the rest of the sector is not yet easy to say with authority, but we want to make sure that everyone will know as soon as possible. For the sake of full disclosure, Interxion has been collaborating with the Uptime Institute EMEA and the Green Grid to agree a set of universal usable ratings for energy and power efficiency. Progress in this area is also being shared with the Joint Research Committee of the European Commission, which has been tasked with developing the industry’s first pan-European voluntary code of practice.

The standards will simply reward existing best practice. Data centre infrastructure power overhead – that is, transformer load over IT hardware load – can be converted to a percentage value to create DCI-PE – data centre infrastructure power efficiency. This measure was developed by Interxion and circulated to both the Uptime Institute and the Green Grid. In addition, I expect that PUE will be the key calculation behind a broader energy rating with more relevance to customers – the data centre infrastructure efficiency rating (DCI-E).

Green data centres have other characteristics in both design and operations. In order to minimise the power overhead, a green data centre should never be over-specified for the task it performs. This is why the modular data centre build-out approach, pioneered by Lex Coors, director of engineering at Interxion, has now become the norm across the industry. Some energy-efficient components are now standard. Free-cooling on chillers, for instance, is now a non-negotiable element in a green data centre.

In addition, smart procurement drives efficiency gains over time. Efficiency-focused design engineering requirements, which approach the energy flow of the data centre as an integrated system, are the key. For instance, a strict policy should be in place for selecting UPS providers, floor systems or high co-efficient of performance chillers, which work efficiently in combination.

For the dedicated carrier- and vendor-neutral data centre provider, there is one more characteristic essential to making a data centre green: green customers. If your data centre PUE is less than 2, then the greater part of the power spent in the data centre is used to power customer IT equipment. Everyone recognises that there are huge opportunities for gaining efficiencies at minimal cost in the short term. Our role is to support and advise.

As well as keeping its own house in order, the truly green data centre should be a focal point for enabling these customer efficiencies by sharing best practice on installation, providing energy usage measurement and analysis advice and offering a range of tools and services. Working together with our customers, we can make the energy efficiency of the equipment at the heart of the data centre as green as the infrastructure of the data centre itself.

By Tanya Duncan, managing director, Interxion Ireland