Kate's Comment

Thoughts on British ICT, energy & environment, cloud computing and security from Memset's MD

Greening the data centre: Why

I’ve written before about going green being important for business, but now I’d to focus on one area: the data centre. There has been a lot of interest recently in the topic of “green” data centres. however, many organisations still seem to feel that being more energy efficient in is just pandering to the general worries about global warming and of little importance to the fundamentals of the business (until they start running out of power at any rate!). In this, the first of three articles on reducing power usage in the data centre (“Why”, “How” and “Measuring IT”), I’ll make the case for why it is not just environmentally responsible to look at your IT infrastructure’s efficiency, but that it makes solid financial sense too.

The recent flurry of interest in getting the power consumption down in data centres in the UK has in large part been driven by a swathe of city firms suddenly realising that not only are they running out of power in their current central-London data suites, but they can’t get any more space and capacity either – power is already being reserved for the 2012 Olympics, for example. Also, there are a number of city data centres being run at dangerous capacities, and I’ll be watching with interest when the first of those super high density suites goes into thermal runaway after a brief power outage; the chillers are not run off the UPS, and therefore are shut down for a few mins while the backup generators start. At high power density in confined spaces that is potentially long enough to result in a non-reversible catastrophic failure process (similar to one we have seen in action). I suspect we may see a major bank with melted blade servers in the near future…

But I’m rambling; I’m not interested in those power-and-space constrained city firms (they should just move their non-trading- / non-latency-sensitive back-office applications out of town), my point here is that all CIOs should be taking note of their IT infrastructure’s energy usage. Why? Well on the one hand it is good for PR – in a recent survey that my company, Memset undertook 48% of the new customers we gained since going Carbon Neutral in August ’06 said that energy efficiency was “important” when choosing a supplier. Interestingly, only 39% said offsetting / carbon neutrality was important, which suggests to me that buyers are realising that treating the cause is better than treating the symptoms.

On top of the good PR, as an industry we need to be prepared to combat negative press on the issue. Recent calculations based on server sales in the UK estimate that 1.9% of the UK’s grid power goes to powering data centres, which is a massive amount. Some papers used a similar figure from Gartner (that the UK industry worldwide contributes 2% of total greenhouse emissions) to compare us with the airline industry (who also contribute 2% apparently, which is further worsened by the greenhouse effect of contrails), but that at least is easily dismissed; the IT sector contributes something like 10% to UK’s GDP, so we are putting our 2% power usage to very good use at least! Regardless, I would not be surprised to see data centres becoming targets of environmental protests in years to come if we are not careful.

Even if we put all that wholesome planet saving stuff aside for a moment though there is a still a solid reason to be taking energy efficiency in the data centre seriously: a few simple steps can much more than halve the electricity bill.

First lets consider the changes in server power usage. I did an article in May ’06 (getting value for wattage) highlighting the improvements in server energy usage, and since then things have improved even further with the advent of Intel’s multi core chips. Take a standard £1,000 ($2,000) Dell 1U “workhorse” server. Eighteen months ago that got you a dual Xeon machine that used about 200W when working at moderate load. Today, we are buying dual core machines that, thanks to Dell & Intel’s good work on efficiency, are more powerful yet use only 100Watts under moderate load (in other words the same as a bright light bulb).

Next lets factor in the changes in data centre infrastructure technologies and design in the last few years. At our new Reading site 70%+ of the power entering the building actually gets to power the servers. This gives a Power Usage Effectiveness (PUE) figure of roughly 1.5, erring on the side of pessimism. PUE, by the way, is the Green Grid’s proposed metric on measuring data centre efficiency. In my third article in this series (“Measuring IT”), I will explain why it is not a useful metric in practical terms and why the one going into the EU Data Centre Code of Conduct (being developed with the British Computer Society’s Data Centre Specialist Group and Intellect UK) makes more sense. For simplicity though it serves its purpose here; in many older data centres, the PUE is as high as 3 or 4 (ie. Only 25-33% of the power entering the building actually reaches IT kit). I’ll talk about how data centres can be made more efficient in the next article (“How”), but for now lets apply those figures to our workhorse example servers’ power usage.

For meaningful comparison I’m going to look at the costs in any one month. For the hardware, three years is a realistic lifetime so £1,000 over 36 months gives an amortised cost of £28/month ($56/m).

The 18-month old dual Xeon, when housed in a fairly average two year old data centre (I’ll be generous and give them a PUE rating of 2), would double its power usage (cooling, UPS inefficiencies etc), which gives us a figure of 400Watts which, at 10p/KWh, gives us a electricity bill of £29/month ($58/m). Yes – that is more than the cost of the hardware!

Our new, low-power dual core machine, installed in our nice energy-efficient modern data centre (PUE 1.5) gives us a total energy bill (at 10p/KWh again) of £11/month ($22/m). In other words, by installing modern, basic servers (not expensive, over-complex blade centres) in a modern data centre (most of whose efficiency gains are achived without massive cost of complexity), you can save £600-700 ($1,200-1,400) over the lifetime of a £1,000 server!

A final thought; those figures don’t include an allowance for carbon taxation or offsetting, and one should also bear in mind that commercial electricity prices have doubled in recent years, and look set to continue to rise, at least until they are at a level where nuclear power is commercial viable again. In short, taking note of your IT infrastructure’s energy efficiency can have a very significant effect on your bottom line.

In the next installment I’ll talk about some of the simple, practical steps that can be taken to improve a data centre’s power efficiency, as well as some methods of reducing the number of machines you need in the first place.

No comments yet...