Tom Young's article on data centre CO2 levels presents a hugely generalised view of the environmental impact of data centres (Data centres hike C02 levels). In many cases using the right kind of data centre can play a part in reducing emissions.

A well-designed medium-to-large data centre actually reduces CO2 emissions compared with running the same servers in a smaller data centre in an office environment because the infrastructure to support the servers can be made much more efficient in a larger, purpose-built facility.

One measure of efficiency is the ratio of total power used by the data centre divided by the power used by IT equipment. This energy efficiency ratio (EER) highlights how much power is used by air conditioning systems and losses in electrical systems.

It can vary from 1.5 to more than three, meaning the total power consumption of the data centre (and therefore CO2 emitted) is between 1.5 and three times that used by the IT equipment.

Well-designed data centres tend to run in the range of 1.5 to two, depending on the design specification and levels of redundancy in critical infrastructure.

Just by relocating IT equipment from a data centre with an EER of three to one with an EER of 1.5 effectively halves CO2 emissions.

Most third-party data centres use a billing mechanism that has a variable rate depending on power consumption. Some even provide real-time statistics of power consumption at a per-rack level.

Customers of these data centres see an easily identifiable cost for running their IT infrastructure rather than having it hidden in their own office costs.

Moreover, they can easily identify a cost saving if they switch to more efficient hardware or implement virtualisation of their server infrastructure.

As an industry we need to be focused on lowering CO2 emissions based on the useful work carried out by IT equipment. Rationalisation of hardware, more efficient hardware and virtualisation will all play a part in these reductions, as will more efficient data centres.

We must be wary of demonising data centres as a source of CO2 emissions, and instead look at the opportunities available to us by locating equipment in modern, purpose-built, efficient facilities. It is not how much power a data centre uses, but how much it saves.

Marcus Hopwood, IFL