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Green IT
What is our understanding of Green IT?
In the past, this has been understood to be the efficient use of energy; this
understanding also manifests itself in the PUE factor, which we will
introduce in the next chapter.
But today we have a different understanding; the new equation is:
Green IT = Energy efficiency + renewable energy.
What use is the most efficient datacentre if the energy comes from a lignite
fired power plant, or a much less efficient datacentre that uses a a mix of
hydroelectric, photovoltaic and wind power?
Let's take a closer look at the topic of energy efficiency.
The PUE factor
How can we imagine the PUE factor?
Just as there is a MVEG consumption for every vehicle, there are also
metrics for system efficiency in IT.
A number of initiatives in the last few years have ensured more efficiency of
individual appliances in recent years. For example, the Energy Star
Initiative
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which kitemarks energy saving devices. This makes it easier for
the consumer to decide whether an appliance is an energy saver or not; a
quick look at the Energy Star database is all it takes, and you can choose the
biggest energy saver in the class. This isn't quite as easy for datacentres;
there are many components that need to be considered for these
computations. But to provide a means of simple comparison, the Green
Grid‐Organisation, mentioned previously has created a global standard.
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The PUE factor or "Power Utilisation Efficiency" is the measure of the
efficiency of a datacentre. It is computed from the sum of the electrical
power supplied that reaches the power supply of the system hosted in the
datacentre. It is therefore always greater than 1 but should be as close to 1
as possible; if it was less than 1, the IT systems would generate electricity,
which is fairly unlikely. The metric covers the energy consumption of the:
UPS system, Air‐conditioning system (compressors, refrigeration units,
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