141
pumps), Access systems, Video surveillance, Lighting, Control station,
Monitoring systems, KVM Systems, Fire extinguishing systems
Unfortunately, just like with the MVEG consumption referred to earlier on,
people tend to cheat. For example the exhaust heat from the datacentre,
which can be recycled in the most favourable case (building heating, hot
water treatment), is deducted from the bill.
The PUE factor indicates how carefully the datacentre provider uses the
supplied energy. But it doesn't tell you anything about the efficiency of the
systems that are supplied. Another important point is that the PUE factor is
an annual figure, thus eliminating seasonal fluctuations. For example, in
some locations free cooling is used in the winter, therefore eliminating
energy‐intensive cooling systems from the invoice, and vastly improving the
PUE. The next question we must ask ourselves is how the provider operates
its systems. Surveys have revealed that server systems which are not
working at full capacity most of the time (this is obvious when nobody is in
the office, which is the case most nights), and are operated in a very
inefficient way.
Thanks to a high degree of virtualisation, many logical servers can share a
physical server; this helps to achieve good load levels on the server systems
and therefore high efficiency. Therefore, virtualisation, no matter what
technology is used, is a must‐have in the datacentre.
But it is precisely this virtualisation that makes the PUE factor worse. How
can this be? The problem here is that it is actually the overhead, consisting
of the management systems/cooling/safety systems, that is measured. Now,
if the degree of the virtualisation increases, and servers that are not used
are shut down, this increases the PUE factor, since the overhead is now
greater relative to the number of servers. You still need the same number of
fluorescent lights, video cameras, access systems etc., to manage what are
now less servers.
These and other considerations have led to the introduction of the CUE
standard.
The CUE factor
The CUE standard was created as another factor in the xUE Suite by The
Green Grid Organisation. The idea was to introduce a method that also takes
into account the issue of sustainability. To allow this to happen, the existing
PUE factor was extended to include CO
2
emissions.
