Network Communications News (NCN) August 2016 | страница 26

F E AT U R E

IT load

Data centre operators need a better understanding of how IT equipment
operates and how its reliability is impacted at high temperatures.

Congestion
Edge computing is an inevitable
consequence of vastly increased data
traffic which requires more sophisticated
traffic management. With the Internet
of Things expected to comprise 50
billion devices connected worldwide
by 2020, network latency and speed of
response will require data transactions to
be contained, as far as possible, within
regional networks, to remove some of
the congestion from global networks.
Much effort has already been
directed towards the challenge of
using energy more efficiently in
data centres. Vendors of data centre
infrastructure equipment such as
cooling, air conditioning, power
supply and containment products have
produced reference designs that allow
highly predictable installations to be
constructed. They make widespread use
of metrics such as PUE to validate how
efficiently a data centre’s power can be
delivered to the IT equipment it contains.
However, PUE is limited in terms
of managing the overall energy
consumption of a data centre, measuring
only the relative difference between
power consumed on IT equipment and
that consumed on IT and infrastructure
combined. So although it is now easier
to build data centres with confidence

that a low PUE rating will be achieved, it
doesn’t automatically mean that overall
energy consumption will be reduced.
One strategy recommended by
the American Society of Heating,
Refrigerating, and Air-Conditioning
Engineers (ASHRAE) to reduce overall
energy consumption is to arrange a data
centre so that the ambient temperature
inside can be allowed to rise. If a data
centre can operate effectively at higher
temperatures, the initial thought was
that cooling equipment such as chillers
can operate in economy mode and will
not need to be deployed as frequently,
resulting in a lower energy requirement.
However, this technique has not
been widely adopted for a variety
of reasons. Apart from a natural
conservative reluctance among
engineers to change an approach that
has been seen to work effectively, the
results of allowing temperature to rise
have been mixed.
Although allowing chillers to operate
in economiser mode for a greater part
of the year produces immediate energy
savings these are offset by the greater
burden placed on other parts of the
cooling infrastructure. Dry coolers
must operate when the chillers are in
economiser mode. Furthermore, there
is an increase in the energy expended
by fans both in the server racks
t