End User Focus
hot-aisle/cold-aisle containment seems like a no-brainer and the
next evolutionary step for data centre cooling strategies.
density, the number of KW per square handling systems can deliver enough practical purposes the containment
meter. air keeping the inlet temperature well system made no measurable difference
below 40 Celsius. to the effectiveness of the fire
Telecommunications companies have suppressant system. As long as the
used fresh air-cooling for decades for Humidity control is designed to prevent containment system does not interfere
their network equipment in telephone condensation on cold surfaces (80%) with the gas discharge nozzles it does
exchanges. Vendors manufacture most and the build up of static (10%). The not really matter if they are located in
of their computer products to operate absence of refrigeration means that the containment system, outside the
in this environment. there are no surfaces colder than the containment system or indeed under
airflow making condensation the floor void or in the roof space.
Telecommunications companies specify impossible. As input air is warmed Where there is an element of free air
operating temperature ranges up to 50 going through the room, relative (fresh air) cooling gas discharge fire
Celsius (122 F). Telecommunications humidity decreases further reducing the suppression is not particularly effective.
companies expect power densities of likelihood of condensation. Very dry
0.5 - 1.5 KW per square meter. input air is unusual in a temperate 3) Could the pressure wave from the
climate, usually only caused by gas discharge dislodge the
At BT we constructed 106 21st Century refrigeration. containment system and cause injury
Data Centres that work on fresh air- to occupants? This is a risk with any
cooling. These are not design studies When installing curtains to separate hot gas suppression system, where ceiling
but real live sites delivering service to and cold aisles it is important to tiles, floor tiles, cabinet doors and other
customers. consider the impact fire detection, fire objects can be dislodged by the gas
suppression and personnel evacuation. pressure wave. In all cases it is
How practical is fresh air-cooling? important the system is not armed
Depending on the location of your site Lets start with the impact on fire when personnel are inside the
and the maximum year round systems of having either hot or cold protected area and that emergency cut
temperature the answer is very aisle containment. The safety of off switches are provided in convenient
practical. But in almost any location, it personnel working within the data locations.
is possible to reduce the amount of air centre is absolutely critical and there
conditioning required provided that the are a number of key issues to be Numerous data centres employ hot-
external temperature is cooler than the concerned with: aisle/cold-aisle containment, including
temperature of air exhausted from your Sun Microsystems. Storage vendor
equipment for at least part of the day. 1) Are (audible or visual) fire alarm NetApp has employed vinyl curtains
signals blocked out by the containment similar to those you see at BT to
Manufacturers specifications are system? Can you hear and / or see that contain the air in the hot aisles in its
generally for the air temperature at the an alarm is going off? This needs a live Silicon Valley data centre. These
inlet to the computer equipment not the test with db monitoring equipment to curtains alone save NetApp 1 million
temperature inside the computer ensure that all building and safety kWh of energy per year.
cabinet. Note that higher inlet regulations are being met.
temperatures tend to cause the Yahoo Inc. has also employed vinyl
temperature-controlled fans inside 2) Will the gas discharge properly curtains in one of its data centres for
most equipment to operate at a higher distribute throughout the room with the airflow containment.
speed, increasing the energy used. containment system in place? Tests at
Rochdale showed that the air circulated Beyond the fire-suppression issue, hot-
Provided that exhaust air from the hot around the room very quickly (3 times a aisle/cold-aisle containment seems like
aisle is not allowed to mix with fresh air minute) and that all gas was evenly a no-brainer and the next evolutionary
in the cold aisle and that room air distributed within 30 seconds. For all step for data centre cooling strategies.
26 | DATA CENTRE SOLUTIONS | www.datacentresols.com September 2008
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