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In a data center, there are two major components which consume 50 per cent power on the installation side: one is the uninterruptible power supply (UPS) and the other is the cooling solution. The deployment of hot aisle - cold aisle containment is basically an integration of air-conditioning and servers. Once this integration happens, the machine pumps out lesser amounts of air, as needed by the servers. This arrangement saves power, which is something of a rarity these days.
In any push air-conditioning arrangement, two components need the most amount of power: the compressor and the fan. In hot aisle - cold aisle arrangement, the air needed reduces drastically as the air is needed only for the servers and not the entire room. This drastic reduction reduces the fan speed and the compressor tones down its functioning. However, there are certain things to look out for while making these arrangements:1. Always have sufficient amount of height above the racks for making hot aisle - cold aisle containment. These systems make sense if the pushing air-conditioning equipment has intelligent controller units. Only then does the equipment give the required energy efficiency levels. Unless they are connected to hot aisle - cold aisle containment, you cannot achieve the expected energy efficiency.
2. If there is a fire, people find that there are black deposits on the glass which inhibit visibility. Hence there is a need to use material which melts.
In case, you need to increase the number of servers or increase its capacity, you can always install another rack or add more servers. If the density per rack increases, it does not make sense to replicate the number of units with today's escalating space costs. With this practice, the amount of air going or coming from the server rack can be increased very easily. Since only the area which requires more cooling is provided with that amount of cold air, you can imagine the amount of power savings.
Certain best practices that you can follow while implementing the hot aisle - cold aisle system are:1. While implementing any hot aisle - cold aisle system, you should ensure that the fire management systems are up to the mark. That means that if it is a cold aisle, fire systems like FM-200 or water containment should be inside the cold aisle. If there is any damage, then these systems can activate and cool down the servers.
2. The raised floor should be at an optimum height of 1.5 feet so that the amount of air coming from pushing air conditioning equipment can pass through.
3. Deploy high cubic feet per minute (CFM) grills, which are basically the air outlets. Normal grills only provide outputs in the range of 600 CFM. So you need to install high CFM grills which have large outlets.
4. Always make it a point to use automatic doors. In case someone forgets to close the door, it could lead to mixing of the cold and hot air. Digital sensing doors are also available for this purpose.
Nowadays, servers have become intelligent, so the fans at the back of the server can moderate the speed. Thus if they need more cooling, the fan speeds will increase. None of the servers actually work in a 100% kind of a scenario. Typically, they work at 30% load. Earlier, the air conditioning equipment would have been working at 100% levels for such a load. Today, it operates at a level wherein it justifies the amount of air needed, drastically reducing the energy consumption.
About the author: Smrutiranjan Das is the product manager for rack solutions at Emerson Network Power India Pvt Ltd. He has been with Emerson Network Power since May 2005. Initially, he was responsible for marketing, then went on to handling product strategy and later moved into product management. He has an engineering degree in IT and a PGDBA in marketing.)
(As told to Jasmine Desai)
This was first published in October 2009