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Mar 31st - Hot Aisle Vs. Cold Aisle Containment in The Data Center

When planning and constructing a data center, one of the most immediate threats to the wellbeing of your infrastructure is heat. Surely, we’ve all been seared by our computers and gaming systems after leaving them running too hard for too long. Your computer is just single unit though, so it's easy to imagine how when you start to stack up multiple rackmount servers in a single room, it can get pretty hot fairly quickly. So how to data center designers manage to keep it cool when servers are literally running on-end 24/7? They implement temperature containment systems that allow the heat that is produced by servers to be redirected and managed.

2 of the most common types of heat containment systems are hot aisle and cold aisle containment. In both instances, servers are organized into rows with every other aisle being isolated inside a room within the data center. This separation makes controlling the temperatures of the air directly surrounding the servers much more manageable. The primary differences are essentially where the hot / cold air is being routed.

With Hot aisle containment, servers are aligned in rows facing away from each other with a row in-between that is large enough for maintenance. With this setup, all of the heat coming from the backs of the servers ends up in this middle row. From there it is sucked up into vents lining the ceiling of this “hot aisle” into precision air conditioning unit, which usually utilize water to control temperatures. These units typically cycle the hot air from all of the hot aisles from the ceiling into the space beneath a raised platform upon which all of the servers in the datacenter reside. Cold air is pumped up into the uncontained space surrounding the front sides of all of the servers.

Cold aisle containment systems are essentially the same but with the roles of the contained space and uncontained space somewhat reversed. Here, the contained space holds the cold air, which cools the servers while the remaining, uncontained space holds all of the heat that the servers produce.

Research has shown that containing the hot aisle rather than the cold can save as much as 43% on energy costs over cold aisle containment. Similar research has shown that hot aisle containment allows the inlet chilled water supply temperature to be higher on average, which makes way for more hours of free air cooling (lower air temperatures cool the water that is cycled). Additionally, the Cooling setpoints can be set much higher while maintaining the pleasant standard indoor design temperature of 75.2 degrees Fahrenheit for workers in the area.

The costs of setting up cold and hot aisle containment systems are essentially identical. So while it could be argued that the right engineering could yield even better results with a cold aisle containment system, it still makes sense for most data center planners to opt for the hot aisle solution. Plus your maintenance workers will thank you for it in the long run.