Managing Your Data Center Infrastructure

Hot Aisle vs. Cold Aisle Containment

Data center environmental control is a critical issue in terms of IT efficiency and security in your data center infrastructure. Both cold aisle and hot aisle containment are effective in separating cool supply air from hot exhaust air.  However, some vendors and industry experts have claimed that one or the other is the best approach. Here is an overview of both types of data center aisle containment.

Hot Aisle Containment

A hot aisle containment system is one that that encloses the entire hot aisle to capture he hot air exhausted by the equipment. Now that this hot air is isolated, it needs to get back to the return of the CRAC/CRAH units.  The most common way to do this is through a drop ceiling plenum area.  Cooling units with top returns can be outfitted with extensions to the drop ceiling to draw in air from the hot aisle.  This reduces strain on cooling system by removing IT produced heat.  Directly returning hot air to the cooling units can improve their operating efficiency and increase capacity.  However, implementing hot aisle containment can be very difficult if there is not a ceiling plenum or if the cooling units do not have top return.

Cold Aisle Containment

A cold aisle containment system is one in which encloses the cold aisle and enables the rest of the data center to become a hot air return. This isolates the cool supply air at the server intake where it is needed most.  By eliminating any hot air re-circulation from hot aisle, it provides precise control of temperature in the cold aisle.  CRAC/CRAH unit set points can be optimized to supply air at upper ranges of ASHRAE’s recommended temperature range.

Which Containment is Better

Both hot aisle and cold aisle containment are highly effective in reducing cooling costs.  Both prevent air mixing between hot and cold aisles which is most important.  Each have unique advantages.  Cold aisle provides more control over set point temperatures.  Hot aisle returns warmer air to cooling unit which increase cooling capacity.  However, each also have their drawbacks.  While, cold aisle containment allows for set points to be raised to nearly 80 degrees, this can create unbearable temperatures of over 90 degrees for anyone working in the rest of the data center.  Hot aisle systems are much more difficult to implement in existing data centers and can result in hot aisle temperatures of over 100 degrees.  This can be very uncomfortable for anyone service equipment at the back of the rack.

The most accurate answer to which approach is best is “It depends”.  While this may seem unsatisfactory, it does depend on room conditions, IT load and cooling infrastructure. Data Center Resources specializes in aisle containment and has implemented both hot and cold aisle solutions in data centers big and small throughout the country.  We can help you determine which containment approach is best for your unique application.