hot/cold aisle

Hot aisle/cold aisle is a layout design for server racks and other computing equipment in a data center. The goal of a hot aisle/cold aisle configuration is to conserve energy and lower cooling costs by managing air flow.

In its simplest form, hot aisle/cold aisle data center design involves lining up server racks in alternating rows with cold air intakes facing one way and hot air exhausts facing the other. The rows composed of rack fronts are called cold aisles. Typically, cold aisles face air conditioner output ducts. The rows the heated exhausts pour into are called hot aisles. Typically, hot aisles face air conditioner return ducts.

A containment system can be used to isolate hot aisles and cold aisles from each other and prevent hot and cold air from mixing. Containment systems started out as physical barriers that simply separated the hot and cold aisles with vinyl plastic sheeting or Plexiglas covers. Today, vendors offer plenums and other commercial options that combine containment with variable fan drives (VFDs) to prevent cold air and hot air from mixing.

Best practices for hot aisle/cold aisle containment include:
1. Raising the floor 1.5 feet so that air being pushed by air conditioning equipment can pass through.
2. Deploying high cubic feet per minute (CFM) rack grills that have outputs in the range of 600 CFM.
3. Locating devices with side or top exhausts in their own part of the datacenter.
4. Installing automatic doors in the data center.

This was last updated in October 2009

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