TOTAL Isolation
In terms of cooling efficiency, an ideal configuration is total isolation – the cold side of the equipment would be completely isolated from the hot side. The only path for air would be through the equipment. This way, all the cold air produced by the cooling units (CRAC or CRAH) passes through datacom equipment before it returns to the cooling unit to release the heat. Only the exact amount of energy needed to cool the equipment is expended both in terms of BTUs and airflow CFM.

Achieving total isolation while satisfying the users need to access the equipment and manage power and data connections is challenging. Most schemes meet the goal in varying degrees and at different price points.