Which two containment configurations are most common in modern data centres?

The two most common and fundamental approaches to airflow containment in data centers are Hot Aisle Containment (HAC) and Cold Aisle Containment (CAC). In CAC, the cold aisle is enclosed with doors and a roof, creating a contained supply of cold air for the server inlets. In HAC, the hot aisle is enclosed, capturing the hot exhaust air and ducting it directly back to the cooling units. Both methods serve the primary purpose of separating supply and return air streams to improve cooling efficiency.

B. Vertical and horizontal are terms describing the physical components (e.g., vertical panels, horizontal ceilings) used to build a containment system, not the configuration itself.

C. "Left and right containment" is not a standard industry term for data center airflow management configurations.

D. "Open containment" is a contradiction in terms, as the purpose of containment is to enclose an area. "Closed containment" is redundant.

1. ASHRAE. (2018). Design Considerations for Datacom Equipment Centers (13th Ed.). Chapter 6, "Cooling," pp. 6-18 to 6-20. This section explicitly details and diagrams "Cold-Aisle Containment" and "Hot-Aisle Containment" as the primary strategies.

2. U.S. Department of Energy. (2012). "Data Center Best Practices: Hot-Aisle/Cold-Aisle Containment." Fact Sheet, DOE/EE-0721. The entire document focuses on explaining the implementation and benefits of these two specific configurations.

3. Schneider Electric White Paper 135. (2011). "Hot Aisle vs. Cold Aisle Containment for Data Centers." The title and content of this widely-cited paper establish these two configurations as the principal options for data center containment.