Top risks of improper exhaust containment in the data center

Top risks of improper exhaust containment in the data center

While rare, fires have started as a result of improper data center cooling.

The expulsion of hot air from the data center is just as important, if not more important, than the infusion of cool air. In fact, you can't really have one without the other. Servers will continue generating heat as long as they're operational, which should be every second of every day. A failure to contain and expel this heat as cool air is introduced would be sort of like trying to cool a room while the heating vent is still on. 

In fact, a failure to properly contain server exhaust precipitates several big risks in the data center, including the following: 

1. Wasted resources

Cooling accounts for about 40 percent of all data center energy consumption. That's substantial when you consider that total power usage of U.S. data centers was approximately 70 billion kilowatt-hours in 2014. Given the amount of money this represents, data centers should be doing everything in their power to cut back on consuming more energy than necessary, including proper exhaust containment. 

For smaller, less dense facilities, a passive exhaust system may be the most energy-efficient way to expel hot air that's passed through equipment into the hot aisle. Server fans will draw in air from the cool aisle and push it out into the hot aisle. As long as cables don't block airflow and the return plenum pressure is negative, this "passive" system is ideal.

However, as server density in racks and cabinets increases, so does the likelihood that airflow will become restricted. As a result, CRAC units will have to work harder to maintain optimal temperature conditions, ultimately leading to wasted energy. The proper solution for these situations is active containment of exhaust through the use of chimneys that direct hot air into the return plenum. 

2. Mixing of hot and cold air

In an ideal airflow and containment system, hot and cold air shouldn't be facing off. In an ideal airflow and containment system, hot and cold air shouldn't be facing off.

Exhaust in the hot aisle should never mix with cool air in the cold aisle, but that's exactly what happens if containment isn't properly managed. This results in two big problems. First, it could cause the reflexive increase of cooling capacity, which as mentioned above, increases resource consumption. As long as exhaust drifts into the cold aisle, temperatures may continue to steadily rise and so will your energy bill.

The second problem is hotspots. These occur when the area immediately surrounding server air intake fans is too warm or too dry. This can happen is if exhaust circulates back into the cool aisle instead of reaching the return plenum. 

Hotspots can be particularly difficult to address since they tend to be isolated to specific racks or cabinets. It's therefore important to ensure that poor containment isn't what's causing them. If certain racks or cabinets are simply too far from the cool air source, pressure-sensitive fans built into active chimneys will automatically increase speeds to help server intake fans draw in the required amount of cool air. This type of containment prevents warm air from cycling back into the cold aisle, while also ensuring that enough cool air is reaching servers in the first place. 

3. Overheating equipment

"The outcome could be downtime, or something worse."

If hotspots are not adequately addressed, servers may operate at higher-than-recommended temperatures. As a result, more sensitive electrical components may have a shortened lifespan. 

The more immediate concern, however, is overheating. If one or more servers overheats to the extent that it is no longer functional, the outcome could be downtime, or something worse. While rare, there have been instances in which fires have started as a result of improperly cooled equipment becoming too hot. 

That said, if you properly contain exhaust and support healthy airflow through the use of smart fans embedded in chimneys, you significantly curb the risk of downtime, or a data center disaster, while lowering your operational expenses. 

To read more about effective exhaust containment, click here