My data center airflow is fine ... almost

My data center airflow is fine ... almost

Are your data center hot spots under control?

Managing a data center is an all-or-nothing type of endeavor. You can't "sort of" succeed or be "mostly" successful. This is because there is significant dependency among variables in these dynamic facilities. If one detail is slightly off, others risk being affected in a chain reaction. 

Consider, for instance, what happens if only one specific part of your facility, be it a single cabinet, or a certain row, becomes a hot spot. If equipment in this section overheats, causing an outage, the immediate damage is the risk of downtime for your organization – or your client. For the sake of argument, let's say you have a failover in place in a different section of the data center. This may cushion potential losses; however, the very act of switching on the equivalent load in a different sector of the facility will impact environmental conditions in that area. If your airflow cannot immediately adjust to these new conditions, even your redundancies are at risk of failing. 

When it comes to data center cooling, if there is a "but," "except for" or "almost" following the statement, "my data center airflow is fine," then your data center airflow is not fine. 

What causes hot spots?

"The primary cause is not enough cold air being delivered to the cold aisle," wrote TechTarget contributor Robert Sullivan. Several factors may precipitate this occurrence, namely, the following:

  • Bypass airflow: This is when conditioned air doesn't reach the equipment it's supposed to be cooling. This typically occurs when air is not being properly drawn into servers, but rather, is sneaking through crevices and mixing with air in the hot aisle.
  • Poor exhaust containment: If hot air that has already fanned servers is not properly contained, it won't necessarily reach the return plenum. Instead, it risks mixing back into the cold aisle, which in turn raises the temperature of the air that's supposed to be conditioning the equipment. 
  • Proximity to the CRAC unit: In some cases, specific racks, cabinets or entire rows are located too far away from computer-room air-conditioning (CRAC) units. As a result, there is in an insufficient concentration of treated air actually reaching the equipment to cool it off. 

All of these are inherently problematic since they can result in damaged equipment. However, the mitigation approach that many operators take – dialing up the cooling capacity – won't actually solve the problem. This is because it's not a cooling deficiency, it's a fault in airflow management. As a result, the problem persists, and data center managers waste energy on AC.

Spending on higher cooling capacity will start to add up over time.Spending on higher cooling capacity will start to add up over time.

Eliminating hot spots: Here's how to do it right

"You need to address the reasons they exist in the first place."

If you want to get rid of hotspots in your data center, you need to address the reasons they exist in the first place, which is that not enough cool air is getting to the equipment. This entails ensuring that cool air is consistently being drawn into cabinets, rather than passing around or through them – and equally as important, that it's actually reaching the equipment in the first place. To this end, an airflow management and containment system that employs pressure sensors to control fan speeds can help solve this problem by increasing rpm as needed. Not only will this help limit bypass airflow, but it will also make sure that cabinets placed farther from the cool-air source won't be denied treated air. 

As for containment, it's vital that exhaust on the hot aisle is reaching the return plenum, and has no chance of mixing back into the room. This will help stabilize the data center temperature in your hot spots without cranking up cooling capacity. In the long run, this will cut back on expenses in the data center, according to TechTarget contributor Clive Longbottom. 

If your end game is lower operational expenses and the elimination of hot spots, you need a solution that's as good at making sure cool air reaches equipment as it is diverting exhaust into return plenums. Only then, can you say that your data center airflow is fine.