Since the inception of the computers in the early 60’s, airflow within the space has been an important consideration from the design perspective. But this aspect has often been misunderstood. Considering the low density of computing that was done
back in those years, this design factor did not make its presence felt. However, today with enormous amount of computing done and high performance servers doing double the amount of work compared to their predecessors, airflow management in a data center becomes important.
The most important principle behind an effective airflow management system is-
- Minimizing the mixing of inlet and outlet exhaust gases: The purpose of this can be achieved by deploying the following-
- Cool air from the cooling units (CRAC) are allowed to reach only the server intakes.
- Hot air from the server goes only to the CRAC exhausts.
- The second important principle to be borne in mind is that the CRAC temperatures from the returns are to be raised to high temperatures while compensating with lower temperatures for the inlet air.
This would in turn allow the servers and the heat rejection systems to operate efficiently. This also makes way for reduced operating costs with greater server accountability.
After the analysis of the principle, it is important to understand the maintenance of these systems on a regular basis. How does the operator know if the cooling systems are operating efficiently? For this purpose we may look into the raised floor data center, whose basics are synonymous with any data center.
Data center layout needs to be cross checked before going ahead with the installation of the cooling systems. The most efficient layout will have the Hot/Cold aisle configurations in racks with an ability to extract hot air from the racks and return to the CRAC exhaust. This means that the CRAC has to be placed perpendicular to the rows.
Rows ideally should be 8 or more racks long with a full 2 tile wide cold aisle. Racks fronts should be even with the tile edges so that any tile in the cold aisle can be removed or replaced to allow adjustment of cold air volume. One of the biggest issues with blanking panels is making sure they are replaced when work is done in racks. Racks should be 3 full tiles away from the CRACs to minimize low flow from tiles that are too close to CRACs. Where possible, place less server load in racks at the ends of the aisles and higher loads in racks towards the middle of the row. Additionally load racks from bottom to top, keeping the highest server loads lower in the racks.
Containment is becoming a popular strategy for airflow management in data centers. Its specialty is that it uses a physical barrier to reduce, or in some cases completely eliminate mixing which allows higher CRAC supply and return temperatures.
Every data center is different and has varied airflow challenges and opportunities but the subset of problems in each has known and proven solutions. Airflow management, properly applied, will reap benefits in energy efficiency, IT capacity and server reliability.
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