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INDUSTRY INSIGHT

3 tips for optimizing data center cooling

Cooling has always been a critical component of the data center environment. Computer systems generate waste in the form of heat, and like all waste, that heat must be removed for the systems to function properly.

In a traditional data enter environment, computer room air conditioner (CRAC) or computer room air handler (CRAH) units are used to cool the entire facility. The chilled air may be pumped into the room through ducts or distributed via a raised floor system. However, this approach does not take into account the location of the equipment or the distribution of power among the various IT workloads.

CRAC/CRAH cooling systems are therefore highly inefficient and can lead to “hotspots” that can harm sensitive equipment. To prevent unplanned outages and performance problems due to unmanaged heat, data center operators often overprovision cooling capacity. This wastes massive amounts of energy without solving the problem.

As data center heat loads continue to increase, government agencies need a new strategy for keeping the environment cool while keeping a lid on energy costs. In-row and adiabatic cooling, coupled with aisle containment, can dramatically reduce cooling costs and the risk of hotspots in data centers of all sizes. Data center infrastructure management (DCIM) systems can give operators the data they need to further optimize cooling efficiency.

Here are three strategies agencies can use to better cool their data centers:

1. Eliminate hotspots

Data center hotspots are not caused by inadequate cooling capacity but rather by problems with airflow -- the chilled air is not reaching the IT equipment. Agencies can resolve airflow issues by bringing cooling systems closer to the heat load and ensuring that chilled air does not mix with hot exhaust air.

As the name suggests, in-row cooling units are placed directly within a row of racks and cabinets. The cooling units may be suspended from the ceiling, placed on top of a cabinet or mounted on the floor. Best-in-class in-row cooling systems are housed in enclosures with similar dimensions to a data center cabinet.

In-row cooling systems create a shorter airflow path than CRAC/CRAH units, so the chilled air reaches the IT equipment more quickly. Virtually all of the cooling capacity is used to dissipate heat.

Combining in-row cooling with aisle containment further increases efficiency. Aisle containment systems are designed to prevent the mixing of chilled intake air with hot exhaust air. Traditional data centers often use hot aisle containment, in which racks and cabinets are arranged with the server exhausts facing each other. The hot exhaust air is isolated and sent directly to the CRAC unit. In-row cooling is often used in conjunction with cold aisle containment -- the cold aisle is enclosed to create a closed-loop arrangement that focuses chilled air on the equipment.

2. Use the power of evaporation

Most data center cooling units are direct expansion (DX) air conditioning systems, which use a refrigerant to directly cool the air coming into the unit. As data center power densities continue to increase, however, many data centers are using water to cool equipment. This is particularly true for agencies that are adopting GPU-accelerated systems for data analytics and other compute-intensive workloads.

Water has about four times the thermal capacity of air, making it an efficient medium for cooling. In the typical data center system, water is chilled to about 59 degrees Fahrenheit using a DX unit, then pumped to a CRAH. The CRAH draws warm air through the chilled water coils and into the IT environment. Heat is dissipated by pumping the water back through the chiller.

Adiabatic systems, which are based upon the cooling properties of evaporation, can be even more efficient, use less water and require less maintenance than chilled water systems. Ambient air is passed through a wet filter that cools it. The air then enters the cooling system at a lower temperature, which allows for more efficient operation.

3. Measure and manage

The optimal cooling system for any given data center depends upon its size and geographic location, the type of equipment and the power density. In addition, cooling requirements change continually as equipment is added or replaced and racks and cabinets are moved around.

Agencies can ensure proper cooling for their data centers through the use of DCIM systems. These tools perform a wide range of functions, including the real-time monitoring of energy consumption of IT equipment and infrastructure components. DCIM software pulls the data into dashboards and other visualization tools to help operators better understand power consumption. Some DCIM systems have cooling management modules that make it easier to correlate energy and cooling data. External cooling management systems can also be integrated with DCIMs.

The need to manage data center heat loads is as old as computing technology. What’s changed in recent years are the tools operators have at their disposal to effectively cool equipment while reining in energy costs. Government agencies that are looking to optimize their data centers would be wise to investigate in-row and adiabatic cooling, aisle containment and DCIM systems.

About the Author

Marcus Doran is vice president and general manager with Rahi Systems, Europe.

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