From Legacy to the Modern-day Data Center Cooling Systems

Modern-day Data Centers provide massive computational capabilities while having a smaller footprint. This poses a significant challenge for keeping the Data Center cool, since more transistors in computer chips, means more heat dissipation, which requires greater cooling. Thereby, it has come to a point where traditional cooling systems are no longer adequate for modern Data Center cooling.

Legacy Cooling: Most Data Centers still use legacy cooling systems. They use raised floors to deliver cold air to Data Center servers, and this comes from Computer Room Air Conditioner (CRAC) units. These Data Centers use perforated tiles to allow cold air to leave from the plenum to enter the main area near the servers. Once this air passes through the server units, heated air is then returned to the CRAC unit for cooling. CRAC units have humidifiers to produce steam for running fans for cooling. Hence, they also ensure the required humidity conditions.

However, as room dimensions increased in modern Data Centers, legacy cooling systems become inadequate. These Data Centers need additional cooling systems besides the CRAC unit. Here is a list of techniques and methods used for modern Data Center cooling.

Server Cooling: Heat generated by the servers are absorbed and drawn away using a combination of fans, heat sinks, pipes within ITE (Information Technology Equipment) units.1 Sometimes, a server immersion cooling system may also be used for enhanced heat transfer.

Space Cooling: The overall heat generated within a Data Center is also transferred to air and then into a liquid form using the CRAC unit.

Heat Rejection: Heat rejection is an integral part of the overall cooling process. The heat taken from the server is displaced using CRAC units, CRAH (Computer Room Air Handler) units, split systems, airside economization, direct evaporative cooling and indirect evaporative cooling systems. An economizing cooling system turns off the refrigerant cycle drawing air from outside into the Data Center so that the inside air can get mixed with the outside air to create a balance. Evaporated water is used by these systems to supplement this process by absorbing energy into chilled water and then lowering the bulb temperature to match the temperature of the air.

Containments: Hot and cold aisle containment use air handlers to contain cool or hot air and let the remaining air out. A hot containment would contain hot exhaust air and let cooler air out while cold containment would do vice versa.3 Many new Data Centers use hot aisle containment which is considered as a more flexible cooling solution as it can meet the demands of increased density of systems.

Closed-Couple cooling: Closed-Couple Cooling or CCC includes above-rack, in-rack or rear-door heat exchanger systems. It involves bringing the cooling system closer to the server racks itself for enhanced heat-exchange.2 This technology is very effective as well as flexible with long-term provisions but requires significant investments.


Companies can choose a cooling system based on the cooling needs, infrastructure density, uptime needs, space factors, and cost factors. The choice of the right cooling system becomes critical when the Data Center needs to have high uptime and avoid any downtime due to energy issues.

Sify offers state of the art Data Centers to ensure the highest levels of availability, security, and connectivity for your IT infra. Our Data Centers are strategically located in different seismic zones across India, with highly redundant power and cooling systems that meet and even exceed the industry’s highest standards.

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