Rack cooling is similar to the row method except that the CRAC units are dedicated to and mounted within a specific rack. In this system, airflow paths are even shorter and more exactly defined than either the room or row systems, so much so that they're immune to any installation variation or room constraints.
All of the rated capacity of the CRAC can be utilised, enabling the highest power density (up to 50 kW per rack) to be achieved. The rack-oriented architecture also has the same benefits as the row system in terms of increased efficiency, and highly targeted cooling and redundancy. The main drawback of this approach is that it requires a large number of air conditioning devices and associated piping when compared to the other approaches, particularly at lower power density.
Hybrid is the way forward
All data centres are designed for a common purpose of providing a secure and reliable structure for housing IT equipment. While these data centres are united in a common design goal at a very high level, they are very diverse in nearly every other way. Each data centre has unique demands that are driven by individual business needs. Even into the operational phase, the uniqueness of the data centre continues to change with the rate of expansion, density, and layout, to name a few. With a design life of 10-15 years for the data centre and IT managers refreshing their equipment every 2-4 years, it is likely that the data centre will change significantly over the years.
In the face of constant evolution, choosing a single cooling solution that will meet the data centre needs today and in the future is a difficult task. For this reason, most data centres will require a hybrid approach i.e. a mix of the aforementioned methods to address their unique requirements.
NUS opts for hybrid
For its new data centre, the National University of Singapore (NUS) has opted for the hybrid approach, one of the few organisations in the region to do so.
Deployment of high density loads in IT environments can create areas of unpredictable cooling performance. The legacy approach to data centre cooling is inadequate for the medium and high density zones that the university has deployed in its new data centre facility, possibly giving rise to issues such as creation of hot spots, system downtime due to overheating and increased operational costs due to inefficient cooling.
A hybrid rack and row approach is used in this case - a modular rack containment system is deployed to support the medium and high-density zones in the NUS data centre facility. Designed to contain clusters of high-density equipment up to 8kW and 15kW respectively, this standardised system acts as a self-contained mini data centre within a data centre with dedicated row-based cooling to prevent hot server exhaust air from escaping into the room effecting sensitive IT equipments.
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