Impact of rack-level compaction on the data center cooling ensemble

The growing energy consumption of computer data centers has recently received increased economic and environmental scrutiny. A significant portion of typical data center energy consumption can be apportioned to the cooling infrastructure. This paper shows the impact of heat load within the data center on the efficiency of the data center cooling ensemble, as measured in terms of a ´grand´ Coefficient of Performance of the ensemble (COP_G). The paper begins by developing an expedient, semi-empirical model of the cooling infrastructure in an actual data center in Bangalore, India. These predictions are compared to experimental measurements at various levels of the ensemble, with good agreement between predicted and measured values. Having validated the model, the impact of replacing low-density racks with high-density blades into the data center is explored. For the test case considered in this paper, it is found that consolidation leads to greater efficiency of the infrastructure components, causing COP_G to increase by about 15%. The paper concludes by quantifying the impact of this consolidation on the total cost-of-ownership (TCO). For the test case, the consolidation results in improved utilization of the infrastructure, thus effectively reducing the burdened TCO (per Watt of computation) by up to 30%.