Cooling capacity and cost metrics for energy efficient workload placement in datacenters

Energy usage in the data centers has been increasing drastically in the recent years attracting many studies in power and thermal management in data centers. However, research has been focused mainly at power management of IT equipment and efficiently delivering cooling resources for a given IT load distribution. To further increase the energy efficiency of data centers, an integrated approach to preferentially placing IT load at locations of highest cooling efficiency is necessary. Such cooling aware workload placement can bring substantial savings when coupled with the migration of workload away from less cooling-efficient locations and the powering down of machines that are not in active use. Along with cooling-aware migration, it is critical to quantify the available cooling capacity and the cooling cost to support additional heat load at different locations in a datacenter to affect placement of new workload and, from a longer term point of view, for IT planning purposes. This paper presents novel thermal metrics which can be used to estimate available cooling capacities for different thermal zones in an operational datacenter. The thermal metrics also show the local distribution of the available cooling capacity at different racks within a thermal zone. The paper will also present another new metric called localized cooling cost which is utilized to rank locations with respect to costs incurred for cooling additional workload. We utilize CFD simulations for a case study showing application of the metrics.