Cooling – making efficient choices

Due to the increasing role of energy costs and growing heat density of servers, cooling issues are becoming very
challenging and very important. While it is commonly accepted that power consumption is the number one challenge for
future HPC systems, people often focus on the power consumed by the compute hardware only, often leaving aside the
necessary increase in cooling power, which is required for more densely packaged, highly integrated hardware. The
information presented herein is a result of data analysed and collected in a process of distributing a detailed survey
among PRACE partners. In the paper we go into particulars of the cooling area by presenting different technologies and
devices currently used in modern HPC data centres. We also try to describe innovative and promising solutions adopted
by some PRACE partners that may pave the way for future standards. We focus on highlighting all advantages and
disadvantages of each described solution. In the final part we try to provide general recommendations for HPC centres
required to be taken into account when building an appropriate cooling system.