Solving some Mysteries in Power Monitoring of Servers: Take Care of your Wattmeters!

International audienceLarge-scale distributed systems (e.g., datacenters, HPC systems, clouds, large-scale networks) consume and will consume enormous amounts of energy. Therefore, accurately monitoring the power and energy consumption of these systems is more and more unavoidable. The main novelty of this contribution is the analysis and evaluation of different external and internal power monitoring devices tested using two different computing systems, a server and a desktop machine. Furthermore, we also provide experimental results for a variety of benchmarks which exercise intensively the main components (CPU, Memory, HDDs, and NICs) of the target platforms to validate the accuracy of the equipment in terms of power dispersion and energy consumption. This paper highlights that unlike to external wattmeters, internal wattmeters do no register neither an equal energy consumption nor a similar power dispersion. Thanks to the high sampling rate and to the different measured lines, the internal wattmeters allow to better visualize some power fluctuations. However, a high sampling rate is not always necessary to understand the evolution of the power consumption during the execution of a benchmark