  In October 2013 CSCS installed the first hybrid Cray XC-30 system, dubbed Piz
Daint. This system features the power management database (PMDB), that was
recently introduced by Cray to collect detailed power consumption information
in a non-intrusive manner. Power measurements are taken on each node, with
additional measurements for the Aries network and blowers, and recorded in a
database. This enables fine-grained reporting of power consumption that is not
possible with external power meters, and is useful to both application
developers and facility operators. This paper will show how benchmarks of
representative applications at CSCS were used to validate the PMDB on Piz
Daint. Furthermore we will elaborate, with the well-known HPL benchmark serving
as prototypical application, on how the PMDB streamlines the tuning for optimal
power efficiency in production, which lead to Piz Daint being recognised as the
most energy efficient petascale supercomputer presently in operation.
