  We present the 8th Full Focal Plane simulation set (FFP8), deployed in
support of the Planck 2015 results. FFP8 consists of 10 fiducial mission
realizations reduced to 18144 maps, together with the most massive suite of
Monte Carlo realizations of instrument noise and CMB ever generated, comprising
$10^4$ mission realizations reduced to about $10^6$ maps. The resulting maps
incorporate the dominant instrumental, scanning, and data analysis effects;
remaining subdominant effects will be included in future updates. Generated at
a cost of some 25 million CPU-hours spread across multiple
high-performance-computing (HPC) platforms, FFP8 is used for the validation and
verification of analysis algorithms, as well as their implementations, and for
removing biases from and quantifying uncertainties in the results of analyses
of the real data.
