  Current state-of-the-art simulations of accretion flows onto black holes
require a significant level of numerical sophistication, in order to allow the
three-dimensional modelling of relativistic magnetised plasma in a regime of
strong gravity. We present here a new version of the GRMHD code \texttt{ECHO}
developed in collaboration with the Max Planck Computing and Data Facility
(MPCDF) and the Leibniz Rechenzentrum (LRZ), which employs a hybrid
multidimensional MPI-OpenMP coupled with the production of MPI-HDF5 output
files. The code's high degree of parallelisation has been crucial for the study
of some fundamental properties of thick accretion disks around black holes, in
particular the excitation of non-axisymmetric modes in presence of both
hydrodynamic and magnetohydrodynamic instabilities.
