Inhaltszusammenfassung:
With the ever-growing amount of data collected with the experiments at the
Large Hadron Collider (LHC) (Evans et al., 2008), the need for computing resources
that can handle the analysis of this data is also rapidly increasing. This
increase will even be amplified after upgrading to the High Luminosity LHC
(Apollinari et al., 2017). High-Performance Computing (HPC) and other cluster
computing resources provided by universities can be useful supplements to the
resources dedicated to the experiment as part of the Worldwide LHC Computing
Grid (WLCG) (Eck et al., 2005) for data analysis and production of simulated
event samples. Computing resources in the WLCG are structured in four layers
– so-called Tiers. The first layer comprises two Tier-0 computing centres
located at CERN in Geneva, Switzerland and at the Wigner Research Centre
for Physics in Budapest, Hungary. The second layer consists of thirteen Tier-1
centres, followed by 160 Tier-2 sites, which are typically universities and other
scientific institutes. The final layer are Tier-3 sites which are directly used by
local users. The University of Freiburg is operating a combined Tier-2/Tier-3,
the ATLAS-BFG (Backofen et al., 2006). The shared HPC cluster »NEMO« at
the University of Freiburg has been made available to local ATLAS (Aad et al.,
2008) users through the provisioning of virtual machines incorporating the ATLAS software environment analogously to the bare metal system at the Tier-3. In
addition to the provisioning of the virtual environment, the on-demand integration
of these resources into the Tier-3 scheduler in a dynamic way is described. In
order to provide the external NEMO resources to the user in a transparent way,
an intermediate layer connecting the two batch systems is put into place. This
resource scheduler monitors requirements on the user-facing system and requests
resources on the backend-system.
Particle Physics