The CERN Analysis Facility - A PROOF cluster for prompt physics analysis

Jan Fiete Grosse-Oetringhaus

The ALICE collaboration (A Large Ion Collider Experiment) at the CERN
LHC plans to use a PROOF (Parallel ROOT Facility) cluster at CERN for
physics analysis. The system design features are especially relevant
for the initial (prototyping) phase of the analysis, which requires a
short response time for a large number of iterations over a
medium-size dataset. Typical examples are the tuning of physics cuts
before analyzing large data samples as well as higher precision
detector calibration and alignment.

Furthermore, the fast response time of the interactive PROOF facility
will enable the ALICE collaboration to extract rapidly physics
observables from the very first events collected at the startup of the
LHC. A test setup consisting of 40 dual-CPU hosts with 8 TB of
distributed disk storage is in operation since May 2006. The PROOF
system enables the parallel processing and xrootd is used to manage
the access to the data. An automatic staging system is used to access
data from the Grid.

This talk will describe the current setup, a few cluster management
aspects as well as the integration of ALICE's software framework
(AliRoot) and user analysis code into PROOF. First experience with
recently introduced features like automatic staging, disk quotas and
CPU fair-share will be presented.