Speaker
Dr
Joel Snow
(Langston University)
Description
Periodically an experiment will reprocess data taken previously to take advantage of
advances in its reconstruction code and improved understanding of the detector.
Within a period of ~6 months the DØ experiment has reprocessed, on the grid, a large
fraction (0.5fb-1) of the Run II data. This corresponds to some 1 billion events or
250TB of data and used raw data as input, requiring remote database access. This is
the largest HEP grid activity and has been a great success. SAM (Sequential Access to
Metadata) has been in operation at DØ since the start of Run II and provides the
data-grid (also enabling remote analysis). Job submission and management is provided
by JIM. Together they form the middleware SAM-Grid, used for this activity. This
massive task led to extensive developments in SAM-Grid, in a joint effort between the
core developers and those carrying out the reprocessing at the remote sites. The
resources used, corresponding to some 3500 GHz equivalent, were shared and include
LCG and OSG facilities. This activity, including the development of SAM-Grid and the
operational tools and procedures developed will be presented. Lessons learnt from
carrying out such a task on the grid will be discussed.
Primary author
Dr
Gavin Davies
(Imperial College London)
Co-authors
Dr
Daniel Wicke
(University of Wuppertal)
Dr
Gabriele Garzoglio
(Fermi National Accelerator Laboratory)
Dr
Mike Diesburg
(Fermi National Accelerator Laboratory)
