During operations, NOvA produces between 5,000 and 7,000 raw files per day with peaks in
excess of 12,000. These files must be processed in several stages to produce fully calibrated
and reconstructed analysis files. In addition, many simulated neutrino interactions must
be produced and processed through the same stages as data. To accommodate the large
volume of data and Monte Carlo, production must be possible both on the Fermilab grid
and on off-site farms, such as the ones accessible through the Open Science Grid.
To handle the challenge of cataloging these files and to facilitate their off-line processing,
we have adopted the SAM system developed at Fermilab. SAM indexes files according to
metadata, keeps track of each file’s physical locations, provides dataset management facilities,
and facilitates data transfer to off-site grids.
To integrate SAM with the Fermilab’s ART software framework and the NOvA production
workflow, we have developed methods to embed metadata into our configuration files, ART
files, and standalone ROOT files. A module in the ART framework propagates the embedded
information from configuration files into ART files, and from input ART files to output ART
files, allowing us to maintain a complete processing history within our files. Embedding
metadata in configuration files also allows configuration files indexed in SAM to be used as
inputs to Monte Carlo production jobs. Further, SAM keeps track of the input files used
to create each output file. Parentage information enables the construction of self-draining
datasets which have become the primary production paradigm used at NOvA. We will
present an overview of SAM at NOvA and how it has transformed the file production
framework used by the experiment.
