Grid-based Production

PDSF is a Tier 2 site for ALICE and as such has the infrastructure in place to run automated grid-based ALICE production jobs.  The main components of this infrastructure are listed below.

Grid-Enabled Storage Elements

There are currently a set of 5 servers running XRootD with a total capacity of 350TB.  Included in XRootD are the data transfer tools used to transfer the input and output files for the production jobs running at PDSF.  In addition to the 5 servers there is also the XRootD redirector which is currently running on pc1801.nersc.gov (pdsf5.nersc.gov).

VO Box

A VO (Virtual Organization) box is a dedicated node (palicevo1.nersc.gov) that coordinates the production.  It runs the grid-monitoring tool MonALISA, the AliEn grid framework software, a Condor-G client and does job submissions.  While the VO box sends and receives the necessary information to coordinate the production it does not transfer data files.  This is done by XRootD as noted above.  The MonALISA information for ALICE can be viewed here.

Grid Accounting

The actual job submissions go through the PDSF grid gatekeeper (pdsfgrid.nersc.gov) which has the Open Science Grid (OSG) software installed.  Included in this software is Gratia which is software developed by OSG for collecting accounting information on grid jobs.  Gratia reports the accounting information for the ALICE jobs to OSG which in turn reports the information to the Worldwide LHC Computing Grid (WLCG).