Apr 1, 2000
New Capabilities in the HENP Grand Challenge Storage Access System
and its Application at RHIC
- Lawrence Berkeley National Laboratory
- Brookhaven National Laboratory
- Argonne National Laboratory
The High Energy and Nuclear Physics Data Access Grand Challenge
project has developed an optimizing storage access
software system that was prototyped at RHIC.
It is currently undergoing integration with the STAR experiment
in preparation for data taking that starts in mid-2000.
The behavior and lessons learned in the RHIC Mock Data Challenge
exercises are described as well as the observed performance
under conditions designed to characterize scalability. Up to
100 simultaneous queries were tested and up to 10 M events across
7 event components were involved in these queries. The system
coordinates the staging of "bundles" of files from the HPSS
tape system, so that all the needed components of each event
are in disk cache when accessed by the application software.
The caching policy algorithm for the coordinated
bundle staging is described in the paper.
The initial prototype implementation interfaced to the Objectivity/DB.
In this latest version, it evolved to work with ROOT files
and use CORBA interfaces to the tag database and file catalog services.
The interface to the ROOT-based event data, tag database and the
MySQL-based file catalog services used by STAR are
described along with the planned usage scenarios.