L. Bernardo et al., New capabilities in the HENP Grand Challenge Storage Access System and itsapplication at RHIC, COMP PHYS C, 140(1-2), 2001, pp. 179-188
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 i
n preparation for data taking that starts in mid-2000. The behavior and les
sons learned in the RHIC Mock Data Challenge exercises are described as wel
l as the observed performance under conditions designed to characterize sca
lability. Up to 250 simultaneous queries were tested and up to 10 million e
vents 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 access
ed by the application software. The caching policy algorithm for the coordi
nated bundle staging is described in the paper. The initial prototype imple
mentation interfaced to the Objectivity/DB. In this latest version, it evol
ved to work with arbitrary files and use CORBA interfaces to the tag databa
se and file catalog services. The interface to the tag database and the MyS
QL-based file catalog services used by STAR are described along with the pl
anned usage scenarios. (C) 2001 Elsevier Science B.V. All rights reserved.