First Experiences with CMS Data Storage on the GEMSS System at the INFN-CNAF Tier-1

A brand new Mass Storage System solution called “Grid-Enabled Mass Storage System” (GEMSS) -based on the Storage Resource Manager (StoRM) developed by INFN, on the General Parallel File System by IBM and on the Tivoli Storage Manager by IBM -has been tested and deployed at the INFNCNAF Tier-1 Computing Centre in Italy. After a successful stress test phase, the solution is now being used in production for the data custodiality of the CMS experiment at CNAF. All data previously recorded on the CASTOR system have been transferred to GEMSS. As final validation of the GEMSS system, some of the computing tests done in the context of the WLCG “Scale Test for the Experiment Program” (STEP’09) challenge were repeated in September-October 2009 and compared with the results previously obtained with CASTOR in June 2009. In this paper, the GEMSS system basics, the stress test activity and the deployment phase -as well as the reliability and performance of the system -are overviewed. The experiences in the use of GEMSS at CNAF in preparing for the first months of data taking of the CMS experiment at the Large Hadron Collider are also presented.