Mr Igor Sfiligoi (University of California San Diego)
The User Analysis of the CMS experiment is performed in distributed way using both Grid and dedicated resources. In order to insulate the users from the details of computing fabric, CMS relies on the CRAB (CMS Remote Analysis Builder) package as an abstraction layer. CMS has recently switched from a client-server version of CRAB to a purely client-based solution, with ssh being used to interface with either HTCondor or glideinWMS batch systems. This switch has resulted in significant improvement of user satisfaction, as well as in significant simplification of the CRAB code base. This paper presents the architecture of the ssh-based CRAB package, the rationale behind it, as well as the operational experience running both the client-server and the ssh-based versions in parallel for several months.
Ian Fisk (Fermi National Accelerator Lab. (US))