CernVM – a virtual software appliance for LHC applications

CernVM is a Virtual Software Appliance capable of running physics applications from the LHC experiments at CERN. It aims to provide a complete and portable environment for developing and running LHC data analysis on any end-user computer (laptop, desktop) as well as on the Grid, independently of Operating System platforms (Linux, Windows, MacOS). The experiment application software and its specific dependencies are built independently from CernVM and delivered to the appliance just in time by means of a CernVM File System (CVMFS) specifically designed for efficient software distribution. The procedures for building, installing and validating software releases remains under the control and responsibility of each user community. We provide a mechanism to publish pre-built and configured experiment software releases to a central distribution point from where it finds its way to the running CernVM instances via the hierarchy of proxy servers or content delivery networks. In this paper, we present current state of CernVM project and compare performance of CVMFS to performance of traditional network file system like AFS and discuss possible scenarios that could further improve its performance and scalability.