In preparation for the data collection and analysis in LHC Run 2, the LHCC and Computing Scrutiny Group of the RRB requested a detailed review of the current computing models of the LHC experiments and a consolidated plan for the future computing needs. This document represents the status of the work of the WLCG collaboration and the four LHC experiments in updating the computing models to reflect the advances in understanding of the most effective ways to use the distributed computing and storage resources, based upon the experience gained during LHC Run 1.
The paper tries to give an overview of technology and market trends in computing. The final goal of this exercise is to provide essential input for the budget and resource planning of the CERN computer centre. These CERN technology and market investigations are done in a general way, but need to take into account the boundary conditions coming from the High Energy Physics community and the CERN infrastructure.