Update of the Computing Models of the WLCG and the LHC Experiments

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.