ATLAS computing challenges before the next LHC run

ATLAS software and computing is in a period of intensive evolution. The current long shutdown presents an opportunity to assimilate lessons from the very successful Run 1 (2009-2013) and to prepare for the substantially increased computing requirements for Run 2 (from spring 2015). Run 2 will bring a near doubling of the energy and the data rate, high event pile-up levels, and higher event complexity from detector upgrades, meaning the number and complexity of events to be analyzed will increase dramatically. At the same time operational loads must be reduced through greater automation, a wider array of opportunistic resources must be supported, costly storage must be used with greater efficiency, a sophisticated new analysis model must be integrated, and concurrency features of new processors must be exploited. This paper surveys the distributed computing aspects of the upgrade program and the plans for 2014 to exercise the new capabilities in a large scale Data Challenge.