Experience with CMS Offline and Computing from Commissioning to Collisions

Abstract

In this presentation we will discuss the early experience with the CMS computing model from the last large scale challenge activities through the early collisions runs. Between the initial definition of the CMS Computing Model in 2004 and the start of high energy collisions in 2010, CMS exercised numerous scaling tests. We will discuss how those tests have helped prepare the experiment for operation. We will outline how the experiment operation has evolved during the first few months of operation. The current state of the Offline and Computing projects will be presented and we will describe the initial experience with active analysis users and real data. We will include Tier0 processing, reprocessing steps on data and fast turn-around calibrations. We will address the issues that worked well in addition to identifying areas where future development and refinement are needed.