Experience with the CMS Computing Model from commissioning to collisions

In this presentation we will discuss the early experience with the CMS computing model from the last large scale challenge activities through the first six months of data taking. Between the initial definition of the CMS Computing Model in 2004 and the start of high energy collisions in 2010, CMS exercised the infrastructure with numerous scaling tests and service challenges. We will discuss how those tests have helped prepare the experiment for operations and how representative the challenges were to the early experience with data taking. We will outline how the experiment operations has evolved during the first few months of operations. The current state of the Computing system will be presented and we will describe the initial experience with active users and real data. We will address the issues that worked well in addition to identifying areas where future development and refinement is needed.