WLCG Service Challenges and Tiered architecture in the LHC era

The implementation of the computing infrastructure for LHC experiments requires graduate and accurate verification of performance of hardware resources (CPU, storage, network), of the middleware services provided by Grid projects and of the LHC experiment-specific software applications. The realization of the Computing Models of the LHC experiments needs high reliability of resources and services, and the demonstration of their functionality, robustness and effective usability in addressing real experiment use-cases. The data management and workload management sector of the Computing Models of LHC experiments are tested both in experiment-specific “Data Challenges” and in more general “Service Challenges” of increasing complexity, the latter being driven by Worldwide LHC Computing Grid (WLCG). The objective is to improve the quality and reliability of the distributed Grid services to address the computing needs in the LHC era.