Open source computing clusters for scientific purposes are growing in size, complexity and eterogeneity; often they are also included in some geographically distributed computing GRID. In this framework the difficulty of assessing the overall efficiency, identigying the bottlenecks and tracking the failures of single components is increasing continously. In previous works we have formalized and proposed a set of metrics to make such an evaluation and built an analysis and simulation infrastructure to find a quantitative measure of the efficiency of a TORQUE/Maui based system. The analysis presented in this work is based on the comparison of real data and simulated data, the latter assumed as maximum theoretical limit.