Cut-and-paste Le-systems: Integrating Simulators and Le-systems

We have implemented an integrated and conngurable le system called the Pegasus le-system (PFS) and a trace-driven le-system simulator called Patsy. Patsy is used for oo-line analysis of le-system algorithms, PFS is used for on-line le-system data storage. Algorithms are rst analyzed in Patsy and when we are satissed with the performance results, migrated into PFS for on-line usage. Since Patsy and PFS are derived from a common cut-and-paste le-system framework, this migration proceeds smoothly. We have found this integration quite useful: algorithm bottlenecks have been found through Patsy that could have led to performance degradations in PFS. OO-line simulators are simpler to analyze compared to on-line le-systems because a work load can repeatedly be replayed on the same oo-line simula-tor. This is almost impossible in on-line le-systems since it is hard to provide similar conditions for each experiment run. Since simulator and le-system are integrated (hence, use the same code), experiment results from the simulator have relevance in the real system. This paper describes the cut-and-paste framework, the instantiation of the framework to PFS and Patsy and nally, some of the experiments we conducted in Patsy.