In this proposal, the PIs describe theWisconsin ProgramAnalysis of Storage Systems project (PASS), and seek to develop the techniques needed to build the high-end, scalable, robust storage systems of tomorrow by bringing a more formal approach to the problem, utilizing programming language tools to build, analyze, test, and monitor these storage systems. By applying these techniques, the PIs plan to raise the level of trust in the failure-handling capabilities of high-end storage systems by an order of magnitude. The PASS project will change the landscape of storage systems in three fundamental ways. First, by developing more formal failure analysis techniques, we will be able to uncover a much broader range of storage system failure handling problems. Second, within PASS we will develop more robust and scalable testing infrastructure; such a framework will be of general use to the development of any future storage system. Finally, through run-time instrumentation of a large Condor cluster, the PIs plan to gather information as to what types of faults occur in practice as well as how they manifest themselves as failures. Such data will be invaluable to future designs and implementations of robust, scalable storage systems.