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High-performance I/O systems depend on prefetching and caching in order to deliver good performance to applications. These two techniques have generally been considered in iso-lation, even though there are signicant interactions between them; a block prefetched too early reduces the eectiveness of the cache, while a block cached too long reduces the ef-fectiveness of prefetching. In this paper we study the ef-fects of several combined prefetching and caching strategies for systems with multiple disks. Using disk-accurate trace-driven simulation, we explore the performance characteristics of each of the algorithms in cases in which applications pro-vide full advance knowledge of accesses using hints. Some of the strategies have been published with theoretical per-formance bounds, and some are components of systems tha