The Atropos logical volume manager allows applications to exploit characteristics of its underlying collection of disks. It stripes data in track-sized units and explicitly exposes the boundaries, allowing applications to maximize efficiency for sequential access patterns even when they share the array. Further, it supports efficient diagonal access to blocks on adjacent tracks, allowing applications to orchestrate the layout and access of two-dimensional data structures, such as relational database tables, to maximize performance for both row-based and column-based accesses. We thank the members and companies of the PDL Consortium (including EMC, Hewlett-Packard, Hitachi, IBM, Intel, Microsoft, Network Appliance, Oracle, Panasas, Seagate, Sun, and Veritas) for their interest, insights, feedback, and support. This work is funded in part by NSF grants Many storage-intensive applications, most notably database systems and scientific computations, have some control over their access patterns. Wanting the best performance possible, they choose the data layout and access patterns they believe will maximize I/O efficiency. Currently, however, their decisions are based on manual tuning knobs and crude rules of thumb. Application writer
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