Abstract: We introduce range writes, a simple but powerful change to the disk interface that removes the need for file system micromanagement of block placement. By allowing a file system to specify a list of possible address targets, range writes enable the disk to choose which address to write the request to; the disk improves performance by accessing the ``closest'' location and subsequently reporting its choice to the file system above. The result is a clean separation of responsibility; the file system (as high-level manager) provides coarse-grained control over placement, while the disk (as low-level worker) makes the final fine-grained placement decision to improve write performance. We show the benefits of range writes through numerous simulations and a prototype implementation, in some cases improving performance by a factor of three, across both synthetic and real workloads.

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