Abstract

An adaptive technique for reducing disk seek times is described. The technique copies frequentlyreferenced blocks from their original locations to reserved space near the middle of the disk. Reference frequencies need not be known in advance. Instead, they are estimated by monitoring the stream of arriving requests. Trace-driven simulations show that seek times can be cut in half by copying only a small number of blocks using this technique. The technique has been implemented by modifying a Unix device driver. No modifications are required to the file system or database management system that uses the driver. 1 Introduction Because of their relatively long access times, disks can be performance bottlenecks in a storage hierarchy. When data requests arriving at the disk are small and non-sequential, as is common in multi-user operating systems and database systems, seek time is a major component of disk access time [Bitton 87]. This paper presents an adaptive technique for redu...

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