Adaptive block rearrangement

Abstract

An adaptive technique for reducing disk seek times is described. The technique copies frequently referenced 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 substantially 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 that uses the driver.