An adaptive UNIX disk device driver is described. To reduce seek times, the driver copies frequently-referenced blocks from their original locations to reserved space near the center of the disk. Block reference frequencies need not be known in advance. Instead, they are estimated by monitoring the stream of arriving requests. Measurements show that the adaptive driver reduces seek times and response times substantially. © 1997 by John Wiley & Sons, Ltd.

Safe RAM is RAM which has been made as reliable as a disk. We consider the problem of buffer management in partially safe buffers, i.e., buffers which contain both safe RAM and volatile RAM. Buffer management techniques for partially safe buffers explicitly consider the safety of memory in deciding which data to place in the buffer, where to place it, and when to copy updates back to the disk. We present techniques for managing such buffers and study their performance using trace-driven simulations.>

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.

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 center of the disk. Reference frequencies need not be known in advance. Instead, they are estimated by monitoring the stream of arriving requests. Results of 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 is designed to be implemented in a device driver or controller. It is independent of the file system or database manager that uses the disk.>