Disk head scheduling is a standard topic in undergraduate operating systems courses. Disk drives were once fairly simple devices with little intelligence. Disk head scheduling and bad block mapping were done exclusively by operating systems. As disk drives became larger and faster, they took on some of these tasks. Modern drives often have a large cache and hide their internal structure from the outside world. In spite of changes in disk technology, the teaching of disk head scheduling has changed little over the last decade. This paper describes a disk head scheduling simulator that allows students to explore traditional disk scheduling algorithms as well as the consequences of modern disk technology. The simulator, which is written in Java and is freely available, can be run remotely from a browser or downloaded for local execution. We present methods for modifying the traditional curriculum to make the presentation of disk head scheduling more relevant and interesting.
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