Disk Introduction

This chapter is all about disk. Before we start. We won’t go deep into the mechanical part of disk operation; rather we will be focusing on general concept related to disk and algorithms to improve disk performance.

The Evaluation Criteria

Here we are introducing the basic components used to evaluate the performance of disk operation.

Seek Time

This is the time to position the head over the track. Maximum can be going from innermost track to outer most track. It usually ranges from 10ms to over 20 ms. However, the average seek time is usually to seek 1/3 of the way across the disk.

Head Switch Time

This is time spent to move from one track on one surface to another track on a different surface. The range is similar to seek time.

Rotation Delay

This is the time spend for the sector...