Analysis on disk scheduling for special user functions

Previous studies on disk scheduling for video services were usually based on computer simulation. We present analysis on disk scheduling for video services. This paper first gives a short review on the various disk scheduling algorithms. It then concentrates on the analysis of two major disk scheduling algorithms, namely, CLOOK and LOOK. The purpose of the analysis is to obtain the maximum number of simultaneous users supported by systems using these two algorithms. The results of the analysis show that the CLOOK algorithm performs slightly better than LOOK algorithm in video applications. Then, this paper discusses disk scheduling for supporting special user functions such as "forward search" and "reverse search". It is shown that the maximum number of user streams supported drops dramatically when such user functions are used. A technique called redundancy for special user functions (RESUF) is then studied. Analysis of the technique shows that it can keep the I/O demands to almost constant under all user request conditions.