Access time based on initial head position in disk scheduling

Abstract

As we know that most of the job in computeris performed on the basis of job scheduling algorithm
by disk access. The basic parameter of all thesealgorithm is head movement. The criteria for best
algorithm is minimum head movement to perform thesame job, whether algorithm used to perform job is
LOOK or C-LOOK or C-SCAN or SCAN or SSTF orFIFO. Most jobs in computer depend heavily on disk
access. But now, question arises “How to improve diskaccess time?” This can be done by scheduling the
request for disk access for operating system. If thedesired disk drive and controller are available the
access can be immediately. in any system when the driveis operating, the disk is rotates at constant speed. To
read or write, the head must be positioned at thedesired track and at the beginning of the desired sector
on that track. Track selection involves moving the headin a movable-head system.
The performance of disk schedulers is affectedby many factors such as initial head position,
workloads, file systems, and disk systems. Diskscheduling performance can be improved by positioning
the Read/Write Heads at appropriate position.Scheduler performance tuning is mostly done manually.
To automate this process, we propose initial headposition in disk scheduling schemes. We conducted
experiments to compare the performance and overheadof algorithms.
In this paper, we are going to study or analyzeFIFO, SSTF or SCAN algorithm on the basis of
increasing the range of head position from 0 - 200 to 0 -500 because all these algorithms are analyzed
previously on the basis of range from 0- to 200 whetherit is done by using IBM’s disk or HP disk.