1. Introduction to Disk Scheduling:

Disk scheduling is crucial for optimizing the order in which read and write requests are serviced from a disk. SSTF is an advanced disk scheduling algorithm designed to minimize the seek time by selecting the request with the shortest seek time first.

2. SSTF Disk Scheduling Algorithm:

Working:

Maintain a queue of disk requests.

Choose the request with the shortest seek time from the current head position.

Service the selected request.

Update the current head position.

Repeat the process until all requests are serviced.

Advantages:

Minimizes seek times, improving overall disk performance.

Reduces the effect of the "elevator" problem seen in FCFS.

Disadvantages:

May lead to starvation for requests at the outer or inner tracks.

3. Example Scenario:

Consider disk requests for sectors 30, 25, 35, 20, and 40, and the disk head initially positioned at sector 30.

SSTF:

Initial position: 30

Service order: 30 → 35 → 40 → 25 → 20

4. Conclusion:

SSTF is a sophisticated disk scheduling algorithm that minimizes seek times by selecting the request with the shortest seek time first. While it significantly improves disk performance, it may still suffer from potential starvation for requests at certain tracks.

Notes From The Slides:

SSTF

Shortest Seek Time First selects the request with the minimum seek time from the current head position
SSTF scheduling is a form of SJF scheduling; may cause starvation of some requests
Illustration shows total head movement of 236 cylinders