CONCEPT - Shortest Seek Time First (SSTF)

Algorithm


Shortest Seek Time First(SSTF)

In SSTF, requests having shortest seek time are executed first. So, the seek time of every request is calculated in advance in the queue & then they are scheduled according to their calculated seek time. So, request near the disk arm will get executed first.

    Advantages:

  • Average Response Time Decreases and Throughput Increases

    • DisAdvantages:

  • Overhead to calculate seek time in advance
  • Can cause Starvation for a request which has higher seek time

Example:

Suppose the order of request is- (82,170,43,140,24,16,190)
And current position of Read/Write head is : 50

So, total seek time:
= (50-43)+(43-24)+(24-16)+(82-16)+(140-82)+(170-40)+(190-170)
= 208