Question

NEED ASAP PLEASE WILL GIVE GOOD RATE RIGHT AWAY FOR ALL ANSWERS!

suppose that a disk drive has 500 tracks numbered 0 through 499. the drive is currently servicing a request at track 350 and the previous request was at track 180. the qeue off pending requests in FIFO order is : 206 280 110 160 370

starting ftom the current position what are the next two requests that will be serviced for each of the following disk scheduling algorithms

a) SSTF

B) FCFS

C) SCAN

D) C SCAN

Answer 1

a) Shortest seek time first

the track closer to current disk head position is serviced first.

In this case there are 500 tracks and the drive is at track 350 right now. So the next track would be the one closer to track 350 which would be 370

and the next track would be closer to track 370 which would be 280

so the processing would be in the order

180, 350, 370, 280, 206, 160, 110

b) First come first out

In FCFS, the first element which is in the stack is processed first, so after 350, the track would be 206 which is first in line and the next one would be 280

so the processing would be in order

180, 350, 206, 280, 110, 160, 370

c) SCAN

In SCAN scheduling, it scans down towards the nearest end and then it hits to the other side

In this case, the track is currently in 350, so it move towards 370 which is the nearest end and second it move towards 280 from 370

so the processing order would be

180, 350, 370, 280, 206, 160, 110

d) C-SCAN

C-SCAN is similar to SCAN but when it hits an end it moves to the other end and then starts the processing.

In this case, the track is currently in 350, so the next move would be to 370 which is the nearest end. Now, after reaching the end it moves to the other end which would be 110.

So the processing order would be

180, 350, 370, 110, 160, 206, 280