System Software and Operating System - File and Input/Output System
- Option : D
- Explanation : Time taken to access one block = seek time + rotational delay + block transfer time
Seek time = 20 ms (given)
Rotational delay = on an average taken to be the time to rotate by half = 1/2 X time for 1 rotation = 1/2 X 1/20 seconds = 1/40 s = 25 ms
Block Transfer time = block size / transfer rate = 100 / transfer rate
Now, transfer rate = Track capacity / rotation rate = 300 / ( 1/ 20) = 6000 word per sec = 6 word per ms
Block Transfer time = block size / transfer rate = 100 / 6 ~ 16.67 ms per block Time taken to access one block = seek time + rotational delay + block transfer time= 20 + 25 + 16.67 = 61.67 ms
- Option : B
- Explanation : Shortest Seek Time First - minimizes arm movement
Order to be followed is - (20) , 18,25,35,39, 8,5,3
Seek = 2+5+7+10+4+31+3+2 = 59 cylinders , 295 ms
- Option : B
- Explanation : According to FCFS order serverd will be (20),10, 22, 20, 2, 40, 6 and 38
Seek time = 10+12+2+18+38+34+32 = 146
The disk drive has to traverse totally 146 cylinders (verify). So, seek time is 6 x 146 = 876 ms.
