Question

Requests to access specific cylinders on a disk drive arrive in this order: 24, 20, 4, 40, 6, 38, and 12, and the seek arm is initially located at cylinder 20. If the average seek time is 6 milliseconds, what is the total seek time for the following algorithms:a. First-comeb. first served; c.Closest cylinder next; d. Elevator algorithm

Answer 1

Answer:

The time required to seek using First come,first served algorithm is 876 milliseconds.

The time required to seek using Shortest Seek Time First algorithm is 360 milliseconds.

The time required to seek using LOOK (initialing moving upwards) algorithm is 348 milliseconds.

Explanation:

Part a,b : First-come, first-served:

The order of the cylinders is as 10, 22, 20, 2, 40, 6, 38

10 + 12 + 2 + 18 + 38 + 34 + 32 = 146 cylinders = 876 milliseconds.

ii) Shortest Seek Time First:

The order of the cylinders is as 20, 22, 10, 6, 2, 39, 40

0 + 2 + 12 + 4 + 4 + 36 + 2 = 60 cylinders = 360 milliseconds.

iii) LOOK (initialing moving upwards):

The order of the cylinders is as 20, 22, 38, 40, 10, 6, 2

0 + 2 + 16 + 2 + 30 + 4 + 4 = 58 cylinders = 348 milliseconds.