Consider a disk system having 60 cylinders. Disk requests are received by a disk drive for cylinders 10, 22, 20, 2, 40, 6, and 38, in that order. Assuming the disk head is currently at cylinder 20, what is the time taken to satisfy all the requests if it takes 2 milliseconds to move from one cylinder to an adjacent one and Shortest Seek Time First (SSTF) algorithm is used ?
120 milliseconds
SSTF serves the requests in the order 20 → 22 → 10 → 6 → 2 → 38 → 40. The total movement is 0 + 2 + 12 + 4 + 4 + 36 + 2 = 60 cylinders. At 2 milliseconds per cylinder, the total seek time is 120 milliseconds.
Important Questions from Disk Scheduling - Teaching
Disc is divided into several concentric circles called _______.
A disc consists of ______, ______, ______.
The total storage capacity of a floppy disk having 80 tracks and storing 128 bytes/sector is 163,840 bytes. How many sectors does this disk have?
In _______ disk scheduling algorithm, the disk head moves from one end to other end of the disk, serving the requests along the way. When the head reaches the other end, it immediately returns to the beginning of the disk without serving any requests on the return trip.
