Question

Consider a disk queue with requests for I/O to blocks on cylinders: 71,146,32,90,45,24,161,75 and 63. If the disk head initially is at cylinder 83 list in which order the SSTF algorithm would visit these cylinders!

Answer 1

The SSTF algorithm selects the request with the shortest seek time from the current position of the disk head. The order in which the algorithm would visit the cylinders, starting from cylinder 83, is 75, 71, 63, 45, 32, 24, 90, 146, and 161.

Step-by-step explanation:

The SSTF (Shortest Seek Time First) algorithm selects the request with the shortest seek time from the current position of the disk head. In this case, the disk head initially starts at cylinder 83.

By calculating the seek time for each request relative to the current position of the disk head, we can determine the order in which the SSTF algorithm would visit the cylinders:

1. The nearest cylinder to 83 is 75 with a seek time of 8.
2. The next nearest cylinder to 75 is 71 with a seek time of 4.
3. The next nearest cylinder to 71 is 63 with a seek time of 8.
4. The next nearest cylinder to 63 is 45 with a seek time of 18.
5. The next nearest cylinder to 45 is 32 with a seek time of 13.
6. The next nearest cylinder to 32 is 24 with a seek time of 8.
7. The next nearest cylinder to 24 is 90 with a seek time of 94.
8. The next nearest cylinder to 90 is 146 with a seek time of 56.
9. The next nearest cylinder to 146 is 161 with a seek time of 15.

So, the order in which the SSTF algorithm would visit the cylinders is: 75, 71, 63, 45, 32, 24, 90, 146, and 161.