Disks

Due:
11:00pm, Friday April 22, 2022

Description

For this assignment we will run process related simulators from the textbook supplementary material (source) and answer related questions. A zip file with the simulator programs linked on the assignments page. The README files for each program are in the assignment directory.

Questions

  1. Compute the seek, rotation, and transfer times for the following sets of requests: -a 0, -a 6, -a 7,30,8, and -a 10,11,12,13. Then, do the same requests but change the seek rate to different values: -S 2, -S 4, -S 8, -S 10, -S 40, -S 0.1. How do the times change? Finally, do the same requests again, but this time change the rotation rate rate: -R 0.1, -R 0.5, -R 0.01. How do the times change?

  2. What order should the following request stream -a 7,30,8 be processed in? Run the shortest seek-time first (SSTF) scheduler on this workload: how long should it take (seek, rotation, transfer) for each request to be served?

  3. Run the shortest access-time first (SATF) scheduler on the request stream -a 7, 30, 8. Does it make a difference compared to the SSTF? Secondly, can you find a request stream where SATF performs better than SSTF? If so, write down the request stream you used.

  4. Run some random requests on a multi-zoned disk and compute the seek, rotation, and transfer times. You can specify the angular difference between blocks on the outer, middle, and inner tracks with the -z flag (for example, -z 10, 20, 30). What is the bandwidth (in sectors per unit time) on the outer, middle, and inner tracks?

  5. Generate random workloads (for example, -A 1000,-1,0, with different seeds) and see how long the SATF scheduler takes when the scheduling window is changed from 1 up to the number of requests. How big of a window is needed to maximize performance? Hint: use the -c flag and don’t turn on graphics (-G) to run these quickly. When the scheduling window is set to 1, does it matter which policy you are using?

Turning in the Assignment

Create a text file named assignment9.txt containing your answers to the questions. Submit your solution to the appropriate folder on D2L.

Note that your answers must be correctly numbered and only the answers must be in your submission; any answer solution that does not satisfy these requirements will be marked as a zero.