Assignment 6

Due Wednesday, April 1, 2015 6:00 pm via sakai


Please answer the questions concisely. The answer to the first two questions might be a couple of sentences but all others can be answered with a short sentence or a short list. You will get no credit for long winded answers.


Please remember to submit your assignment as plain text, in-line HTML on sakai, or pdf (if necessary) only. You will get no credit and no second chance to resubmit any Microsoft Word, Apple Pages, or other formats that will require me to run an application to read your submission.

Pay attention to the deadline and strive to get your submission well before that time to allow for any last-minute glitches. No extensions will be given.


  • Read Chapter 9
    • Sections 9.1 - 9.2, pages 441-445.
    • Sections 9.4 - 9.5.1, pages 446-454.
  • Chapter 10
    • Sections 10.0 - 10.1.5, pages 477-487.
    • Sections 10.3.2-10.3.5, pages 493-496.
    • Section 10.4, pages 500-502.
  • Chapter 11
    • Sections 11.1-11.5.2, pages 517-536.
    • Sections 11.6-11.6.2, pages 538-542.

Read the section on Plan 9 union directories in this document:


  1. [9.11] Suppose that a disk drive has 5,000 cylinders, numbered 0 to 4999. The drive is currently serving a request at cylinder 2150, and the previous request was at cylinder 1805. The queue of pending requests, in FIFO order, is: 2069, 1212, 2296, 2800, 544, 1618, 356, 1523, 4965, 3681 Starting from the current head position, what is the total distance (in cylinders) that the disk arm moves to satisfy all the pending requests for each of the following disk-scheduling algorithms?
    a. FCFS
    b. SSTF
    c. SCAN
    d. LOOK
    e. C-SCAN
  2. Explain how a union mount differs from a conventional file system mount.
  3. How can union directories remove the need for a PATH environment variable (which contains a list of directories that the shell will search for executable files)?
  4. [11.11] What are the advantages of the variation of linked allocation that uses a FAT to chain together the blocks of a file?
  5. [11.16] Consider a file system that uses inodes to represent files. Disk blocks are 8 KB in size and a pointer to a disk block requires 4 bytes. This file system has 12 direct disk blocks, plus one each of single, double, and triple indirect disk blocks. What is the maximum size of a file that can be stored in this file system?