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CS439: Principles of Computer Systems

Homework 8, Part 1

Due: 9:45a Thursday, October 29, 2015

Part 1 of the homeworks must be submitted electronically. Please refer to the homework turnin instructions.

  1. Question 9.19, page 852 in the Second Edition, page 880 in the Third Edition, B&O.

  2. Disk requests come into the disk driver for tracks 10, 22, 20, 2, 40, 6, and 38, in that order. A seek takes 6 msec per track moved. How much seek time is needed for the following scheduling algorithms?
    a) FIFO
    b) SSTF
    c) LOOK (SCAN, but doesn't move to the end)
    In all cases, the arm is initially at track 20, and you may assume that the head is traveling towards higher numbers.

    Adapted from Tannenbaum Chapter 5 Number 24.

  3. Suppose I have a disk such as the 320GB SATA drive described here and I have a workload consisting of 10,000 reads to sectors randomly scattered across the disk. How long will these 10,000 request take (total) assuming the disk services requests in FIFO order?

  4. Some file allocation schemes limit the size of the file whether or not there is enough space for a larger file. Which ones and why?
    1. Linked
    2. Direct
    3. Contiguous
    4. Multi-Level index
    5. Extents

  5. How does a journaling file system maintain file system consistency even in the event of a crash? Name an example of a journaling file system.