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CS439: Principles of Computer Systems

Homework 8, Part 1

Due: 8:45a Friday, April 3, 2015

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

  1. The MegaGiga hard disk rotates at 5400 rpm with an arm seek time given by = 4 + 0.05t msec, where t is the number of tracks the arm seeks. Assume a block size of 512 bytes, and 1024 tracks with 512 blocks/track, and 2 platters with 4 usable surfaces. The disk controller and DMA read or write data from/to disk at a rate of 4MB/sec. What is the storage capacity of the disk?
  2. Question 6.3, page 575, B&O. Note that the book calculates transfer time differently than we did in class. If you are not given the transfer rate, theirs is the method to use.

  3. 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.

  4. Assume a spinning disk. Where on that disk would you place the inode array? Justify your answer.

  5. Jane would like to append data to the file /usr/jane/classes/cs439/exam_study_notes.txt. Assuming she has the correct permissions, describe the steps the operating system would need to take to append the data.