CSC 539: Operating Systems Structure and Design
Spring 2005

HW5: I/O, Security & Distributed Systems

  1. Suppose that a disk drive has 5000 cylinders, numbered 0 to 4999. The drive is currently serving a request at cylinder 143, and the previous request was at cylinder 125. The queue of pending requests, in FIFO order, is 86, 1470, 913, 1774, 948, 1509, 1022, 1750, 130 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?
    1. FCFS
    2. SSTF
    3. SCAN
    4. LOOK
    5. C-SCAN

  2. Is disk scheduling, other than FCFS scheduling, useful in a single-user environment? Explain your answer.

  3. Explain why SSTF scheduling tends to favor middle cylinders over the innermost and outermost cylinders.

  4. What are the various kinds of performance overheads associated with servicing an interrupt?

  5. Argue for or against the judicial sentence handed down against Robert Morris, Jr., for his creation and execution of the Internet worm discussed in Chapter 15.

  6. What are two main differences between a WAN and a LAN?

  7. What is the difference between computation migration and process migration? Which is easier to implement, and why?

  8. AFS is designed to support a large number of clients. Discuss three techniques used to make AFS a scalable system.

  9. Describe three (3) fundamental differences between AFS and NFS.

  10. Why is deadlock detection much more expensive in a distributed environment than it is in a centralized environment?