CSC 539: Operating Systems Structure and Design
Spring 2005
HW5: I/O, Security & Distributed Systems
- 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?
- FCFS
- SSTF
- SCAN
- LOOK
- C-SCAN
- Is disk scheduling, other than FCFS scheduling, useful in a single-user
environment? Explain
your answer.
- Explain why SSTF scheduling tends to favor middle cylinders over the
innermost and
outermost cylinders.
- What are the various kinds of performance overheads associated with
servicing an interrupt?
- 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.
- What are two main differences between a WAN and a LAN?
- What is the difference between computation migration and process
migration? Which is easier to implement, and why?
- AFS is designed to support a large number of clients. Discuss three
techniques used to make AFS a scalable system.
- Describe three (3) fundamental differences between AFS and NFS.
- Why is deadlock detection much more expensive in a distributed environment
than it is in a centralized environment?