CS 161: Operating Systems

Tuesday/Thursday 1:00-2:30

Pierce 301

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Web Work Answers

Below are our solutions to the web work, along with explanations as to why we think they are correct. Note that some of the questions are ambiguous and can be interpreted several ways, some of which yield other, equally correct answers. If you're unsure of your understanding of the material and want to know whether your answer was also correct, or if you feel like our solution is incorrect, feel free to reach out to the course staff. However, the web work is graded only on completion, not on exactly matching the solutions below, so there's no need to argue your case if you're confident you're also right.


1. Which of the following pieces of existing code do you expect you will need to modify in Assignment 4?
2. Which of the following is not necessary to do to use an SFS file system?
3. Prior to adding journaling, SFS maintains consistency via synchronous ordered writes.
False! It doesn't maintain consistency at all.
4. If you unmount an SFS volume and then run sfsck, you should not get any errors.
5. 5. Which of the following seem like record types you might need to support in this assignment?
6. How many different record types can you have in an OS/161 journal?
7. What do we call the unique identifier we use to refer to a log record?
Log Sequence Number, LSN
8. Which of the following are tools or programs that can be used to test your file system?
sfsck, The DOom Counter, frack, poisondisk are all good test features; mksfs simply makes a file system, something you'll have to do, but isn't really a test feature. And crashme isn't a program we give you.
9. New records in jphys appear at the HEAD or the TAIL?
10. Is it possible to use the physical journal provided in OS/161 to implement multithreaded recovery?
That would be, "No!"
11. Which of the following accurately completes the following statement: A single journal transaction contains ...
Multiple log records from a single high-level file system operations
12. Assuming UNDO/REDO logging, Which of the following log records describe idempotent operations?