IS215 - File and Disk Management Exercises - 2

11. What method of ensuring file systems reliability is suitable for each of the following 'file system:

a) small in size and data loss is tolerable (quite cheap to recover)
b) small and data loss are very expensive, hence it should be avoided
c) large in size and data loss is tolerable
d) large in size and data loss is very expensive

Explain your answer.

12. Periodic dump is expensive. Explain.

13. Discuss the procedure for recovering from file system crash, when the system used is a combination of periodic dump, incremental dump and transaction logging.

14. Name an actual system that uses the directory structure:

a) single-level directory
b) two-level directory structure
c) tree-structured directory
d) acyclic directory

15. Discuss a method of checking the consistency of a file system.

16. During file system recovery after a crash, files are often compacted into contiguous regions on the disk even though such contiguity may be irrelevant to the file access method. Explain why compaction may still be advantageous.

17. Given the following requests for disk access in a disk whose tract number ranges from 0 to 99.

20, 7, 99, 56, 75, 19, 89, 2, 50

The read/write head is currently reading track number 15 and has just gone from track number 26, if the scheme used is:

a) First-Come-First-Serve
b) Shortest-Seek-Time-First
c) SCAN
d) CSCAN
e) N-Step SCAN

18. Differentiate non-contiguous sector allocation from non-contiguous block allocation.

19. What are the overheads involved with the allocation strategies: contiguous, linked, 'and indexed, if the file:

a) grows at the beginning
b) grows at the middle
c) grows at the end?

Answer also the cases when the file shrinks instead of grows.

20. All the disk scheduling algorithms (SSTF, SCAN, C-SCAN, N-Step SCAN) except FCFS are not truly fair (starvation may occur). Arrange the algorithms in order of degrading fairness. Show how you arrived at your answer.

IS215 - File and Disk Management Exercises - 1

1. What is a file? Describe the three most common file organizations.

2. What is a file descriptor? What is a file directory? What is the relationship between the two?

3. What is the difference of a tree-structured directory structure from an acyclic directory structure?

4. Suppose a computer system will be used for software development of a programming team.

a) What directory system is suited for this type of system?
b) What file protection scheme is needed to satisfy the needs of the users?
c) What file access methods should be supported?
d) What file allocation method should be used?

Answer the same questions for system intended as an automated teller machine (ATM).

5. Identify the minimal operations on files that will allow all other operations to be simulated using the operations in the minimal set operations.

6. One way of protecting the file system is through the use of passwords. Why is this method not used anymore in most modern operating systems?

7. Outline a method of protecting the files of a user in a multi-user operating system. The method should allow others to access the files of the user if he allows it.

8. What are the advantages of direct access to files over the sequential access to files? Are both access methods really necessary in an operating system?

9. What is the difference between sector and block file allocation methods? Is there a situation where both methods are one and the same?

10. What is the problem in contiguous allocation method that is solved by the linked allocation method?