CPSC 461: Copyright © 2002 Katrin Becker 1998-2002 Last Modified October 20, 2001 09:59 PM

FILE SYSTEMS REVIEW QUESTIONS

SHORT ANSWER QUESTIONS

1. [ 2 marks ] On a UNIX system, what is a superblock?
2. [ 4 marks ] In a multi-user system like UNIX, why is it important that reading a directory entry off the disk be an atomic operation?
3. [ 4 marks ] Ignoring personal quota and access requirements, what are the two reasons UNIX might be unable to save a file?
4. [ 3 marks ] What is the biggest file that can be stored on UNIX such that all accesses (after the inode is retrieved) to data file blocks cost at most 1 seek per block? State any assumptions you make.
5. [ 5 marks ] We’ve been told that UNIX maintains multiple copies of the Superblock on a partition as backup in case one is corrupted. If one is corrupted it will be necessary to find one or more of the back-up copies. Explain how this might be accomplished.
6. [ 2 marks ] What is a UNIX 'fragment'?
7. [ 4 marks ] Explain what happens (and why it happens) to performance in UNIX when the disk becomes badly fragmented and someone tries to save a very large file?
8. [ 4 marks ] Is it possible to have sufficient disk space available on a UNIX file System to save a particular file and still be unable to save it? Explain. (typing the command incorrectly doesn't count)
9. [ 2 marks ] Why does Unix use "move mode" for buffering I/O?
10. [ 2 marks ] What is the largest file that can be stored on Unix such that each block written requires at most 1 seek (not counting the inode)
11. [ 2 marks ] If all reads in Unix retrieve 4K bytes, why does Unix allow 2K fragments?
12. [ 4 marks ] What is a UNIX partition?
13. [ 5 marks ] How does UNIX locate the blocks in a file that is 1Mb in size (i.e. where are the pointers to the data blocks and what form do they take)?
14. [ 2 marks ] Name one advantage of using a hard link on UNIX and explain why it is an advantage.
15. [ 2 marks ] Name one advantage of using a soft link on UNIX and explain why it is an advantage.
16. [ 2 marks ] When a file is written to disk in UNIX, who decides on the location of the individual blocks?
17. [ 4 marks ] Using the file structures we have studied in class, describe the structure of UNIX's inodes and the related address blocks.
18. [ 4 marks ] Explain the difference between hard links and symbolic links to files in UNIX.
19. [ 4 marks ] Your UNIX File System has run out of Inodes. How do you fix it?

CPSC 461: Copyright © 2002 Katrin Becker 1998-2002 Last Modified October 20, 2001 09:59 PM