CSE 120 -- Homework #4

1. Chapter 11: 11.5, 11.9, 11.12

   11.5  What are the advantages and disadvantages of recording the name of the program that creates a file with the file's attributes (as is done in the Macintosh operating system)?

   11.9  Give an example of an application in which data in a file should be accessed in the following order:

      a. Sequentially
      b. Randomly
   

   11.12  Consider a system that supports 5000 users. Suppose that you want to allow 4990 of these users to be able to access one file.

      a. How would you specify this protection scheme in Unix?
      b. Could you suggest another protection scheme that can be used more effectively for this purpose than the scheme provided by Unix?
   

2. Chapter 12: 12.9, 12.10

   12.9  How do caches help improve performance? Why do systems not use more or larger caches if they are so useful?

   12.10  In what situations would using memory as a RAM disk be more useful than using it as a disk cache?

3. [Crowley] A file system is the data structure that holds files and directories.
   • Is it possible to have two file systems on a single physical disk drive? Why or why not?
   • Is it possible to have a file system that spans two physical disk drives? Why or why not?
   • Is it possible to have a file that is not in a file system? Why or why not?
   • The mount operation allows you to graft the directory tree from one file system onto the directory tree of another file system. Does this mean that a file can span both file systems? Why or why not?

4. On a Unix file system, how many disk read operations are required to read the first block of the file "/home/solaris/ieng9/cs120f/file"? Assume that the master block is in memory, but nothing else. Also assume that all directories are one block in size.