12.1 File System Structure

• What is a file system?
• The textbook lists a six-layer structure for a general file system. Explain what each layer does.
• Why is it better to divide the functions of a file system into multiple layers?

12.2 File System Implementation

• What is a file control block (FCB)? What are some of the common information stored in FCB?
• What is a system-wide open-file table? What information does it contain?
• What is a per-process open-file table? What information does it contain?
• Explain the meaning of Figure 12.3 on page 548.
• What is an inode? What kinds of information does an inode include?
• What is a virtual file system? Why do we need it?

12.3 Directory Implementation

• Explain how a linear list based directory works.
• Explain how a hash table based directory works.

12.4 Allocation Methods

Files are stored as blocks of disk space.

• How does contiguous allocation work?
• How does linked allocation work?
• How does indexed allocation work?
• Explain the inode structure in Figure 12.9
• Pros and cons of each of these methods.
• Compare and contrast these schemes with the ones used in memory management. Differences? Similarities?

12.5 Free Space Management

An OS uses various mechanisms to manage free blocks on disks.

• How does bit-vector work?
• How does linked list work?
• How does grouping work?
• How does counting work?

12.6 Efficiency and Performance

• What is the meaning of efficiency in the file system context?
• How does the block size affect the performance of a file system?
• How does the buffering scheme affect the performance of a file system?
• What does unified buffer cache mean? Why is it better to use unified buffer cache, compared to using separate cache for memory-mapped I/O?