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MODERN OPERATING SYSTEMS
Third Edition
ANDREW S. TANENBAUM
Lecture 24: Chapter 4
File Systems
Tanenbaum, Modern Operating ...
Administration
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
• H...
Figure 4-18. Position of the virtual file system.
Virtual File Systems (1)
Tanenbaum, Modern Operating Systems 3 e, (c) 20...
Figure 4-19. A simplified view
of the data structures and
code used by the VFS
and concrete file system
to do a read.
Virt...
Figure 4-20. Percentage of
files smaller than a
given size (in bytes).
Disk Space Management
Block Size (1)
Tanenbaum, Mod...
Figure 4-20. Percentage of
files smaller than a
given size (in bytes).
Disk Space Management
Block Size (2)
Tanenbaum, Mod...
Figure 4-21. The solid curve (left-hand scale) gives the data rate
of a disk. The dashed curve (right-hand scale) gives th...
Figure 4-22. (a) Storing the free list on a linked list. (b) A bitmap.
Keeping Track of Free Blocks (1)
Tanenbaum, Modern ...
Figure 4-23. (a) An almost-full block of pointers to free disk blocks
in memory and three blocks of pointers on disk. (b) ...
Figure 4-24. Quotas are kept
track of on a per-user basis
in a quota table.
Disk Quotas
Tanenbaum, Modern Operating System...
Backups to tape are generally made to
handle one of two potential problems:
1. Recover from disaster.
2. Recover from stup...
Figure 4-25. A file system to be dumped. Squares are directories,
circles are files. Shaded items have been modified since...
Figure 4-26. Bitmaps used by the logical dumping algorithm.
File System Backups (3)
Tanenbaum, Modern Operating Systems 3 ...
Figure 4-27. File system states. (a) Consistent. (b) Missing block.
(c) Duplicate block in free list. (d) Duplicate data b...
Figure 4-28. The buffer cache data structures.
Caching (1)
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall...
• Some blocks, such as i-node blocks, are rarely
referenced two times within a short interval.
• Consider a modified LRU s...
Figure 4-29. (a) I-nodes placed at the start of the disk.
(b) Disk divided into cylinder groups, each with its own blocks
...
Figure 4-30. The ISO 9660 directory entry.
The ISO 9660 File System
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Pren...
Rock Ridge extension fields:
1. PX - POSIX attributes.
2. PN - Major and minor device numbers.
3. SL - Symbolic link.
4. N...
Joliet extension fields:
1. Long file names.
2. Unicode character set.
3. Directory nesting deeper than eight levels.
4. D...
Figure 4-31. The MS-DOS directory entry.
The MS-DOS File System (1)
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Pren...
Figure 4-32. Maximum partition size for different block sizes. The
empty boxes represent forbidden combinations.
The MS-DO...
Figure 4-33. A UNIX V7 directory entry.
The UNIX V7 File System (1)
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Pren...
Figure 4-34. A UNIX i-node.
The UNIX V7 File
System (2)
Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, I...
Figure 4-35. The steps in looking up /usr/ast/mbox.
The UNIX V7 File System (3)
Tanenbaum, Modern Operating Systems 3 e, (...
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  1. 1. MODERN OPERATING SYSTEMS Third Edition ANDREW S. TANENBAUM Lecture 24: Chapter 4 File Systems Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  2. 2. Administration Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639 • Homework and MP2 grades available • MP3 available •http://www.cs.uiuc.edu/class/sp08/cs423/MPs/M •Spring Break – keep up with mps and reading. Read T: Chapter 4 and ULK: Chapter 12, 14, 15, 27 (VFS, Disk Caches, Accessing Regular Files, EXT2 File System)
  3. 3. Figure 4-18. Position of the virtual file system. Virtual File Systems (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  4. 4. Figure 4-19. A simplified view of the data structures and code used by the VFS and concrete file system to do a read. Virtual File Systems (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  5. 5. Figure 4-20. Percentage of files smaller than a given size (in bytes). Disk Space Management Block Size (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  6. 6. Figure 4-20. Percentage of files smaller than a given size (in bytes). Disk Space Management Block Size (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  7. 7. Figure 4-21. The solid curve (left-hand scale) gives the data rate of a disk. The dashed curve (right-hand scale) gives the disk space efficiency. All files are 4 KB. Disk Space Management Block Size (3) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  8. 8. Figure 4-22. (a) Storing the free list on a linked list. (b) A bitmap. Keeping Track of Free Blocks (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  9. 9. Figure 4-23. (a) An almost-full block of pointers to free disk blocks in memory and three blocks of pointers on disk. (b) Result of freeing a three-block file. (c) An alternative strategy for handling the three free blocks. The shaded entries represent pointers to free disk blocks. Keeping Track of Free Blocks (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  10. 10. Figure 4-24. Quotas are kept track of on a per-user basis in a quota table. Disk Quotas Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  11. 11. Backups to tape are generally made to handle one of two potential problems: 1. Recover from disaster. 2. Recover from stupidity. File System Backups (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  12. 12. Figure 4-25. A file system to be dumped. Squares are directories, circles are files. Shaded items have been modified since last dump. Each directory and file is labeled by its i-node number. File System Backups (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  13. 13. Figure 4-26. Bitmaps used by the logical dumping algorithm. File System Backups (3) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  14. 14. Figure 4-27. File system states. (a) Consistent. (b) Missing block. (c) Duplicate block in free list. (d) Duplicate data block. File System Consistency Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  15. 15. Figure 4-28. The buffer cache data structures. Caching (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  16. 16. • Some blocks, such as i-node blocks, are rarely referenced two times within a short interval. • Consider a modified LRU scheme, taking two factors into account: 1. Is the block likely to be needed again soon? 2. Is the block essential to the consistency of the file system? Caching (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  17. 17. Figure 4-29. (a) I-nodes placed at the start of the disk. (b) Disk divided into cylinder groups, each with its own blocks and i-nodes. Reducing Disk Arm Motion Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  18. 18. Figure 4-30. The ISO 9660 directory entry. The ISO 9660 File System Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  19. 19. Rock Ridge extension fields: 1. PX - POSIX attributes. 2. PN - Major and minor device numbers. 3. SL - Symbolic link. 4. NM - Alternative name. 5. CL - Child location. 6. PL - Parent location. 7. RE - Relocation. 8. TF - Time stamps. Rock Ridge Extensions Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  20. 20. Joliet extension fields: 1. Long file names. 2. Unicode character set. 3. Directory nesting deeper than eight levels. 4. Directory names with extensions Joliet Extensions Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  21. 21. Figure 4-31. The MS-DOS directory entry. The MS-DOS File System (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  22. 22. Figure 4-32. Maximum partition size for different block sizes. The empty boxes represent forbidden combinations. The MS-DOS File System (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  23. 23. Figure 4-33. A UNIX V7 directory entry. The UNIX V7 File System (1) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  24. 24. Figure 4-34. A UNIX i-node. The UNIX V7 File System (2) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
  25. 25. Figure 4-35. The steps in looking up /usr/ast/mbox. The UNIX V7 File System (3) Tanenbaum, Modern Operating Systems 3 e, (c) 2008 Prentice-Hall, Inc. All rights reserved. 0-13-6006639
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