How inodes Work
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One of the tutorials I gave at University of Wollongong on inodes. Describes direct, single, double and triple linking, and how that all ties together with addressable space.
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How inodes Work
- 1. inodes explained Tutorial 3 - CSCI212 by: Roman Tarnavski
- 2. Data Blocks A file system contains ‘blocks’ which hold data called inodes. A inode describes a single file in the file system. Typical information described includes, ownership, modification times, size and permissions. We call this information meta-data. Source: CSCI212 Lecture Notes by: Daniel Saffioti
- 3. Data Blocks Data Blocks The remainder of the file system (larger proportion) contains data blocks. These store the contents of files. Source: CSCI212 Lecture Notes by: Daniel Saffioti
- 4. Source: CSCI212 Lecture Notes by: Daniel Saffioti
- 5. Your typical inode Mode Permissions Size Timestamps Direct Blocks Single Double Triple
- 6. Direct Data Block 1 Data Block 2 . . . Direct Direct Data Block 3 Direct Direct Direct Direct Direct Direct Direct Direct Direct Direct Single Double Triple
- 7. Single Direct Data Block 1 Direct Data Block 2 Direct Direct Direct Data Block 2048 Direct Address 1 Direct Address 2 Direct . Direct . . Direct Address 2048 Direct Direct Single Double Triple
- 8. Double Data Block 1 Direct Data Block 2 Direct Direct Direct Address 1 Data Block 2048 Direct Address 2 Direct . . . Direct Address 1 Direct Address 2 Address 2048 Direct . Data Block 1 . . Direct Data Block 2 Direct Address 2048 Direct Address 1 Single Data Block 2048 Address 2 Double . . Triple . Address 2048
- 9. Triple Data Block 1 Data Block 2 Direct Address 1 Direct Data Block 2048 Address 2 Direct . Direct . . Address 1 Address 1 Direct Address 2 Address 2 Address 2048 Direct . . Data Block 1 Direct . . . . Data Block 2 Direct Address 2048 Address 2048 Direct Direct Address 1 Data Block 2048 Direct Address 2 . Direct . . Single Address 1 Double Address 2048 Address 2 Triple . . Data Block 1 . Data Block 2 Address 2048 Address 1 Data Block 2048 Address 2 . . Address 1 . Address 2 Address 2048 . . . Address 2048
- 10. All Together?
- 11. Data Block 1 Data Block 2 . . . Direct Data Block 1 Direct Data Block 3 Data Block 2 Direct Direct Direct Data Block 2048 Data Block 1 Direct Address 1 Data Block 2 Direct Address 1 Address 2 Direct Data Block 2048 Address 2 . Direct . . . Direct . . Address 2048 Data Block 1 Direct Address 2048 Data Block 2 Direct Single Double Address 1 Data Block 2048 Triple Address 2 Address 1 . Data Block 1 . Address 2 . Data Block 2 . . Address 2048 . Address 1 Address 2048 Data Block 2048 Address 2 . . . Address 1 Address 1 Address 2 Address 2 Address 2048 . . Data Block 1 . . . . Data Block 2 Address 2048 Address 2048 Address 1 Data Block 2048 Address 2 . . . Address 1 Address 2048 Address 2 . . Data Block 1 . Data Block 2 Address 2048 Address 1 Data Block 2048 Address 2 . . Address 1 . Address 2 Address 2048 . . . Address 2048
- 12. Maximum Size of Direct Blocks
- 13. Maximum Size of Direct Blocks Where did the 2048 Addresses come from?
- 14. Maximum Size of Direct Blocks Where did the 2048 Addresses come from? Assuming 32-bit architectures
- 15. Maximum Size of Direct Blocks Where did the 2048 Addresses come from? Assuming 32-bit architectures 32-bit = 4 bytes (32 / 8)
- 16. Maximum Size of Direct Blocks Where did the 2048 Addresses come from? Assuming 32-bit architectures 32-bit = 4 bytes (32 / 8) Thus 8192 /4 [block size] [bytes per addressable block]
- 17. Maximum Size of Direct Blocks Where did the 2048 Addresses come from? Assuming 32-bit architectures 32-bit = 4 bytes (32 / 8) Thus 8192 /4 [block size] [bytes per addressable block] = 2048 Addressable Blocks
- 18. Questions What is the maximum possible file size that can be represented via direct data blocks?
- 19. Maximum Size of Direct Blocks block size blocks = 8192 x 12 = 98,304 bytes = 96Kb
- 20. Maximum FileSize using First-Indirect Linking
- 21. Maximum FileSize using First-Indirect Linking Direct: 12 blocks @ 8192 bytes (12 x 8192)
- 22. Maximum FileSize using First-Indirect Linking Direct: 12 blocks @ 8192 bytes (12 x 8192) =96Kb
- 23. Maximum FileSize using First-Indirect Linking Direct: 12 blocks @ 8192 bytes (12 x 8192) =96Kb Indirect: 2048 @ 8192 (2048 x 8192) = 16,384 Kb = 16,480 [Inclusive of Direct] = 16.09Mb
- 24. Maximum using Double Indirect 16,875,520 x 2048 addressable blocks = 34,561,064,960 bytes = 32,960 Mbytes
- 25. Maximum Filesize [direct + single + double + triple] 2048 x 32.1875Gb = 64.375 Tb
- 26. Overhead
- 27. Overhead Wish to store: 8,437,760 bytes
- 28. Overhead Wish to store: 8,437,760 bytes 8437760 / 8192 [bytes per block] = 1030 blocks x 4 bytes [per address] BUT
- 29. Overhead Wish to store: 8,437,760 bytes 8437760 / 8192 [bytes per block] = 1030 blocks x 4 bytes [per address] BUT 12 Blocks are stored directly
- 30. Overhead Wish to store: 8,437,760 bytes 8437760 / 8192 [bytes per block] = 1030 blocks x 4 bytes [per address] BUT 12 Blocks are stored directly Hence we only have 1018 blocks
- 31. Overhead Wish to store: 8,437,760 bytes 8437760 / 8192 [bytes per block] = 1030 blocks x 4 bytes [per address] BUT 12 Blocks are stored directly Hence we only have 1018 blocks 1018 x 4 bytes = 4072 bytes = 3.98Kbytes