1. 9 Advanced Operating Systems File System Internals

2. 10 UNIX File System Organisation The Traditional UNIX organisation from Ed 7 onwards has been –Boot Block, Super Block, Inodes, Data

3. 11 UNIX File System Organisation Searching and allocation is done through logical device and inumber

4. 12 UNIX File System Organisation Problems of Traditional UNIX FS –Fragmentation of disc –No way to use disc geometry –Short file names

5. 13 Berkeley Fast File System Restructured File System organisation using cylinder groups –1 or more cylinders per group –Identical superblocks in cylinder group –Superblocks offset for each in cylinder group

6. 14 Berkeley Fast File System Inode/file allocation –File inode is allocated in parent directory cylinder group –New directory placed in new cylinder group –Large and small files are segregated –Use of 8k byte blocks & 1k fragements

7. 15 Berkeley Fast File System Filename size changes –255 character file names Changed directory organisation –Quota system introduced –Symbolic links introduced –File truncation introduced

8. 16 Linux file system Added VFS – Virtual File System –Allows other system to be added –Clean, object orientated, design of system 3 parts –Inode object –File object –File system object

9. 17 Virtual File System

10. 18 Virtual File System VFS Objects define an action for each file system Each object has a pointer into a table of functions for each file system implementation File system object is the hierarchy Files found through fs-inode paring