1. CSE 451: Operating Systems Autumn 2009 Module 18 File System Summary
Ed Lazowska
Allen Center 570 1

2. © 2009 Gribble, Lazowska, Levy, Zahorjan
UFS
Hardware Device
inodes
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data blocks
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4/14/2019
© 2009 Gribble, Lazowska, Levy, Zahorjan

3. © 2009 Gribble, Lazowska, Levy, Zahorjan
FFS
Low throughput addressed by:
larger blocks
cylinder groups
aggressive caching
hardware awareness
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4/14/2019
© 2009 Gribble, Lazowska, Levy, Zahorjan

4. JFS Example: file creation Main memory cache Journal App + requests
Long post-crash boot times addressed by:
transactional journal of changes
propagated back to “real” file system asynchronously
Example: file creation …
Start t
Alloc inode 1067
Write inode 1067 w/ [data]
Write block w/ [data]
Commit t ….
Main memory cache
Journal +
some file system
App
requests
If data block updates are not journaled, after a crash files may have garbage blocks
4/14/2019
© 2009 Gribble, Lazowska, Levy, Zahorjan

5. © 2009 Gribble, Lazowska, Levy, Zahorjan
Write throughput addressed by:
the file system is a log
LFS
Main memory cache
file 2
file1
Segments
file1
inode maps
4/14/2019
© 2009 Gribble, Lazowska, Levy, Zahorjan