In general ext3 filesystems have very low fragmentation, so you don't need to defragment. This is because the kernel places files on the hard drive intelligently, reducing any fragmentation. Ext3 fragmentations is generally less than 10%. But if you use and ext3 filesystem to store large files, add and deleting them, on a mostly full partition, fragmentations can become very high. Greater than 50%. This is how to you can defragment a partitions.

Tools[]

Shake - http://www.vleu.net/shake/

Checking Fragmentation[]

Display partition's fragmentation percentage[]

unmout the partition
Execute: fsck -nvf /dev/sdb2

Example output of a partition with 79.5% fragmentation:

fsck from util-linux-ng 2.16
e2fsck 1.41.9 (22-Aug-2009)
Pass 1: Checking inodes, blocks, and sizes
Pass 2: Checking directory structure
Pass 3: Checking directory connectivity
Pass 4: Checking reference counts
Pass 5: Checking group summary information

1955 inodes used (0.08%)
    1554 non-contiguous files (79.5%)
0 non-contiguous directories (0.0%)
# of inodes with ind/dind/tind blocks: 1660/1224/0
3706004 blocks used (72.40%)
0 bad blocks
1 large file

1825 regular files
121 directories
0 character device files
0 block device files
0 fifos
0 links
0 symbolic links (0 fast symbolic links)
0 sockets
--------
1946 files

Display files that are fragmented[]

Execute: shake -pvv /mnt/ext3_partition/ | awk '{ printf("%06d,%s\n", $4, $8) }' | sort > fragmented_file_list.txt
Wait a long time, for it to complete
When done, view fragmented_file_list.txt

Example output:
- First column is # of fragments
- Second column is the file that is fragmented

000001,/mnt/ext3_partition/file1.avi
000002,/mnt/ext3_partition/file2.avi
004597,/mnt/ext3_partition/file3.avi

Defragmenting[]

Install shake
Make sure the partition is mounted with the "user_xattr" option
- To check execute: mount
  - Example output: /dev/sdb2 on /mnt/ext3_partition type ext3 (rw,noatime,user_xattr)
- If you don't have that option add it to /etc/fstab
  - Example: /dev/sdb2 /mnt/ext3_partition ext3 auto,noatime,user_xattr 0 0
Run shake to defragment
- Execute: shake --old=0 --bigsize=0 /mnt/ext3_partition
Wait a long time for the process to finish

Optimizing the defragmentation[]

Make as much free space as possible.
- You wont be able to do a good defragmentation without empty space to move blocks. 15% or greater is recommended.
Keep a log of fragmentation, before and after, to show the improvements
- Execute before: shake -pvv /mnt/ext3_partition/ | awk '{ printf("%06d,%s\n", $4, $8) }' | sort > fragmented_file_list-before.txt
- Execute after: shake -pvv /mnt/ext3_partition/ | awk '{ printf("%06d,%s\n", $4, $8) }' | sort > fragmented_file_list-after.txt
- And compare
Running shake multiple times, can remove more fragmentation

How to defragment an ext3 filesystem

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