A useful posting explaining why Linux does not need defragmenting.

Posted: March 18, 2014. At: 10:43 PM. This was 4 years ago. Post ID: 7049
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If you are interested in how the Linux filesystem works, then this is a posting you really need to read: http://geekblog.oneandoneis2.org/index.php/2006/08/17/why_doesn_t_linux_need_defragmenting. This is a posting explaining how the Linux filesystem stores file and why it does not need to defragment the filesystem as it stores files more efficiently. I have never wanted to defragment a Linux filesystem and I have used quite a lot of Linux distributions. The filesystem stores files more efficiently than a FAT or NTFS filesystem does. There is an answer in AskUbuntu that gives some insight into how you can defragment a Linux filesystem, but this is not something that you really need to do. Linux filesystems, being more efficient are more reliable as a consequence and do not need as much attention as a Windows filesystem would. Although you do not need to defrag as much as you used to with Windows `98, and you do not get the cool window with the blocks moving around like you did in the olden days of Windows. That would make a cool screensaver though. There is more information here about the defragmentation of Linux filesystems and how this is handled by Linux transparently. The key seems to be maintaining a certain amount of free space on your Linux partition to allow the files to move around.

The default free space recommendation for ext4 is 5%, if you have at least this amount of space, your partition will not get fragmented. But with the size of modern hard disks reaching 3 terabytes, this should not be too difficult. You may run the below command to assess the level of fragmentation on your hard drive.

[email protected]:~$ sudo e4defrag -c /dev/sda5
<Fragmented files>                             now/best       size/ext
1. /var/log/pm-powersave.log.1                  20/1              4 KB
2. /home/homer/.cache/chromium/Default/Media Cache/index
7/1              4 KB
3. /var/log/pm-powersave.log                    25/1              4 KB
4. /var/lib/lightdm/.cache/upstart/indicator-datetime.log
6/1              4 KB
5. /var/log/wtmp                                45/1              4 KB
Total/best extents                205081/204017
Average size per extent            85 KB
Fragmentation score                0
[0-30 no problem: 31-55 a little bit fragmented: 56- needs defrag]
This device (/dev/sda5) does not need defragmentation.

Then you may run this command to defragment your hard drive.

[email protected]:~$ sudo e4defrag /dev/sda5

This does work very well, but you will not need to run this often.

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