aragonx@xxxxxxxxxx wrote:
As you can gather from the other responses. defrag isn't used often on a
Linux system. It isn't needed; the Linux kernel and friends do much
better job of allocating space on a hard disk.
The following two sites begin the explanation. You can explore more
from there.
http://en.wikipedia.org/wiki/Defragmentation#_note-4
http://pl.atyp.us/wordpress/?p=241
I have had several threads on this very list about this subject. The
threads went something like this (dramatization):
Me: I want to defrag my disk
Everyone else: Shut up noob. Linux doesn't need to do that winblows M$
nonsense.
Me: How could a filesystem never get fragmented. It's not possible.
Everyone else: Go back to M$ you. We will have none of this Linux bashing.
Fast forward to today, a few years later. I've got several file systems
that are showing 20 - 30% non-contiguous as reported by fsck and I have no
way other than a cp or dump to fix it. This just doesn't seem right.
The real question is not so much if there is fragmentation or not. It is,
is there a performance difference or not. Honestly, I can't say for sure.
I don't have reliable tests from years ago as to how long it took to
copy, write or read from a file to compare it to. I can say this, my
performance is not bad enough to warrant the file system dump and restore.
So, in conclusion, after years of heavy usage, my file systems still
perform reasonably well. It would be nice to be able to defragment your
hard drive but realistically, it isn't much needed.
I hope that answers your question with real world experience.
---
Will Y.
We haven't yet reached filesystem perfection!
A quick google for "ext4" reveals that the file system gods think that
it is worth the effort of writing a new (and incompatible with
ext3) filesystem. The development version of the code is in the
current kernel.org kernel (and in F8 ???). Among its features are a
new block allocation scheme that keeps files contiguous and "online
defragmentation" (whatever that is). I assume that in a few years
we'll be complaining that the online defrag demon is taking too much
CPU time on our 64 core box.
I amused that there is an entire industry devoted to selling software
to defrag winblows filesystems.
Regards,
John
