Newbie Info
John Wendel
john.wendel at metnet.navy.mil
Fri Oct 19 22:17:04 UTC 2007
aragonx at dcsnow.com 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
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