[gentoo-user] Re: Fragmentation of my drives. Curious mostly

[Nikos Chantziaras]

Dale wrote:
> Nikos Chantziaras wrote:
>> OK, I once again verified that fragmentation seems to be a big issue
>> even on Linux.  I just migrated to ext4, and in order to do that I had
>> to rsync, format and rsync back.  The result is similar to the last
>> time I did this (over 8 months ago):
>>
>> emerge --sync takes 15 seconds (at least 3 minutes yesterday)
>> update-eix takes 2 seconds (20 seconds yesterday)
>>
>> And I don't believe it's due to ext4.  It's a nice speed-up from ext3,
>> but not THAT nice.
>
> Well, try as I may, I could not get mine past 10% on resiserfs.
> Fragmentation happens on any file system but I think the point is that
> Linux doesn't get as bad as the windoze file system.  10% or so is not
> to bad depending on the size of the files.  Files that are large will
> have to be fragmented no matter what file system you use.
>
> I posted in another the reply right after a copy to another drive.  I
> think that was before I even booted into the OS and was still on the
> CD.  It is around 2% or so.  I doubt given that condition that it could
> get any better.

I think the main problem may not be so much fragmentation of files, but 
rather their position on disk.  Even if files are not fragmented, if 
they are located too far from each other even though they're related 
(same directory for example) or there's simply too much empty space 
between files (I think this is intentional in order to reduce 
fragmentation) then seek times get really bad.  After I rsync the data 
back, it's nicely and sequentially laid out on disk.  I guess over time 
it starts to get further apart again (to combat fragmentation) and 
emerge --sync goes up from 15 seconds to 2 minutes again.  Even though 
the files aren't fragmented at all.

Some defrag apps for Windoze actually offer to put the files back closer 
together without trying to defragment at all.  I guess this is why :P