Disk defragmenter in Linux

Jim Cornette fc-cornette at insight.rr.com
Sat Dec 31 02:15:38 UTC 2005


John Summerfied wrote:
> > Since the discussions regarding fragmentation on ext3 filesystems
> > was pretty long running. I decided to try filefrag /usr/bin/* |sort
> > |grep 'would be' and the output showed a lot of fragmentation. One
> > of the files was up to 45. /usr/bin/postgres: 45 extents found,
> > perfection would be 1 extent I outputted the findings to a file
> > which ended up being around 75 kb The log files didn't seems to be
> > as fragmented as I expected. Another pecularity was that some of
> > the files did not seem to be things that I use much. Another
> > excerpt from the query. /usr/bin/php: 52 extents found, perfection
> > would be 1 extent /usr/bin/php-cgi: 62 extents found, perfection
> > would be 1 extent
> >
> > My system is running development. This of course means frequently
> > updated programs. Checking usr/lib showed fragmentation also.
> > /usr/lib/libXm.so.4: 48 extents found, perfection would be 1 extent
> > /usr/lib/libXm.so.4.0.0: 48 extents found, perfection would be 1
> > extent .. /usr/lib/libxvidcore.so.4: 49 extents found, perfection
> > would be 1 extent
> >
> > I guess fragmentation is present on the system and probably needs
> > addressed or a less fragmented filesystem type needs implemented.
>
>  extent ^= fragmentation. On filesystems I know, extents can be on
>  consecutive areas (sectors, blocks, tracks) of disk. You need better
>  info than that to see whether you have a fragmentation problem.
>  filefrag will give it to you, but it needs a wrapper to make sense to
>  Mere Mortals.
>
Thanks, I did not take into account the possibility the file would be in 
series and read in order. Fragmentation is not of major importance to me 
at present. Thanks for pointing out the additional factors that need 
consideration.

>  fwiw summer at bilby ~]$ sudo filefrag /usr/sbin/postfix
>  /usr/X11R6/lib/libXm* /usr/sbin/postfix: 1 extent found
>  /usr/X11R6/lib/libXm.a: 1 extent found /usr/X11R6/lib/libXm.so: 1
>  extent found /usr/X11R6/lib/libXm.so.2: 1 extent found
>  /usr/X11R6/lib/libXm.so.2.1: 1 extent found
>  /usr/X11R6/lib/libXm.so.3: 1 extent found
>  /usr/X11R6/lib/libXm.so.3.0.2: 1 extent found
>  /usr/X11R6/lib/libXmu.a: 1 extent found /usr/X11R6/lib/libXmu.so: 2
>  extents found, perfection would be 1 extent
>  /usr/X11R6/lib/libXmu.so.6: 2 extents found, perfection would be 1
>  extent /usr/X11R6/lib/libXmu.so.6.2: 2 extents found, perfection
>  would be 1 extent /usr/X11R6/lib/libXmuu.a: 1 extent found
>  /usr/X11R6/lib/libXmuu.so: 1 extent found
>  /usr/X11R6/lib/libXmuu.so.1: 1 extent found
>  /usr/X11R6/lib/libXmuu.so.1.0: 1 extent found
>
>  This system was installed as Fedora Core 3, and all these package
>  subsequently replaced (with force where necessary) with packages I
>  built myself from RHEL 4 source. That is, they have all been updated
>  after installation.

Thanks for the comparison. The fact that you brought your system up from 
FC3 to RHEL home brewed edition is interesting also.

>
>  Checking lib and bin directories under /usr, I see no more than three
>  extents.
>
>  I note my file placement's different from yours.

Running rawhide vs.  RHEL 4 might be the difference in comparison.
Jim




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