Disk defragmenter in Linux

[Mike McCarty]

Jim Cornette wrote:
> John Summerfied wrote:
> 
>> Jeff Vian wrote:
>>
>>>
>>> Exactly, and IIRC the filesystem knows that if it needs X amount of
>>> space for a file, then Y number of inodes are marked for use for that
>>> file at the beginning.  Thus space allocated is as contiguous as is
>>> efficient for read/write on the disk.
>>
>>
>>
>> If "the filesystem knows that if it needs X amount of space for a 
>> file," that implies there's a way of telling it that.
>>
>> How's that done? I don't recall any system call for *x (there is one 
>> for OS/2), and one could do it in JCL in IBM's OS in the 60s), but in 
>> the *x world I've never seen a way to do it.
> 
> 
> 
> 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.

On my system I did this...

# filefrag /usr/bin/* | sort -k2 -nr | grep 'would be'

Here're the first few entries...

/usr/bin/emacs: 248 extents found, perfection would be 1 extent
/usr/bin/emacs-21.3: 248 extents found, perfection would be 1 extent
/usr/bin/kermit: 80 extents found, perfection would be 1 extent
/usr/bin/kbabel: 45 extents found, perfection would be 1 extent
/usr/bin/ddd: 45 extents found, perfection would be 1 extent
/usr/bin/gthumb: 41 extents found, perfection would be 1 extent
/usr/bin/gdbtui: 36 extents found, perfection would be 1 extent
/usr/bin/elinks: 30 extents found, perfection would be 1 extent
/usr/bin/iniomega: 22 extents found, perfection would be 1 extent
/usr/bin/kpersonalizer: 21 extents found, perfection would be 1 extent
/usr/bin/artsd: 21 extents found, perfection would be 1 extent
/usr/bin/artscat: 20 extents found, perfection would be 1 extent
/usr/bin/kiconedit: 19 extents found, perfection would be 1 extent
/usr/bin/glade-2: 19 extents found, perfection would be 1 extent
/usr/bin/karm: 18 extents found, perfection would be 1 extent
/usr/bin/dia: 18 extents found, perfection would be 1 extent
/usr/bin/designer3: 18 extents found, perfection would be 1 extent
/usr/bin/designer: 18 extents found, perfection would be 1 extent
/usr/bin/kppplogview: 16 extents found, perfection would be 1 extent
/usr/bin/kfontinst: 16 extents found, perfection would be 1 extent
/usr/bin/civclient-xaw: 15 extents found, perfection would be 1 extent
/usr/bin/cdrecord: 15 extents found, perfection would be 1 extent
/usr/bin/knewstickerstub: 14 extents found, perfection would be 1 ext

Surely those who argue that ext3 does not get fragmented
during install don't think that 248 extents is "not
significant fragmentation".

I assure you that I have done nothing on my system to try to
fragment emacs.

Mike
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