Re: Does defragmenting even work

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On Thu, 2013-02-28 at 15:35 +0100, Swâmi Petaramesh wrote:
> BTW...
> 
> I'm not even sure that "btrfs filesystem defrag <somefile>" actually
> does anything...
> 
> If I run "filefrag <somefile>" afterwards, it typically shows the same
> number of fragments that it did prior to running defrag...

If you have compression enabled in your system, the files are split up
into smallish extents for the compression blocks. Merely counting the
number of fragments doesn't really give you any useful information - you
have to check if the fragments are contiguous.

Try running "filefrag -v somefile", and compare the 'physical' and
'expected' values to look for gaps between fragments.

-- 
Calvin Walton <calvin.walton@xxxxxxxxxx>

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