On Thu, Feb 28, 2013 at 03:35:28PM +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... > > I'm not sure about how it actually works and what I should expect... If you have a compressed file, each compression block (128k of compressed data, if I remember rightly) will show up as a separate fragment, even if it's contiguous with the others -- it's an artefact of the way that fiemap/filefrag calculates fragments, and the way that btrfs reports compressed files. Also, on a full filesystem, complete defragmentation may not be completely possible. Similarly, very large files may not be easy or possible to defragment fully -- a 2GB file with four fragments isn't exactly a problem, for example. Hugo. -- === Hugo Mills: hugo@... carfax.org.uk | darksatanic.net | lug.org.uk === PGP key: 515C238D from wwwkeys.eu.pgp.net or http://www.carfax.org.uk --- I'm all for giving people enough rope to shoot themselves in --- the foot -- Andreas Dilger
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