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On Sat, Nov 26, 2011 at 7:14 PM, Rich Freeman <rich0@g.o> wrote: |
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> isn't supported. It is available in stable coreutils. Some speculate |
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> that this option could increase fragmentation (both copies will share |
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> extents from the original file, and have some extents of their own), |
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> but btrfs doesn't overwrite anything in-place so fragmentation is a |
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> potential issue with any file modification (change one byte in the |
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Adding to your comments on this: |
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To mitigate such issues, newer versions of the btrfs fs driver have |
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automatic online defragmentation as well. Works quite well for |
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moderate fragmentation. |
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A particularly ghastly example where fragmentation issues become |
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pathological in nature are files that are fsync()ed very frequently. A |
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typical example are the *.sqlite files in ~/.mozilla which easily get |
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hundreds or even thousands of fragments after a few hours worth of |
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firefox usage (can be verified with filefrag). |
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To fix such things, regular online defragmentation of those specific |
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files can be done using `btrfs fi defrag <file>`. |
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-- |
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~Nirbheek Chauhan |
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Gentoo GNOME+Mozilla Team |
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