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    SubjectRe: very poor ext3 write performance on big filesystems?
    On Mon, Feb 18, 2008 at 09:16:41AM -0500, Theodore Tso wrote:
    > ext3 tries to keep inodes in the same block group as their containing
    > directory. If you have lots of hard links, obviously it can't really
    > do that, especially since we don't have a good way at mkdir time to
    > tell the filesystem, "Psst! This is going to be a hard link clone of
    > that directory over there, put it in the same block group".

    Hmm, you think such a hint interface would be worth it?

    >
    > > What has helped a bit was to recreate the file system with -O^dir_index
    > > dir_index seems to cause more seeks.
    >
    > Part of it may have simply been recreating the filesystem, not

    Undoubtedly.

    > necessarily removing the dir_index feature. Dir_index speeds up
    > individual lookups, but it slows down workloads that do a readdir

    But only for large directories right? For kernel source like
    directory sizes it seems to be a general loss.

    -Andi



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