On 09/11/2012 07:45 PM, David Sterba wrote: > On Tue, Sep 11, 2012 at 07:12:58PM +0800, ching wrote: >>> 1. According to btrfs wiki, defragment a COW file will produce two >>> unrelated files. >>> >>> Does it apply to the "autodefrag" mount option? >> can anybody helps on question 1? > The data blocks associated with the files (that were originally created > by snapshotting and thus shared the same blocks) will become unshared, > so yes it would appear like two unlreated files. > > Autodefrag option affects only newly written data. With current > implementation it could unshare some extents if the defragged range > picked by autodefrag logic overlaps with an existing one. > > >From my experience, running 'btrfs fi defrag' with autodefrag on > produced better result. Beware that there are some unfixed deadlocks > that may happen with autodefrag enabled. > > david >
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