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From Jon Stafford <Jon.Staff...@complyserve.com>
Subject not storing diffs of binary files
Date Mon, 08 Aug 2011 16:49:45 GMT
I'm trying to understand why subversion isn't just storing diffs of some binary files.  It
looks like it's taking up more space than it needs to.

At length the issue is described here: http://stackoverflow.com/q/6917505/277208

The more summarized version is...

I understand that subversion stores files differentially (compressed), even for binary files.
 And subversion uses Xdelta to help with this.

I can do a standalone xdelta on my 50MB zip files:
xdelta3.0z.x86-64.exe -e -s v1_path\data.zip v2_path\data.zip v1v2_delta.file

and get a nicely small v1v2_delta.file which is about 3MB.

But when I check successive versions of the data.zip into a subversion repository (FSFS, version
1.6.11) I get two ~50MB files in db\revs\0

I appreciate minimizing disk usage isn't the only thing, e.g. performance may be more important.
 Being able to configure this would be useful in my situation.

I've spent a long time trying to figure out what is going on and not got very far.  I guess
this behaviour is probably deliberate - it would be really interesting to have an idea of
different factors deciding subversion behaving in this way.

Thanks
Jon

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