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Re: CVSNT and Subversion binary file handling comparison

From: Phillip Susi <psusi_at_cfl.rr.com>
Date: 2006-03-19 22:14:55 CET

The --rsyncable option to gzip results in some loss of compression
because it stops and restarts the compressor periodically to contain the
fallout from small changes in the source data. To my knowledge nobody
has tried to do this with bzip2 because the loss in compression would be
even higher with that compressor.

In any case, IIRC, "zip" files individually compress each file packed
inside them rather than compressing the entire archive as a solid chunk.
  This results in adding or removing files leaving small binary diffs
with the older version.

Ryan Schmidt wrote:
> Alfredo, Subversion works best with text files and other files
> (generally uncompressed files) where the difference between one revision
> of a file and the next can be efficiently expressed as a diff. Try your
> test again with uncompressed files and see if Subversion performs any
> better in regard to this metric. Also, note that some compression
> formats, like gzip, offer an option that makes them work better for
> programs that want to compute differences; gzip calls this the
> "rsyncable" option because it's commonly used with the rsync program. I
> found this page which describes that option:
> http://glasnost.beeznest.org/articles/206
> If you can compress your files with gzip and the rsyncable option
> instead of zip, you may see better disk space usage in the repository.
> bzip2 compresses better than gzip; Google may be able to help you
> discover whether bzip2 offers a similar "rsyncable" option.

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Received on Sun Mar 19 22:15:55 2006

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