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Re: Is FSFS compressing stored data?

From: Mark Phippard <MarkP_at_softlanding.com>
Date: 2004-10-14 18:54:40 CEST

Greg Hudson <ghudson@MIT.EDU> wrote on 10/14/2004 11:55:21 AM:

> > I believe Greg's point is that the presence of these full-texts,
> > especially if you have a lot of branches, accounts for a lot of the
> > difference in the repository sizes. Also, if I understand Greg, even
the
> > head revision in fsfs undergoes some degree of compression, such as
> > stripping out whitespace etc...
>
> Stripping out whitespace? No.
>
> In FSFS, the first rev of a file is stored as a delta against empty,
> which is a form of compression comparable to gzip (though not quite as
> good). Later revs of the file are stored as deltas against earlier
> revs--but not always the most immediate earlier rev. See
> http://svn.collab.net/repos/svn/trunk/notes/skip-deltas for details.

To us mortals, a delta against empty would imply the same end result as a
full text. I know you didn't mean that, so I was suggesting that there is
some degree of compression even in that scenario.

What I meant by stripping out whitespace, is that if I had 100 consecutive
spaces the algorithm would probably compress that down to something far
less than 100 bytes. I have no idea what the delta algorithm, or gzip,
actually does, I just thought that might be something that us lay persons
might understand.

Thanks

Mark

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Received on Thu Oct 14 18:55:34 2004

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