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Re: application ill-suited for svn?

From: Matt Doran <matt.doran_at_papercut.biz>
Date: 2006-01-29 01:21:49 CET

Hi Dan,

Even though Subversion has global revision numbers, it only stores the
diffs of files that have changed in the commit (plus any meta-data that
goes along with the commit ... like commit messages, etc). With FSFS
things are slightly more complex than that, it uses a clever technique
called skip-deltas to optimize accessing recent revisions, without
having to have write permissions to previous revisions when
committing. However, there is a slight size penalty with this
approach. You can read about this here:
http://svn.collab.net/repos/svn/trunk/notes/skip-deltas. My
understanding is that because of this, repositories using the BDB
backend will be a little smaller than FSFS, but BDB has some other

I'm surprised that each commit is adding 700K. It doesn't sound right,
but an svn dev might be able to add more to the discussion. In my
experience SVN is more space efficient than CVS.

Is there a possibility that you committing more than you think in each
commit? i.e. if you run "svn log -v" on recent revisions ... are
more changed files listed than you would expect?


Dan White wrote:
> Sorry, I was wrong about the number of files. We actually have about
> 13k files. Each commit now is adding almost 700k to /dv/revs. If we
> were versioning only at the file level (which is all we really require),
> each commit should only use at most the size of the files being updated,
> plus any commit comments. This is one reason I'd consider going back to
> cvs for this particular repository. I believe we'd have to do a
> significant amount of work to recode our app to interface with cvs.
> As far as pruning older revisions goes, that's possible for roughly 25%
> of the files in the repository. I rebuilt the repository with the
> historical revisions for the other 75%, then imported only the most
> recent version of the 25% in a single mass commit. This decreased the
> repository size to about 11gb.
> -----Original Message-----
> From: Kevin Greiner [mailto:greinerk@gmail.com]
> Sent: Friday, January 27, 2006 5:28 PM
> To: Dan White
> Cc: users@subversion.tigris.org
> Subject: Re: application ill-suited for svn?
> On 1/25/06, Dan White <dwhite@clubmom.com> wrote:
>> Unfortunately we didn't consider how repository
>> level versioning (which has no benefit in this application) would
>> inflate the db size. Some 6000 files, each only a few kb in size, and
>> 62000 revisions later, our /db/revs dir is about 19gb in size and
>> growing almost 1gb daily. We never have multiple file commits.
> This is the first I've heard about reposity level versioning inflating
> the db size. Could you elaborate? If I did my math right (19,000,000kb
> / 62,000 revs) you're averaging about 300kb per commit. That does seem
> high to me. And if you're growing at 1gb/day that means you're getting
> roughly 3,300 commits/day. That sound about right?
> I'm wondering if you could remove older revisions periodically? The
> dump file outputs revisions in date order but I don't know if you
> could chop off, say, the first 20,000 revisions without borking the
> resulting loaded repo or not. Anyone tried this?
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Received on Sun Jan 29 01:23:26 2006

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