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Re: FAQ: svn advocacy / advice

From: Garrett Rooney <rooneg_at_electricjellyfish.net>
Date: 2005-11-08 04:02:13 CET

On 11/7/05, Kean Johnston <jkj@sco.com> wrote:

> 1. Is fsfs the prefered solution? If so, since each revision
> seems to be set of changes relative to the previous one,
> considering the amount of history and size of tree and
> number of revisions, does svn actually need to play back
> from revision 1 or does it store some sort of "checkpoint"
> along the way? If it does, is that automatic or manual?
> Also, if it does, is that "checkpoint" then basically the
> size of the repository at that point in time?

fsfs is the default repository back end these days, so I suppose you
could say it's "prefered". As for the deltas over large numbers of
changes, fsfs uses a technique called "skip deltas", which ensures
that you never have to apply more than log(n) deltas to get to any
particular revision, see
http://svn.collab.net/repos/svn/trunk/notes/skip-deltas for more
details.

> 2. I know there is a cvs to svn converter, and I've seen some
> threads about an SCCS to svn converter using cvs in between,
> but does anyone know of a direct SCCS to svn converter? If
> not, does svn's API lend itself to me writing such a tool?
> Anyone have any WAG what the scope of such a project would
> be?

I don't know of such a tool, but I imagine writing one would be
possible, although depending on how much of an impedence missmatch
there is between sccs and svn it could be difficult. CVS, for
example, took a considerable amount of effort.

> 3. Is it possible (even if slow) to check out a tree based on
> property values? For example, could I say "check out all
> files that have the property foo set to baz"? Or if not
> check out, at least get a listing of such files which I
> can then copy into a tag? (think: during the conversion
> process I retain SCCS info in properties, and then want
> to convert from a given SCCS SID to a propper svn tag).

This is not currently possible.

> 4. Has anyone ever done scalability testing with svn? Is it
> an appropriate tool for a 600 000+ source file repository?

There are several large scale svn repositories in the open source
world, for example the ASF repository
(http://svn.apache.org/repos/asf), the KDE repository (don't know the
URL off the top of my head), and most recently GCC (don't know the
URL, sorry). I don't know if any of those scale up to 600K source
files, but they're pretty big. In my experience, very large working
copies aren't exactly speedy, but if you limit commands to the section
of the tree you care about as much as possible svn will scale up
reasonably well. On the repository side there's certainly nothing
preventing that sort of scalability, assuming you aren't doing
something silly like putting all of those files in a single directory
;-)

I hope that helps answer your questions,

-garrett

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Received on Tue Nov 8 04:03:09 2005

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