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Re: Switching to Subversion

From: Juanma Barranquero
Subject: Re: Switching to Subversion
Date: Mon, 13 Nov 2006 02:20:28 +0100

On 11/13/06, Miles Bader <address@hidden> wrote:

subversion's official stance on the issue, that does not affect the bulk
of his arguments, which are based on rather fundamental issues.

For some definition of "rather fundamental issues." He mentions a good
feature of git:

"Files containing object data are never modified. Once written, every
file is read-only from that point forward."

but that's exactly what FSFS does. Then tries to make the off-line
compression of git pass as something good (which surely is, in *his*
setup, but not generally). Then rejects BDB off-hand (perhaps because
it would score better against some of his arguments), and considers
FSFS flawed because "[it] places one file per revision in a single
directory; a test import of Mozilla generated hundreds of thousands of
files in this directory, causing performance to plummet as more
revisions were imported". But having these files in a single directory
is not a *fundamental* property of FSFS; it can be easily changed, and
in fact there's been already talk of doing it. It would be trivial.

He continues: "I'm not sure what each file contains, but it seems like
revisions are written as deltas to an existing revision, making damage
to one file propagate down through generations", not having taken the
time to know how the revisions are stored; the complete text is saved
every N deltas (for a small N), so any possible corruption would not
be propagated. Funnily, then adds: "Lack of strong error detection
means such errors will be undetected by the repository. CVS used to
suffer badly from this when NFS would randomly zero out blocks of
files", which tries to suggest that SVN lacks strong error detection,
which he didn't demonstrate. Then he talks about the size of one
repository imported from CVS; but this is not the normal growing
pattern of a SVN repository (CVS has lots more commits because they
are not atomic). And he shows that he doesn't really know about
Subversion, because if he were, he could've talked of the size of
Subversion *working copies*, which can be two or more times the size
of the checked out files and have really generated some complains.

All in all, not many compelling arguments here, and quite a lot of
uninformed misrepresentations.

[If you are not familiar with git, I would recommend researching it,
it's a _very_ innovative system.]

I've never used it, but I've read some articles (and a few threads by
Linus Torvalds) about it.


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