Date: Sat, 22 Mar 2008 02:10:01 +0200 From: Giorgos Keramidas <keramida@ceid.upatras.gr> To: d@delphij.net Cc: freebsd-hackers@freebsd.org Subject: Re: Some versioned storage program? Message-ID: <874pazpqjq.fsf@kobe.laptop> In-Reply-To: <47E4405E.2080609@delphij.net> (Xin LI's message of "Fri, 21 Mar 2008 16:10:22 -0700") References: <47E4405E.2080609@delphij.net>
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On Fri, 21 Mar 2008 16:10:22 -0700, Xin LI <delphij@delphij.net> wrote:
> Hi, folks,
>
> I'm looking for some versioned storage program that can fulfill the
> following requirements:
>
> - Open source/Free Software that can run on FreeBSD, or not far
> (i.e. on other POSIX OS)
> - Support of atomic commit/rollback.
> - Fast checkin time (At least, when added/changed files are explicitly
> specified).
> - Fast update time (i.e. something like 'cvsup -s' that makes it
> possible to trust bookkeeping file rather than stat'ing every files)
> - Scalable for a large number of files, directories and revisions. Say,
> it is not acceptable for it to store a zillion of revisions as
> individual files within one directory.
> - Ideally it can support some sort of "hook" functions upon commit so
> that changes can be notified in some way such as e-mail.
> - Ideally it can support fast export of a snapshot for HEAD and
> "nearby" revision like HEAD - 1, etc.
>
> I think what I need is some SCM software like subversion or hg, but I do
> not know if there is some superior stuff that matches these requirements
> better. Any other suggestions?
Before you start using Hg, Git or Subversion it may be worth
experimenting a bit with them. My apologies if you _have_ already and
the previous sentence sounds patronising. All I'm saying is that they
all have a fair share of good, not so good, or even bad aspects. So it
would be nice to have tried them all a bit and pick the one that seems
like the best fit for the job at hand :)
To provide a few starting points:
- Subversion, Git and Hg, all run on FreeBSD
- They support 'changesets' as the basic model of storing commits
- Commit speed varies a bit. For locally stored 'workspaces', Git and
Hg seem to be more or less equally fast, with Subversion being a close
second
- Update times tend to vary a bit too. Hg and Git will blow Subversion
away on locally stored repositories, but they might suck a bit on NFS
workspaces
- Storing individual revisions as 'a zillion directory entries in a
single tree' seem to point at Subversion. Have you already tried it,
and found that it doesn't scale for your sort of work? It is used by
many large-ish projects, so it would be surprising but not unrealistic
to have scalability issues after a few million commits
- Hooks _are_ supported by Subversion, Git and Hg (others too)
- Checkout speed (and `export' speed) is pretty fast in Git and Hg.
Subversion is a bit slower, but still usable. Changeset support is a
nice feature, because it doesn't matter if your `export' run takes 1.5
minutes instead of 20 seconds. When a given changeset is exported in
any of svn/git/hg you _never_ get a mix of file revisions from
changesets ${FOO} ... ${FOO+j} for some arbitrarily random value of
'j', because 'j+k' commits happened in the mean time.
Before you _do_ embark on the journey of using a VCS for storing a bunch
of files, it would be nice to stop for a moment and consider if you need
one. If you do, there _are_ options, and they are definitely not
limited to the three systems mentioned so far.
HTH,
Giorgos
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