On Tue, May 18, 2004 at 10:06:52AM -0400, Alberto Accomazzi wrote:
> Chris Shoemaker wrote:
>
> > Indeed, what you describe seems to have been the design motivation.
> > I
> >can share what my desired application is: I want to create a mirror of a
> >public server onto my local machine which physically disconnected from the
> >Internet, and keep it current. So, I intend to first rsync update my own
> >copy
> >which _is_ networked while creating the batch set. Then I can sneakernet
> >the
> >batch set to the unnetworked machine and use rsync --read-batch to update
> >it. This keeps the batch sets smallish even though the mirror is largish.
>
> This was something I looked into a couple of years ago. Back then I
> even posted an email to the list
> (http://lists.samba.org/archive/rsync/2002-August/003433.html) and got
> no feedback, which led me to conclude that people were not doing any of
Reading that post was like reading something I could have written just
last week. :) I'm sorry you didn't get any response. Things must have
picked up around here. You, Wayne and Jos have been quite responsive to my
recent questions and comments.
> this at the time. To restate the obvious, the batch mode thing is
> really just a glorified diff/patch operation. The problem I have with
> it is that AFAICT it's a very fragile one, since a simple change of one
> file on either sender or receiver after the batch has been created will
> invalidate the use of the batch mode. Contrast this with diff/patch,
> which has builtin measures to account for fuzzy matches and therefore
> makes it a much more robust tool.
You're right about the fragility, but under some conditions the
constraints can be met.
>
> In the end my motivation for using the rsync-via-sneakernet approach
> disappeared when I convinced myself that the whole operation would have
> been far too unreliable, at least for our application where files are
> updated all the time and there is never really a "freeze" of a release
> against which a batch file can be created. I won't go as far as saying
Well, what did you do instead?
> that the feature is useless, but just caution people that they need to
> understand the assumptions that this use of rsync is based upon. Also,
> I would suggest checking out other diff/patch tools such as rdiff-backup
> or xdelta.
I looked at theses but didn't see how they could help me in my
situation (same as what you described). Am I missing something?
>
> > BTW, there is a work-around. If you don't mind duplicating the
> > mirror
> >twice, one solution is to do a regular (no --write-batch) rsync update of
> >one
> >copy of the mirror, and then do the --write-batch during a local to local
> >rsync update of another copy of the mirror. Actually, this has some real
> >advantages if your network connection is unreliable.
>
> This is really the only circumstance under which I would even consider
> using batch mode. There should also be safeguards built into the batch
> mode operation to guarantee that the source files to which the batch is
> applied are in the state we expect them to be. I wouldn't otherwise
> want rsync to touch my files.
Good point.
-chris
>
> > Thanks for your input.
>
> Likewise. Good luck...
>
> -- Alberto
>
>
> ********************************************************************
> Alberto Accomazzi aaccomazzi(at)cfa harvard edu
> NASA Astrophysics Data System ads.harvard.edu
> Harvard-Smithsonian Center for Astrophysics www.cfa.harvard.edu
> 60 Garden St, MS 31, Cambridge, MA 02138, USA
> ********************************************************************
>
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