[Discuss] mirroring with rsync

[Alan W. Irwin]

On 2006-06-08 01:04+0100 Andy Davidson wrote:

> I would start with an empty local directory so that the --delete was not
> needed personally.
>
>
>> From your mail, it would sound to me like you understand everything you
> need to in order to get your backups working though.  I tend to use
> rsync rather than scp for copies because rsync has had resumes for
> longer .. but they are similar in interface behaviour, really.

Thanks for your reply, Andy.

I feel much more confident now because I gained some experience since my
question to this list.

For example, I went ahead and tried --delete and is does work (although it's
dangerous if you screw up your directories).  The reason it is needed is
that the remote tree (in this case the SourceForge CVS repository) does have
files removed from it from time to time, and you absolutely want your local
tree to reflect those deletions.  You could do that by using scp and
starting fresh each each time with an empty directory. Of course the first
rsync is normally done that way as well, but it is not necessary on second
and subsequent times.  In fact it is preferred not to remove the local tree
after the first rsync.  Then you gain typically factors of 300 or so over
what scp can do since relatively few bytes of bandwidth are normally needed
by rsync to keep a local _existing_ tree in exact sync (including deletes)
with the remote tree.

Alan
__________________________
Alan W. Irwin

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the FreeEOS equation-of-state implementation
for stellar interiors (freeeos.sf.net); PLplot scientific plotting software
package (plplot.org); the Yorick front-end to PLplot (yplot.sf.net); the
Loads of Linux Links project (loll.sf.net); and the Linux Brochure Project
(lbproject.sf.net).
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Linux-powered Science
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