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Re: [Duplicity-talk] incremental database backup

From: Jacob Godserv
Subject: Re: [Duplicity-talk] incremental database backup
Date: Tue, 9 Mar 2010 16:05:33 -0500

(My answers need to be reviewed by someone more knowledgeable on this
list, but at least it'll give you some ideas.)

On Tue, Mar 9, 2010 at 14:24,  <address@hidden> wrote:
> I'm not sure where I've gone wrong, but I think my questions are:
> 1. does using a tgz archive mess up the incremental backup scheme?  is it
> possible that this will only work if I leave the databases in a
> (substantially larger) SQL format?

Yes. Duplicity actually does gzip compression by itself (if I recall correctly).

> 2. does allow-source-mismatch make up for the directory changes, or do I
> need to repattern our nightly backups so that duplicity can always take
> files from a directory of the same name?

Ah, the source mismatch might do it. Duplicity only diff's files that
belong to the same directory tree, so if the "list-current-files"
doesn't match the location you're backing up, then that's a problem.
I'm not sure how it behaves if you're backing up with a different root
directory but same root directory contents.

> And finally, one more (though perhaps I should put this in a separate
> e-mail?)
> 3. verify takes a very long time -- long enough that I eventually decided
> against using it as part of my regular backup scheme... is this normal?

In my experience, yes. My verification process is a separate sha512sum
which occurs right after duplicity finishes, and before any remote
uploading is completed. This is inadequate for highly sensitive data,
though, since it doesn't prevent against corruption during Duplicity's
backup operation.

The reason it takes so long is because duplicity essentially does a
"restore" and then diffs the data against the local copy. I'm pretty
sure it does as much as possible in memory to reduce disk I/O but I
could be wrong.


    "For then there will be great distress, unequaled
    from the beginning of the world until now — and never
    to be equaled again. If those days had not been cut
    short, no one would survive, but for the sake of the
    elect those days will be shortened."

    Are you ready?

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