Re: [Duplicity-talk] Resumption and fulls with large backups.

[Robin Lee Powell]

On Tue, Aug 11, 2009 at 01:13:48PM -0500, Kenneth Loafman wrote:
> Robin Lee Powell wrote:
> > I see from
> > http://lists.gnu.org/archive/html/duplicity-talk/2008-12/msg00057.html
> > that 6 months or so ago Duplicity did not have the ability to
> > resume failed backups.  Is that still the case?
> 
> That's a rather old message, last year in fact.  As of the 0.6.xx
> series, duplicity can now resume a failed backup.

Ah, good to know.  Thanks.

> > A related question, in as much as it matters a lot for very large
> > backups: do full backups re-use files from previous fulls?  That is:
> > does every full backup imply/require copying all the data from
> > scratch again?
> 
> A full backup, by definition, backs up all the files, so yes, a full
> backup copies all the files.  

Yes, but many backup system look at the previous full, and keep
files that haven't changed, without retransmitting.  We're talking
about 700 GiB of data; copying all of 700GiB (to S3 no less) takes a
*very* long time.

A full, by definition, has all the files within it, but that's not
necessarily the same thing as retransmitting all of them.

> Let me explain myself, I have never backed up a full disk in my
> life, and that's 40+ years in this field.  To me, a FULL backup is
> a complete backup of the DATA on the disk, nothing more.  To
> backup something that is on an install CD is a waste of time,
> especially in todays environment of high bandwidth networks.  I've
> never lost data and quite often a failed disk was a blessing
> because I could take the time to upgrade.

We're only copying the data generated by the application; we're not
touching the OS at all.

-Robin

-- 
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