[OpenAFS] Incremental backups

Fri, 25 Apr 2008 11:50:23 -0600

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Tom Fitzgerald wrote:
> Can someone confirm that my assumptions about incremental AFS
> backups are correct?
> 
> 1) Aside from needlessly increasing the size of the dump, there's
>    no harm in setting the -time of an incremental dump to be
>    substantially earlier than it needs to be.
In my experience, you are correct.
> 
> 2) If I do a "vos backup X" and later a "vos dump X.backup", then
>    later a incremental dump, the -time in the incremental dump
>    should be the time of the first "vos backup" (or earlier), not
>    the full "vos dump". 
Yes, but before you do the incremental dump, you need to do another
vos backup ;)

Depending on your incremental strategy there are a few more
issues to consider.

If your incrementals are partial (e.g. changes since the
last incremental backup) then you need to ensure that the
vos backup before each incremental actually works, or you
may create a "hole" in your backup data.  We also ran into
problems with time between running on the command line vs.
cron.  Our software compares time stamps in the vos dump
headers to avoid these types of problems.

If your incrementals are cumulative (e.g. changes since
the last full), then if any given vos backup fails, the
next incremental will simply be another copy of the
previous incremental.  You will miss that days changes.
As long as the vos backup problem does not persist, your next
backup should "catch up".

> 
> 3) vos dump X "01/01/2008"
>    is the same as
>    vos dump X "01/01/2008 00:00"
This seems to be correct.  I ran two test dumps and used
our afsvcheck program to look at the dump header.

vos dump vol.backup -time "04/24/2008" -file 1
afsvcheck -f 1 -v | grep From
 From [0] = 1209009600: Thu Apr 24 00:00:00 2008

vos dump vol.backup -time "04/24/2008 00:00" -file 2
afsvcheck -f 2 -v | grep From
 From [0] = 1209009600: Thu Apr 24 00:00:00 2008

Which also makes sense intuitively.

Kris
> 
> In honor of the Evansville, IN school district which lost four
> weeks of high school grade information due to "an unfortunate
> and very rare combination of hardware problems and backup
> configuration settings", I'm sanity-checking all my backup scripts.
> 
> Thanks for any info.
> 
> 
> _______________________________________________
> OpenAFS-info mailing list
> OpenAFS-info@openafs.org
> https://lists.openafs.org/mailman/listinfo/openafs-info
> 
> 

-- 
Mr. Kristen J. Webb
Teradactyl LLC.

PHONE: 1-505-242-1091
EMAIL: kwebb@teradactyl.com
VISIT: http://www.teradactyl.com

  	Home of the

  True incremental Backup System

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