[clue-admin] Backups

[Jab]

Dave,

I just signed up for this list so I only have part of the thread. That
said, with rdiff-backup you wouldn't have a tar a week. You would just
have new delta's. The performance difference being that you would only
copy that over the network once a week and it would only be the
delta's, not the whole file. (Like rsync instead of rdist or a tar
backup. I believe it does a block by block comparision.) Furthermore,
you can keep the deltas as long as you want or until the partition you
are backing up to fills up.

On your backup partition you would always have a current mirror and
then deltas going in reverse. This is a major benefit over traditional
backups where the farther you get from a level one the longer it takes
to restore. WIth the current mirror it is trivial to restore. I would
guess that with rdiff-backup you may be able to institute a nightly
backup without too much fuss.

I know some CU sysadmins have used rdiff-backup fairly sucessfully.
They rdiff-backup machines nightly and then on a weekly, monthly, or
quarterly basis back-up the mirror to tape. (With some of the deltas
if the tape will hold it.) In this way the tape bottleneck is
irrelevent because you are backing up off a mirror. No more coming
into a tape error and trying to re-run the backup. Or haviing the
spooling disk fill if amanda screws up.

-jacob

On 2/26/06, David L. Anselmi <anselmi at anselmi.us> wrote:
> Jeff Cann wrote:
> [...]
> > I thought rsync only sends changed / different files.  So after the first
> > 'full' backup of 75 MB, the next rsync would only send diffs.  I'm not sure
> > that rsync only sends changed blocks.  Plus rsync can compress on the fly...
>
> Yes, changed/different files.  We currently make a new tar file every
> week.  It's currently 75MB.  So rsyncing every week won't re-transfer
> the old tar files but it sends the new one entirely, 75MB.
>
> I think we can do better by using something other than tar files to hold
> the backup.  But I haven't yet figured out a way to explain the
> difference between tar and rdiff-backup that makes the performance
> difference obvious.  And I may be missing something (overhead other than
> network I/O, gzip compression vs. block sharing, etc.) that makes me wrong.
>
> Dave
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