[NCLUG] Server-to-Server backups

Sean Reifschneider jafo at tummy.com
Tue Jun 27 00:26:57 MDT 2006


On Mon, Jun 26, 2006 at 07:19:11PM -0700, Stephen Warren wrote:
>It's also pretty easy to store N recent hard-linked copies for backup
>history too - either via pre-written solutions like

There are, of course, a few problems with this.  One is that if you are
talking a lot of files, it can take a long time to create and delete the
hard linked copies.  Also, if you have a big database or log file that is
big with appends adding to it, this mechanism will consume the unchanging
part for every copy.  A 2GB file that's appended to by 100KB every day, and
rsynced every day for a week will consume 14GB of real disc space.

rdiff-backup is another tool that you might want to look at.  It's super
picky about the same version running on both ends of the link, but with two
systems it shouldn't be an issue.  rdiff-backup uses the low-level rsync
protocol and stores basically the rsync data stream.  rsync has an option
to do this, but I've never had luck with it.

So, you do one full rdiff-backup, and then you do incrementals.  I think it
keeps the most recent copy, and then the transaction streams can be
replayed to go back to older versions of files and the file-system.  In the
2GB file example above, it only uses 2GB+(100KB*7*2) of space or so.
Deleting old incrementals is fast and easy.

That said, I stopped using it on my laptop because they were failing and I
couldn't get them working again.  I went back to the rsync mechanism that
we use for other systems.

As far as the time it takes to push them across the wire: who cares?  I've
some some backups that took the better part of a week to get the initial
data synced across (slow DSL uplink, and/or lots of data).  Once the
initial sync is done though, the backups of daily data usually take just an
hour or two at night.

Sean
-- 
 I would rather suffer defeat than have cause to be ashamed of victory.
                 -- Quintus Curtius
Sean Reifschneider, Member of Technical Staff <jafo at tummy.com>
tummy.com, ltd. - Linux Consulting since 1995: Ask me about High Availability




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