On Sun, 20 Jun 2010 19:41:34 -0400, Mike Kallies <mike.kallies AT gmail DOT com>
wrote:
> Hello Everyone,
> 
> I've been using BackupPC in production and at home enviornments for the
> past couple years.  It's a great program, but I'll add that it takes a
> while to get the hang of how it does things.
> 
> So here's my question.  Is it necessary to take a full backup at a
> regular interval?  I mean, can't BackupPC fill-in the incrementals to
> simulate a "full" then do a superficial compare of the backup directory
> tree against the client's directory tree (e.g., compare the
> date/time/size/attributes)?  Sort of "flattening" an incremental?
> 
> I want to do this because I'm currently setting up BackupPC to use rsync
> to keep backups of hosted website.  By default, my backup policy is
> going to take a "full" backup every week.  This is going to transfer 1GB
> of data every week... that's not ideal.  The web host isn't going to
> like me, and it shouldn't be necessary for me to transfer that much
data.

Ah - when using 'rsync' or 'rsyncd' as the transport, backuppc has a
slightly different notion of what a "full" backup is than other backup
software.

When using rsync, only the block differences are EVER sent across the wire
(unless you add '--whole-files' to the cmdline, IIRC). In backuppc, the
only difference between a full and an incremental is how rsync determines
what data to send. In an incremental, files are checked via last-modified
time; in a full backups, a block-level compare is done across all files.
This means the only real performance hit on a full backup is that the
client rsync must read every block of every file -- but no extra data is
sent across the wire.

-Josh

-- 
--------------------------------------------------------
       Joshua Malone       Systems Administrator
     (jmalone AT nrao DOT edu)    NRAO Charlottesville
        434-296-0263         www.cv.nrao.edu
        434-249-5699 (mobile)
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