[CentOS] Rsync and differential Backups

Mon Nov 9 19:34:50 UTC 2015
Valeri Galtsev <galtsev at kicp.uchicago.edu>

On Mon, November 9, 2015 12:42 pm, m.roth at 5-cent.us wrote:
> Gordon Messmer wrote:
>> On 11/09/2015 09:59 AM, John R Pierce wrote:
>>> On 11/9/2015 9:50 AM, Gordon Messmer wrote:
>>>> I don't see the distinction you're making.
>>> a incremental backup copies everything since the last incremental
>>> a differential copies everything since the last full.
>> I guess that makes sense, but in backup systems based on rsync and hard
>> links (such as rsnapshot), *every* backup on the backup volume is a
>> "full" backup, so incremental and differential are the same thing.
>>> rsync is NOT a backup system, its just a incremental file copy
>> ..which can be used as a component of a backup system, such as rsnapshot
>> or backuppc.
> Actually, we use rsync for backups. We have a script that creates a new
> daily directory... and uses hard links to previous dates. That way, it
> looks like a full b/u... but you can go to a previous date to restore an
> older version of the file (aka ACK! I saved that file full of garbage to
> my Great American Novel filename! <g>).

I wonder how filesystem behaves when almost every file has some 400 hard
links to it. (thinking in terms of a year worth of daily backups).


> And if you aren't familiar with hard links, which rsync happily creates,
> they were certainly hard enough to wrap my head around, until I got it...
> and really like them. Just note that they *must* be on one filesystem, as
> opposed to symlinks, which can cross filesystems.
>         mark
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Valeri Galtsev
Sr System Administrator
Department of Astronomy and Astrophysics
Kavli Institute for Cosmological Physics
University of Chicago
Phone: 773-702-4247