[CentOS] evaluating backup systems: rsync

Fri Jan 11 22:57:20 UTC 2013
Les Mikesell <lesmikesell at gmail.com>

On Fri, Jan 11, 2013 at 4:34 PM,  <m.roth at 5-cent.us> wrote:
> At any rate, the point is that the hard links point to *exactly* the same
> file on the disk, so it *looks* as though they take up equal space, but in
> reality, there's only one copy.
> So, if you're copying a directory to a timestamped named directory, and
> all the files except one or two being backed up haven't changed, then
> there's entries in both backup directories, but there's really only one
> physical copy, that of the one or two that are changed.

Rsync itself knows something about hardlinking against previous runs
if you use --link-dest=.   Backuppc goes it one (or several) better by
making an additional hardlink with a name based on a hash of the file
contents in a pool area.  Then any files with identical content are
linked to the same copy even if found in different places or from
different machines.   And it can store the data compressed and still
work with standard rsync clients on the target machines.

   Les Mikesell
      lesmikesell at gmail.com