Tino Schwarze wrote:
> Hi Bowie,
>
> On Wed, Feb 18, 2009 at 12:26:16PM -0500, Bowie Bailey wrote:
>
> > > So, given that, I don't really understand why there is a
> > > distinction between a full and an incremental backup. Shouldn't
> > > either one take up the same amount of space? That is, if you've
> > > got few changes on the client, then on the server you're mostly
> > > just hardlinking things anyway, right? So why is there a choice?
> >
> > The result is basically the same, the difference is in
> > implementation. A full backup will compare the contents of every
> > file on the system to see if anything has changed. An incremental
> > will only check files whose change date has been updated since the
> > last backup.
>
> The last sentence is only true for non-rsync transfer methods, e.g.
> smb and tar. Rsync will detect any files which have been modified or
> added since the last run since it works by comparing file lists
> between server and client while samba and tar backup methods depend
> on the file's change times to detect changes.
Yea, I wasn't quite sure about that one. I know that an incremental
backup with Rsync is so much faster than a full because it doesn't check
everything, but I'm a bit fuzzy on the details.
> > I believe one of the main incremental backup issues is that they do
> > not detect deleted files. Incremental backups are also usually
> > MUCH faster than full backups. For example, one of my backups
> > takes about 600 minutes for a full backup, but only 56 minutes for
> > an incremental.
>
> Incrementals using rsync will detect deleted files correctly. I'm not
> sure about samba/tar.
I know that there is something that can get missed by an incremental
backup as a result of the way it works, I just don't remember exactly
what it is.
--
Bowie
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