Prototype for the time machine similar solution as you noted in h-u-b whiteboard.

Aigars Mahinovs aigarius at
Fri Nov 17 09:11:13 GMT 2006

On 11/15/06, Erast Benson <erast at> wrote:
> On Wed, 2006-11-15 at 22:27 +0100, Ulrik Mikaelsson wrote:
> > Well my only thought is a reference to the old way of engineering, to
> > first decide what you want, and then use the tools that best suits
> > your needs to achieve it.
> >
> > Since I believe the "Time-Machine" use case to be one of the two
> > reasons why snapshotting in LVM were implemented, to me it seems like
> > the best suited tool.
> >
> > "Do the right thing, and do the thing right." It seems to me like a
> > time-machine is the right thing to do, and LVM is the right way to
> > achieve it, but I could be wrong. :)
> I think you are right. And LVM is the right place to do such things.
> Unfortunetly it is quite limited on functionality. OpenSolaris's ZFS
> would be way better fit, but it is not an option for GNU/Linux users at
> the moment.

LVM is the wrong place to do backup because it is too low level. There
are two features of all backup software - compressing backups and
(most important) excluding some files from backups. For example I
would not like to see my backup balloon each time I create a new 4.5
Gb DVD iso image and I do not want the backup to contain my 10+ Gb
FLAC collection as I backup it to other places (or can recreate from
the CDs). The same can be said about all other kind of temporary or
multimedia files.

The only correct way of implementing true Time Machine-like
functionality is to operate in the VFS level. That would require a
newsubsystem in the kernel, a user mode daemon and a very peculiar
security configuration if non-admin users are to allowed to change how
their files are to be backed up.

In short - it is way too much work even for feisty+1 and I really
wonder if it is worth it versus an incremental backup scheme with
logarithmic backup decay as already implemented in SBackup.

Best regards,
    Aigars Mahinovs        mailto:aigarius at
 |     .''`.         Debian GNU/Linux              LAKA         |
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 |    `. `'                                                     |
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