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

[Sebastian Heinlein]

Quoting Sivan Greenberg <sivan at ubuntu.com>:

> Erast Benson wrote:
>
>> 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.
>
> I wasn't suggesting that it was not the right tool for the job, and I
> regret if that is what was implied from my reply. Lets take this further
> then, to make this work for the average user we need:
> 1) Use LVM by default to set up users system and storage.
> 2) Automatically create the LV that will store the snapshots for the
> user. This should probably be carried by a question to the user about
> how robust he wants his "going-back-in-time" ability and explain to him
> the proportional need for redundant disk space.
> 3) develop a simple UI on top of the tools to manage the snapshots such
> that it would be easy for the user to track changes, see in which
> snapshot the content he wants is, and allow him easily and safely return
> to any of the snapshots requiring minimum understanding to what goes
> behind the scenes in order to do so.
>
> So if this was to be a spec, it would have been dependant on an "Enable
> LVM by default" one. We should probably examine the situation in
> Fedora/Redhat to see the benefits and the downsides of enabling LVM by
> default.

Of course it would be nice to have the shadowing functionality of LVM. 
AFAIK lvm
allows to create a read-only device that represents the state of the 
LVM at the
snapshot time. So this would help us to avoid the problem of chaing 
data during
a perhaps quite long backup process.

Providing a time machine or pcbackup like functionality could be done a third
step. At first we need a robust and easy to use backup tool. I think a 
reuse or
cooperation with arnie [1] could be a good chance to this in the feisty time
frame. If this tool works, we could think about backing up not the real data,
but from a LVM snapshot device.

The transparent backup functionality is a little bit different. The main focus
is on providing a system wide version control system and not backing up. I
haven't taken a look at Roberts prototye, but an easy way to do this could be
to create a /Backup folder or a different parition/device and use hard 
links to
create an easy to access representation of older states in the file system:

/Backup/2006-11-11
/Backup/2006-11-9

Only changed files would be copied to newer backups. If the file hasn't 
changed
a hard link would be used.

So we would only a user interface with a "Back Up" button. The user could
restore his or her data by copying the corresponding files from the backup
directories.

Cheers,

Sebastian

[1] http://furius.ca/arnie/

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