[linux-lvm] rw-snapshot as an addition for lvm

[Joe Thornber]

On Mon, Jul 30, 2001 at 11:28:18AM +0200, Jos Visser wrote:
> The question I would have is whether rw-snapshots (or, snapshots in
> general), should be implemented in LVM or as a separate driver/layer. In
> that case, a snapshot could be taken of any block device, not only of a
> logical volume.

Yes, I've already raised this issue... and written a new standalone
driver, which will go into experimental soon :) There's a similar
argument that multi-pathing is standalone.

> 
> Another interesting feature that I might add that would be handy here is
> the "dynamic LV". This would be a LV that can extend dynamically if so
> requested. The advantage of this would be that you could use the dynamic
> LV as the buffer space of a snapshot. If the snapshot requires more
> space, the LV could extend dynamically to allow for this....

There are facilities for monitoring snapshot usage.  You could easily
write a script that extends the lv when it hits, say, 90 % full.

- Joe

> 
> ++Jos
> 
> And thus it came to pass that Joe Thornber wrote:
> (on Mon, Jul 30, 2001 at 10:57:26AM +0100 to be exact)
> 
> > On Sat, Jul 28, 2001 at 06:27:41PM +0200, Anders Henke wrote:
> > > I think it's also quite interesting to have a rw-snapshot in which changes
> > > of both real and snapshot are being written to a smaller bufferspace on disk:
> > > the snapshot always represents the state of the LV when taking the snapshot,
> > > but permits changes on 'its copy'.
> > 
> > See other thread in the last few days on rw snapshots;  Yes, it's an
> > execellent idea.
> > 
> > - Joe
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> 
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