[linux-lvm] Which size for snapshot volume for a *safe* backup?

[Marc-Jano Knopp]

On Tue, 06 Dec 2005 at 01:10 (+0000), Alasdair G Kergon wrote:
> On Mon, Dec 05, 2005 at 11:39:11PM +0100, Marc-Jano Knopp wrote:
> > So, obviously,
> >   snapshot volume size = original volume size
> > is not sufficient to hold a complete change of the original volume.
>  
> Correct - there's a little bit of metadata required too to 
> map each piece of data back into the right location.

Thought so, just wasn't sure if it gets stored inside the volume or in
an extra file or device.


I have noticed that lvdisplay <snapshot volume> prints:

  Allocated to snapshot:   5.00%

But as I don't know the inner workings of LVM, I preferred not to take
this value for all variants of logical volumes for granted, but instead
ask here in this list for exact numbers.


[lvscan displays inactive snapshot volume as active]

> The 'lvs' attributes should be accurate (and lvdisplay too I think).
> lvscan doesn't check properly and needs fixing, thanks.

http://www.gotfuturama.com/Multimedia/EpisodeSounds/2ACV14/10.mp3

:-)


Best regards

  Marc-Jano