Re: [linux-lvm] Is this possible with LVM?

[Lothar Werzinger <lothar@tradescape.biz>]

On Wednesday 15 August 2007 13:18, Bryn M. Reeves wrote:
> Lothar Werzinger wrote:
> > What I would like to do is to unmount LV2 and be able to remove the
> > external disk from the Ultrabay to replace it with a DVD drive while
> > still be able to acess the filesystem on LV1 (which uses only space on
> > the internal disk). I would like to do this to backup data from LV1 to
> > DVD-RW.
> >
> > Is this possible with LVM? How would I go and prepare the external disk
> > for removal? How would I reconnect if I insert the disk again.
>
> It is possible, but not with both PVs in the same VG (well, not unless
> you want to be doing a lot of manual tweaking and fiddling as you
> plug/unplug the external drive and even then you would need to be
> extremely careful when changing/resizing LVs - basically, don't! :).
>
> If you put LV2 in its own VG then you can achieve exactly what you
> describe via:
>
> umount /path/to/LV2
> vgchange -an VG2
>
> Then remove the external disk. Optionally, you could mark the VG as
> exported with vgexport if you wanted to move it between different hosts.
>
> To re-activate it, plug it back in and re-activate it:
>
> vgchange -ay VG2
>
> Preceding that with a vgimport if you did choose to export the VG.
>
> Depending on the versions of the tools you are using and they way you
> configured the physical volumes when you set them up you can probably
> break the VG up using vgsplit.

I read the manpage to vgsplit and I am lost :-(
Can two VGs use the same PV? How do they know how to share the space?

can you give an example on how I might use vgsplit?

Here's the version I used:
vgcreate --version
  LVM version:     2.02.26 (2007-06-15)
  Library version: 1.02.20 (2007-06-15)
  Driver version:  4.11.0

> Kind regards,
> Bryn.

Lothar