[linux-lvm] Is this possible with LVM?

[linux-lvm] Is this possible with LVM?

[Lothar Werzinger]

Hi,

I have a Lenovo Thinkpad T61 with a second disk drive for the Ultrabay.

I created one PV on the internal and external (Ultrabay) each
I created a VG with these two PVs.
I created a LV (LV1) that uses exclusively PV intern
I created a LV (LV2) that uses both PVs in striped mode.

So far everything works fine.

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.

Thanks in advance!

Lothar

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

[Bryn M. Reeves]

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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.

Kind regards,
Bryn.

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

[Lothar Werzinger]

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