[linux-lvm] using LVM from two machines

[Patrick Caulfield]

On Wed, Aug 01, 2001 at 08:24:51AM -0700, Aman Shahi wrote:
> Hi,
> I have LVM installed on two machines, both of which
> are connected to the same storage(RAID BOX). Now I
> need to do LVM operations from different machines at
> different times. I will try to put a scenario and my
> problem.
> 
> Lets say I have 2 disks( disk1, disk2). I have two
> machines M1 and M2. Both machine see all the disks. If
> I create a VG called VG1 on disk1 from M1, and do a
> vgscan on M2, the VG VG1 can be seen from both the
> machines. I then create VG called VG2 from M2 on
> disk2.
> 
> So basically I created 2 VG's from two different
> machines, but both is visible on both machines. 
> 
> Now if I delete a VG from a machine from one machine,
> any LVM operations from the other machine fails with
> the message "VGDA in kernel and LVMTAB are not
> consistent". I manually removed /dev/VG1 and /etc/lvm*
> from the other machine and did a vgscan , but still I
> get the message "VGDA in kernel and lvmtab are
> inconsistent, please run vgscan". Running vgscan does
> not help.
> 
> How can I modify this VGDA in kernel in the other
> machine so that any LVM operation on one machine can
> be reflected in the other machine. Or can I do
> something like  "deactivating" the data that is kept
> in the kernel, so that the LVM just relies on the
> information in the disks, or something like that. I
> mean I need to be able to use LVM from two different
> machine as if they were one.

The short answer is "don't do that!". We are currently working
of a cluster-enabled version of LVM (I don't have any release dates I'm afraid)
that will enable you to do what you want and more.

The only way to achieve what you want to do at the moment is to unload the VGs
on one machine (vgchange -ay after closing all the volumes), make the changes
on the other machine and then re-run vgscan on the first machine and remount the
volumes. This applies to *any* changes you make to the LVM configuration.

Be careful !

patrick