[linux-lvm] moving a logical volume between servers

[Brad Sickler]

I'm surprised I couldn't find a good answer to the question before but I 
want to move logical volumes from one computer to another.

A little more detail... I created a bunch of xen images on logical 
volumes. I brought another computer up to split the load of all the 
virtual machines and I want to move some volumes to the new computer. 
When I created them I figured I could just dd them like a partition but 
upon attempting this and booting the transported xen machine/logical 
volume fsck showed some bad errors on the boot partition of the virtual 
machine. The later partitions seemed fine.

I did some testing and found that I got the same error no matter the 
block size. That if I created a new logical volume on the same machine 
as the source and dd'd between them ala
lvcreate -n machine2 -L 20G lvmxen
dd if=/dev/lvmxen/machine of=/dev/lvmxen/machine2
machine2 worked just like machine.
But when I dd'd to a file, moved that file to another computer then dd'd 
back into a new logical volume. I had the errors again.

I have some ideas on how to fix the error inside of the virtual machine 
but they would be painful considering that I have 10 virtual boxes 
running in this configuration.

So, I have a few questions for the lvm guru's.
A. Is it possible to move logical volumes from one computer to another? 
And no, these aren't simple ext3 file systems so I can't just mount it 
and export the files, they contain entire machines. I was hoping for 
something in the nature of lvexport / lvimport but that obviously 
doesn't exist.
B. Why does this occur?... I searched for a while but didn't find 
anything concrete as to why this occurs. I've always thought that a 
block device = a block device. Evidently I was wrong.

Thanks for any help.


Brad Sickler
Bioinformatician, Genome Center
University of California, Davis