[vox-tech] Cloning LVM volume over network

[Brian Lavender]

On Tue, May 29, 2012 at 02:09:16PM -0700, Alex Mandel wrote:
> On 05/29/2012 11:36 AM, Brian Lavender wrote:
> > On Sun, May 27, 2012 at 09:16:24AM -0700, Wes Hardaker wrote:
> >> Alex Mandel <tech_dev at wildintellect.com> writes:
> >>
> >>> I'm looking for the most efficient way to clone an LVM volume 50GB from
> >>> one physical machine to another. Both machines must stay up, so that
> >>> rules out clonezilla. I'd also like it to be more efficient that dd, so
> >>> more similar to partimage or partclone where it skips the empty space
> >>> and only copies the filled part.
> >>>
> >>> Anyone have examples that show how to do this?
> >>
> >> I'd typically use rsync...  Fast and efficient :-)
> > 
> > Assuming the lvm volume is mounted on both sides and you tunnel rsync over ssh. 
> > If you are in an internal network, you could do it over rsh and avoid the crypto
> > overhead.
> > 
> > cd /mnt/local
> > 
> > Then use the the following from the rsync man page, clipped below. 
> > rsync uses the -e option for ssh, but I don't quite have a machine to test it.
> > 
> >  To synchronize my samba source trees use the following: 
> > 
> >                    rsync -Cavuzb . remote_machine:/mnt/local/
> > 
> > It is clipped from where Tridgell talks abut syncing his samba shares using
> > a Makefile and samba source code for CVS commits.
> > 
> > brian
> > 
> 
> I think the tricky part here is that the lvm volume may contain multiple
> partitions (I think it does have a / and a swap since it's a virtual
> machine disk), and I need the partition information, including the boot
> flags.

Hmm, with the Xen box I have configured, I have a logical volume per partition.
If I understand you correctly, you are putting more than one partition in each of
these logical volumes? What if you just put a partition per logical volume? This
way you can expand the logical volume and then the partition if need be while
the vm is running. 

I use xen tools to create my vms. It automatically creates the logical volumes
for the new vm. The system I have running, Dom0 runs on Debian and the VMs
are also running Debian. 

If for some reason I need to work on the VM while it is offline, I can mount it
using the following:

mount /dev/trout_pg/xen9.brie.com-disk /mnt/local

I am not sure if this will help in your situation but it might be worth consideration
for using an LV per partition.

root at trout:/home/brian# lvscan
  ACTIVE            '/dev/trout_pg/trout_lg0' [3.72 GiB] inherit
  ACTIVE            '/dev/trout_pg/trout_lg_root' [37.25 GiB] inherit
  ACTIVE            '/dev/trout_pg/xen9.brie.com-swap' [2.00 GiB] inherit
  ACTIVE            '/dev/trout_pg/xen9.brie.com-disk' [80.00 GiB] inherit

-- 
Brian Lavender
http://www.brie.com/brian/

"There are two ways of constructing a software design. One way is to
make it so simple that there are obviously no deficiencies. And the other
way is to make it so complicated that there are no obvious deficiencies."

Professor C. A. R. Hoare
The 1980 Turing award lecture