Re: [Duplicity-talk] Direct backup of LVM snapshot partitions?

[edgar . soldin]

On 07.12.2012 19:01, George MacKerron wrote:
> Hi all.
> 
> I'm trying to use duplicity to back up LVM snapshots (which are Xen domU 
> disks). 
> 
> I've seen scripts that take a snapshot, mount the snapshot, and then back up 
> the files inside it. But my preference is to just back up the LVM logical 
> volume directly. I feel more comfortable knowing I have an exact, 
> filesystem-level snapshot.

that's what a snapshot is.where do you figure a difference between the snapshot 
and the parent logical device, except of the static nature of the snapshot 
though?
 
> However, this doesn't appear to work: if I specify a volume such as 
> /dev/dm-10, this isn't backed up. So at the moment I am using dd to copy the 
> volume data to a temporary file, and then using Duplicity on this. However, 
> this causes a lot of seemingly unnecessary disk thrashing.

first.. to backup a device node makes no sense. these are just special files 
with no actual content except of some metadata meaningful to (kernel)software 
only.
http://en.wikipedia.org/wiki/Device_file

secondly, what you want is the snapshot. it allows you access without copying 
first.

finally: you can of course always access your data where you mounted it in the 
first place, hence in the vms you are running and run your backup in there.

so understand, device nodes have to be mounted (or dumped;) in order to access 
their data.

..ede/duply.net