Re: device mapper help

[William Thompson <wt@electro-mechanical.com>]

On Fri, Nov 07, 2008 at 11:44:00PM +0800, hhding.gnu wrote:
> William Thompson wrote:
> > I'm not on the list.  Please always keep me in the CC.
> > 
> > Is there a tool somewhere that will allow me to merge a snapshot into the
> > parent device?
> > 
> > For instance, if I have a snapshot of /dev/sdb like this:
> > sdb-snap1: 0 16777216 snapshot /dev/sdb /dev/sdb-snap1-backing P 8
> > sdb-snap2: 0 16777216 snapshot /dev/sdb-snap1 /dev/sdb-snap2-backing P 8
> > ...
> > 
> > Lets say that I want to update sdb with the data in /dev/sdb-snap1-backing. 
> > What would I do to do this?  Is there some tool that does this?  I
> > understand that there can be problems with snapshots of snapshots like this,
> > but that is not the question.
> > 
> > 
> As far as I know, LVM does not provide this function. ZFS can promote
> it's snapshoot.

I'm not using LVM for this functionality.  I want this on the block level,
not the fs level.