[linux-lvm] Still missing for supporting dm-thin

[Alasdair G Kergon]

On Mon, Jun 25, 2012 at 04:34:52PM +0200, Spelic wrote:
> 1) It is not possible to backup and restore a VG config (vgcfgrestore in  
> particular refuses to work) if there is a dm-thin volume. This is a very  
> serious problem that does not allow to recover even non-thin volumes if  
> there is a thin volume around. Even automatic backups from  
> /etc/lvm/archive cannot be restored/used. This puts data at risk, please  
> fix this.

We do want to find a way to do this for non-thin volumes - the current 
restrictions are indeed tighter than they need to be.

For thin volumes though it's a complex problem to work out what can
be restored safely and what can't.  (The metadata saying where a volume is is
now split between the LVM metadata and the thin metadata.)

> 2) less important: it is apparently not possible to change the --zero  
> flag for a thin pool once created. 

That should be just another lvchange parameter.

Alasdair