Re: mirror and snapshot incompatible

[Yoav <ml-lvm@hidden.domain.name>]

I know how to do it through device-mapper.  I'm just worried that maybe 
there's a reason why lvm prevents it.  Are you aware of such reason, or 
is it safe?

Jonathan Brassow wrote:
> It is possible to do all the things you are asking through 
> device-mapper... but there is no easy way to do it.  (and LVM does not 
> yet have the capabilities to manage this yet either.)
>
>  brassow
>
> On Oct 27, 2008, at 9:28 PM, Yoav wrote:
>
> > According to lvcreate, a snapshot of a mirrored volume cannot be 
> > created ("Snapshots and mirrors may not yet be mixed").  However, 
> > devmapper does not seem to have the same limitation when used 
> > directly (not through lvm).
> >
> > Is there a current reason for lvcreate to enforce this rather harsh 
> > limitation?
> >
> > What are the risks I'm taking by manually creating a dm-snapshot from 
> > a dm-mirror device?  (of course I'm also replacing the dm-mirror 
> > device with a snapshot-origin of the actual dm-mirror device).
> >
> > If there is an actual reason for preventing this, what is the 
> > suggested way to consistently backup a mirror volume?  Is there a way 
> > to temporarily take one of the mirror "legs" (mimage devices)  
> > offline in order to back it up, and resync it later?
> >
> >   Yoav
> >
> > _______________________________________________
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> > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
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