Re: [Xen-users] LVM snapshot and xen stability

[Ernst Bachmann <e.bachmann@xxxxxxxx>]

On Friday 21 April 2006 15:43, Pasi Kärkkäinen wrote:
> On Fri, Apr 21, 2006 at 03:39:14PM +0200, Emiliano Gabrielli (aka AlberT) 
wrote:
> > Hi all,
> >   anybody has any info about stability of xen (3.0.2) configurations
> > using LVM2 r/w snapshots as domUs' physical disks?
> >
> > My intention is to test the possibility of having a template VM with a
> > base distro only and a number of snap-domUs with the differences for mail
> > server, web server and so on..
> >
> > Any experiences, tip and so on ??
> >
> > Tnx in advance
>
> Common understanding is that LVM2 snapshots are unstable - many people see
> crashes and problems with snapshots.
>
> I don't know if these problems are already fixed in Linux LVM..
>
> Maybe someone could post real world experiences.
>

My last try was very disappointing.

And even if they were perfectly stable, you'd have to face another problem:

You can't just update the "base" lv and have the changes appear in all 
snapshots (its block based).

So installing updates, security fixes etc always have to be done in each domU 
seperately, in the long run you won't save much disk-space and administration 
trouble with it.

Maybe have a look at unionfs, I'm running several domU's mounting their 
(shared) root-fs read-only over NFS, and then build an writable union with a 
seperate vbd in their initrds.

/Ernst

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