Re: [Xen-users] High availability and live migration with just LVMand hardware fencing

[Bart Coninckx <bart.coninckx@xxxxxxxxxx>]

On Wednesday 19 May 2010 21:01:03 Javier Guerra Giraldez wrote:
> On Wed, May 19, 2010 at 1:27 PM, Bart Coninckx <bart.coninckx@xxxxxxxxxx> 
wrote:
> > What would you define as "change anything"? Add a LV?
> 
> for example, or expanding one, or deleting.  or adding a PV...
> 
> >  I suppose a "lvscan" on
> > every node would take care of the changes, no?
> 
> yes, but what about the time between the change and the lvscan on all
> nodes?  during that time, nonupdated nodes have a wrong idea of the VG
> structure, and that is deadly dangerous.
> 
> > Or does it mean I cannot  take
> > a snapshot? Or resize? Or all?
> 
> nothing that modifies the LVM metadata.
> 

I see ... Well, there are two good reasons I cannot have cLVM: need snapshots 
and it's simply not available for SELS10, so I'm going to keep on asking if 
permitted. 

- What if I would use a seperate volume group for every LV (and for every Xen 
guest)? Would that help? I suppose not really, since the Xen guest should be 
migratable, meaning that all nodes would need to have a consistent view no all 
VG's and LV's. 
- would snapshotting change the LVM meta data?

Cheers,


Bart

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