[libvirt] Quorum block driver libvirt support proposal

[Benoît Canet]

The Friday 16 May 2014 à 08:20:22 (-0600), Eric Blake wrote :
> On 05/16/2014 08:07 AM, Peter Krempa wrote:
> 
> >>>
> >>> It feels rather odd to have <backingStore> elements but no top level
> >>> disk images. Really these are all top level images
> >>
> >> It reflect the ways QEMU does it. A single BlockDriverState holding n
> >> quorum BlockDriverState children. There is a 1-1 mapping.
> >>
> >> How would you see it ?
> > 
> > We'd rather see multiple source elements for the top level disk. Backing
> > store is the property of the source image, thus every single of those
> > sources should have it's own list. (or perhaps a tree?)
> 
> I don't see how you can possibly have multiple source elements.
> Remember, part of the determination of what forms a valid <source>
> element is the type='...' attribute tied to the <disk> parent element -
> but you can't have duplicate attributes.  As I see it, a quorum HAS to
> be a special chain element with 0 sources and multiple backingStore
> children, where each backingStore then includes the type='...' attribute
> for how to interpret the <source> element of that child.

Additionally quorum support taking snapshots so we need one entity to
bind them together.

Best regards

Benoît

> 
> -- 
> Eric Blake   eblake redhat com    +1-919-301-3266
> Libvirt virtualization library http://libvirt.org
> 



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