[libvirt] Quorum block driver libvirt support proposal

[Daniel P. Berrange]

On Fri, May 16, 2014 at 08:18:36AM -0600, Eric Blake wrote:
> On 05/16/2014 07:54 AM, Daniel P. Berrange wrote:
> 
> >> <disk type='quorum' device='disk'>                                              
> >>   <driver name='qemu' type='quorum'/>                                           
> >>   <threshold value=2/>                                                          
> >>   <backingStore type='file'>                                                    
> >>     <format type='qcow2'/>                                                      
> >>     <source file='/var/lib/libvirt/images/file1.qcow2'/>                        
> >>   </backingStore>                                                               
> >>   <backingStore type='file'>                                                    
> >>     <format type='qcow2'/>                                                      
> >>     <source file='/var/lib/libvirt/images/file2.qcow2'/>                        
> >>   </backingStore>                                                               
> >>   <backingStore type='file'>                                                    
> >>     <format type='qcow2'/>                                                      
> >>     <source file='/var/lib/libvirt/images/file3.qcow2'/>                        
> >>   </backingStore>                                                               
> >>   <target dev='vda' bus='virtio'/>                                              
> >> </disk>
> > 
> > It feels rather odd to have <backingStore> elements but no top level
> > disk images. Really these are all top level images
> 
> Unfortunately, we are allowed to have a quorum with mixed-mode sources -
> I could have a quorum where file 1 is a local file, file 2 is a block
> device, and file 3 is a gluster protocol.  But since we encode the type
> of file at the <disk type='...'> level, there is NO way to list three
> different <source> elements for those three quorum members.  I think
> Benoit's proposal makes sense - a quorum is a node in the backing chain
> with NO <source> element, but instead has MULTIPLE <backingStore> elements.

Ok, I reluctantly agree.



Regards,
Daniel
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