Re: [libvirt] Quorum block driver libvirt support proposal
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.
<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='block'>
<format type='qcow2'/>
<source dev='/var/lib/libvirt/images/file2.qcow2'/>
</backingStore>
<backingStore type='network'>
<format type='qcow2'/>
<source protocol='gluster' name='Volume1/Image'>
<host name='example.org'/>
</source>
</backingStore>
<target dev='vda' bus='virtio'/>
</disk>
--
Eric Blake eblake redhat com +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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