The Friday 16 May 2014 à 09:54:43 (-0400), Daniel P. Berrange wrote : > On Fri, May 16, 2014 at 12:33:04PM +0200, Benoît Canet wrote: > > > > Hello list, > > > > > > > > I want to implement libvirt Quorum support. > > > > (https://github.com/qemu/qemu/commit/c88a1de51ab2f26a9a37ffc317249736de8c015c) > > > > Quorum is a QEMU RAID like block storage driver. > > > > Data are written on n replicas and when a read is done a comparison between > > the > > replica read is done. If more than threshold reads are identical the read > > succeed > > else it's and error. > > > > For example a Quorum with n = 3 and threshold = 2 would be made of three > > QCOW2 > > backing chains used as identicals replicas. threshold = 2 means that at > > least > > 2 replica must be identical when doing a read. > > > > > > > > I want to make use of the new backingStore xml element to implement quorum. > > > > > > > > Proposed Quorum libvirt format: > > > > ------------------------------- > > > > > > > > <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
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 ? Best regards Benoît > > > Regards, > Daniel > -- > |: http://berrange.com -o- http://www.flickr.com/photos/dberrange/ :| > |: http://libvirt.org -o- http://virt-manager.org :| > |: http://autobuild.org -o- http://search.cpan.org/~danberr/ :| > |: http://entangle-photo.org -o- http://live.gnome.org/gtk-vnc :| -- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list
