Re: [libvirt] Quorum block driver libvirt support proposal

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

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 :|