Description of problem:

While configuring Ceph Mirroring, One of our Architect have discovered a bug in the cinder-volume service a bug in the cinder backup driver for Ceph.

In the file, $PYTHON_LIB/cinder/backup/drivers/ceph.py 

The _get_rbd_support() in cinder/backup/drivers/ceph.py is called whenever a new backup object is created. In this function, it only sets TWO features, layering and striping, and it DOES NOT reference the settings in /etc/ceph/ceph.conf. We need more than this feature for Ceph mirroring to work.

    def _get_rbd_support(self):
        """Determine RBD features supported by our version of librbd."""
        old_format = True
        features = 0
        if self._supports_layering:
            old_format = False
            features |= self.rbd.RBD_FEATURE_LAYERING
        if self._supports_stripingv2:
            old_format = False
            features |= self.rbd.RBD_FEATURE_STRIPINGV2



Version-Release number of selected component (if applicable):

RHSOP10

[heat-admin@laxmain-controller0 ~]$ rpm -qa | grep cinder
openstack-cinder-9.1.4-6.el7ost.noarch
python-cinderclient-1.9.0-6.el7ost.noarch
python-cinder-9.1.4-6.el7ost.noarch
puppet-cinder-9.5.0-2.el7ost.noarch



How reproducible:

To test that this is the problem, They forced the features to be 125 (for other services we set this in rbd_default_features in /etc/ceph/ceph.conf, but cinder-backup doesn't read this file for some reason). 

This looks like it MIGHT be fixed in upstream, but they have not tested the code as of yet:

~~~
http://git.openstack.org/cgit/openstack/cinder/tree/cinder/backup/drivers/ceph.py#n238
~~~

Cu would like to have a hotfix for this at the earliest convenience.