The Stein release notes mention that the RBD driver now supports multiattach, but i have not found any details. Are there limitations? Is there a need to configure anything?

In the RBD driver, I find this:

    def _enable_multiattach(self, volume):
        multipath_feature_exclusions = [
            self.rbd.RBD_FEATURE_JOURNALING,
            self.rbd.RBD_FEATURE_FAST_DIFF,
            self.rbd.RBD_FEATURE_OBJECT_MAP,
            self.rbd.RBD_FEATURE_EXCLUSIVE_LOCK,
        ]

This seems to mean that journaling and other features (to me, it's not quite clear what they are) will be automatically disabled when switching on multiattachment.

Further down in the code I see that replication and multiattach are mutually exclusive.

Is there some documentation about the Ceph multiattach feature, even an email thread?

Thanks,

Bernd