Thanks for clarifying this Erik. Let me point out then that the release notes [1] are worded rather unequivocally, and what you are saying contradicts them:

RBD driver has added multiattach support. It should be noted that replication and multiattach are mutually exclusive, so a single RBD volume can only be configured to support one of these features at a time. Additionally, RBD image features are not preserved which prevents a volume being retyped from multiattach to another type. This limitation is temporary and will be addressed soon.

Bernd.

On 5/28/2019 11:30 AM, Erik McCormick wrote:

There isn't really a Ceph multi-attach feature using Cinder

[1] https://docs.openstack.org/releasenotes/cinder/stein.html