doc: note cinder multi-backend restriction

Signed-off-by: Josh Durgin <josh.durgin@inktank.com>

diff --git a/doc/rbd/rbd-openstack.rst b/doc/rbd/rbd-openstack.rst
index a5e91c31b1a6a43c606cd0e307762ac275c880b8..92b67ea1a1efbb59a3fc0129cdd53721110a34a2 100644 (file)
--- a/doc/rbd/rbd-openstack.rst
+++ b/doc/rbd/rbd-openstack.rst
@@ -211,6 +211,9 @@ uuid of the secret you added to ``libvirt`` as documented earlier::
     rbd_user=cinder
     rbd_secret_uuid=457eb676-33da-42ec-9a8c-9293d545c337
 
+Note that if you are configuring multiple cinder back ends,
+``glance_api_version=2`` must be in the ``[DEFAULT]`` section.
+
 
 Configuring Cinder Backup
 -------------------------