Comment 1 for bug 1934905

Problem is solved when such dirty hack is applied for os_brick: /usr/lib/python3/dist-packages/os_brick/initiator/connectors/iscsi.py:

--- /usr/lib/python3/dist-packages/os_brick/initiator/connectors/iscsi.py.orig 2021-07-23 15:17:13.999556010 +0200
+++ /usr/lib/python3/dist-packages/os_brick/initiator/connectors/iscsi.py 2021-07-23 15:14:09.355858606 +0200
@@ -1085,12 +1085,12 @@
     def _disconnect_from_iscsi_portal(self, connection_properties):
         self._iscsiadm_update(connection_properties, "node.startup", "manual",
                               check_exit_code=[0, 21, 255])
- self._run_iscsiadm(connection_properties, ("--logout",),
- check_exit_code=[0, 21, 255])
- self._run_iscsiadm(connection_properties, ('--op', 'delete'),
- check_exit_code=[0, 21, 255],
- attempts=5,
- delay_on_retry=True)
+# self._run_iscsiadm(connection_properties, ("--logout",),
+# check_exit_code=[0, 21, 255])
+# self._run_iscsiadm(connection_properties, ('--op', 'delete'),
+# check_exit_code=[0, 21, 255],
+# attempts=5,
+# delay_on_retry=True)

     def _disconnect_connection(self, connection_properties, connections, force,
                                exc):

Then backup is able to be created.