Currently, the overcloud is blocked during the duration of the backup process. A three node (HA) controller plane should be able to continue operating while a consistent backup process is being done.
Since the problem described in this bug report should be resolved in a recent advisory, it has been closed with a resolution of ERRATA. For information on the advisory (Release of components for Red Hat OpenStack Platform 16.2.1 (Train)), and where to find the updated files, follow the link below. If the solution does not work for you, open a new bug report. https://access.redhat.com/errata/RHBA-2021:5067