https://access.redhat.com/documentation/en-us/red_hat_openstack_platform/17.1/html-single/framework_for_upgrades_16.2_to_17.1/index#upgrading-to-ceph-storage-5-upgrading-ceph

Please review if it would be possible to add known issues during the upgrade:

For example, the customer upgrading from Ceph 4 to Ceph 5, one of the monitor upgraded to Ceph 5, while the others are still on Ceph 4 and restarting.

https://access.redhat.com/solutions/7020523

Ceph team may help with wording this better, but solution is not visible enough to the customers following our documentation.