Hi again. I'm answering my own question. It seems I read the wrong version of the doc ... sic! It should be enough to set the “_admin” flag on all nodes: and that we also need to install cephadm on the nodes we want to use for administration, right!? -- M Michel Le Cocq via ceph-users <ceph-users@ceph.io> writes:

Hi all,

I am currently deploying a Ceph cluster with cephadm on 3 nodes with MON, MGR, and MDS roles. OSDs will be added later.

My goal is for these 3 nodes to be fully interchangeable, with the ability to administer the cluster from any of them without risk if a node fails.

I have identified that the solution involves synchronizing /var/lib/ceph/ (excluding the bootstrap file) across all nodes.

However:

- Is this the right approach to achieve this goal?

- Which tool should I use for reliable bidirectional synchronization?

- What are the potential risks (conflicts, corruption) and precautions to take?

Have you implemented such a configuration in production before?

Thank you for your advice.