So, the reason I think an action is better than juju run:
1) the charm knows which OSDs are on which node; I, as a human,
don't. That makes at least two of the things jjo mentioned a
multi-step process, which is better wrapped in an action
2) putting it into an action means it can be tested and become part
of the normal CI/QA process and won't break if (for example) ceph
change their CLI
So, the reason I think an action is better than juju run:
1) the charm knows which OSDs are on which node; I, as a human,
don't. That makes at least two of the things jjo mentioned a
multi-step process, which is better wrapped in an action
2) putting it into an action means it can be tested and become part
of the normal CI/QA process and won't break if (for example) ceph
change their CLI