The Manager daemon runs alongside the monitors. It provides an interface to monitor the cluster. Since the release of Ceph luminous, at least one ceph-mgr [15] daemon is required.
Multiple Managers can be installed, but only one Manager is active at any given time.
pveceph mgr create
It is recommended to install the Ceph Manager on the monitor nodes. For high availability install more then one manager.
To remove a Ceph Manager via the GUI, first select a node in the tree view and go to the Ceph → Monitor panel. Select the Manager and click the Destroy button.
To remove a Ceph Monitor via the CLI, first connect to the node on which the Manager is running. Then execute the following command:
pveceph mgr destroy
While a manager is not a hard-dependency, it is crucial for a Ceph cluster, as it handles important features like PG-autoscaling, device health monitoring, telemetry and more.