The management cluster requires minimum three storage devices per node for Ceph:
The first device is always used by the operating system.
At least one disk per server must be configured as a device managed by a Ceph OSD.
One disk per server is required for
LocalVolumeProvisioner for storing data of persistent volumes
served by the Local Storage Static Provisioner
(local-volume-provisioner).
The recommended number of Ceph OSDs per a management cluster node is two or more. Container Cloud supports up to 22 Ceph OSDs per node.