OSDs are added via a new ceph-osd unit. The unit’s underlying machine is understood to house one or more storage devices.
Ensure that the cluster is in a healthy state. On any MON (unit ceph-mon/1 is just an example) run a status check:
juju ssh ceph-mon/1 sudo ceph status
Add a ceph-osd unit:
juju add-unit ceph-osd
A specific underlying machine (MAAS node) can be chosen via Juju constraints.
If the new unit’s machine has disks that are not listed by the ceph-osd charm’s osd-devices configuration option then the add-disk action should be used to manually add OSD volumes:
juju run-action --wait ceph-osd/5 add-disk osd-devices=/dev/sde
Alternatively, update the value of the osd-devices option:
juju config ceph-osd osd-devices='/dev/sdb /dev/sdc /dev/sde'
An existing OSD cannot be removed from the cluster by mistakenly omitting it from the updated value of option