Check cluster status,

ceph -s
#ceph health
#ceph status

Check the cluster logs in real time,

ceph -w

Stop/Start or restart the whole thing on a node or admin,

#systemctl stop
#systemctl start
#systemctl restart

Review the disk/osd tree,

ceph osd tree

Check the OSD usage!

ceph osd stat

Check the Metadata services,

ceph mds stat