Module 5 - Scaling up a Ceph cluster#

Ceph is designed to scale to exabyte level. Scaling a Ceph cluster is a matter of just adding nodes and Ceph will take care of the rest. In this module we will add a new OSD node osd-node4 with 3 drives to our existing Ceph cluster of 3 OSD nodes.

• We currently have 3 OSD Ceph cluster with total 9 OSDs, lets verify it again

$ ceph osd stat
$ ceph osd tree

Once the new node osd-node4 is added we will then have 4 Node Ceph cluster with 12 disks altogether.

• To scale up Ceph cluster, login to the mgmt node which is our ceph-ansible node

• Edit /etc/ansible/hosts file

$ sudo vi /etc/ansible/hosts

• Add osd-node4 under [osds] section. Save and exit from editor

[mons]
mon-node1
mon-node2
mon-node3
[osds]
osd-node1
osd-node2
osd-node3
osd-node4
[rgws]
rgw-node1

• Navigate to the Ansible configuration directory /usr/share/ceph-ansible/

$ cd /usr/share/ceph-ansible/

• Now run Ansible playbook, which will make sure the osd-node4 is added to existing Ceph cluster

$ ansible-playbook site.yml -u ceph

• Once Ansible run is completed, make sure there is no failed item under PLAY RECAP
• So ceph-ansible has scaled up our Ceph cluster, lets verify it

$ ceph osd stat
$ ceph osd tree
$ ceph -s

We have reached the end of Module-5. At this point we have scaled up our Ceph cluster to 4 OSD node, without any downtime or service breaks. This shows, how seamless is Ceph scale up operation