A storage solution is rated on the basis of its flexibility; a good storage solution should be flexible enough to support its expansion and reduction without causing any downtime to the services. Traditional storage systems are very limited when it comes to flexibility; they do support storage capacity addition, but to a very small extent, and there's no support for online capacity reduction. You are locked with storage capacity and cannot perform changes as per your needs.

Ceph is an absolute, flexible storage system providing online and on-the-fly changes to storage capacity either by expansion or reduction. In the last section, we saw how easy the scale-out operation with Ceph is. We added a new node, ceph-node4, with three OSDs to the Ceph cluster. Now, we will demonstrate the scaling-down operation on a Ceph cluster, without any impact on its accessibility, by removing ceph-node4 out of the Ceph cluster.