As Ceph OSDs are tightly coupled to underlying storage, in almost any production-scale system they rate dedicated servers. This approach allows scaling up and out at will, along with a degree of rolling or ad-hoc maintenance flexibility that will turn your Compute and Network colleagues green with envy.
Ceph Monitor (MON) services have very different needs. They typically do not demand much in the way of CPU, and their RAM requirements are not considerable by modern standards. MONs do not require considerable local storage capacity either but they need it to be durable. As we described in Chapter 3, Hardware and Network Selection, SSDs used for Ceph Monitor DBs receive steady traffic. MON DBs in larger clusters ...
