Chapter 1. CPU

Ceph OSDs run the storage cluster service, calculate data placement with CRUSH, replicate data, and maintain their own copy of the cluster map. Ceph OSDs that host erasure-coded pools will use more CPU than Ceph OSDs that host replicated pools. Therefore, OSDs should have a reasonable amount of processing power and should consider the storage strategy(ies) you intend to use. Monitors simply maintain a master copy of the cluster map, so they are not CPU intensive.

You must also consider whether the host machine will run CPU-intensive processes in addition to Ceph daemons. For example, if your hosts will run computing VMs (e.g., OpenStack Nova), you will need to ensure that these other processes leave sufficient processing power for Ceph daemons. We recommend running additional CPU-intensive processes on separate hosts.