Learning Ceph - Second Edition

Time synchronization

Ceph demands that back-end servers, especially the MONs, have closely synchronized clocks. Ceph warns if the MONs experience greater than 50ms of time skew among themselves, though with modern tools sub-millisecond accuracy is quite achievable. The venerable ntpd time daemon still works, though the newer and legacy-free chrony provides stronger syncing and better accuracy. One can sync against internal corporate time sources including GPS-source appliances or from public servers. It is strongly advised to provision multiple, diverse time sources; the daemons will pool them periodically and select the best to sync against. The more sources one configures, the more tolerant the system is of connectivity glitches and external ...