Mastering Proxmox - Third Edition

Metadata server

A metadata server (MDS) stores meta information for the Ceph FileSystem or CephFS. The Ceph block and object storage do not use MDS. So in a cluster, if block and object are the only types that are going to be used, it will not be necessary to set up an MDS server. Like a monitor, MDS needs to be set up on a different machine of its own to achieve high performance. As of Proxmox version 5.0, MDS cannot be managed or created from the Proxmox GUI.

The CephFS is not fully standardized yet and is still in the development phase. It should not be used to store mission-critical data. It is mostly stable, but unforeseen bugs may still cause major issues, such as data loss. Note that there have not been many reports of mass data loss ...