Chapter 1. The Shared File Systems service with native CephFS

CephFS is the highly scalable, open-source, distributed file system component of Ceph, a unified distributed storage platform. Ceph Storage implements object, block, and file storage using Reliable Autonomic Distributed Object Store (RADOS). CephFS, which is POSIX compatible, provides file access to a Ceph Storage cluster.

The Shared File Systems service enables users to create shares in CephFS and access them using the native Ceph File System protocol. The Shared File Systems service manages the life cycle of these shares from within OpenStack.

With this release, director can deploy the Shared File Systems with a native CephFS back end on the overcloud.


This document pertains to the deployment and use of native CephFS to provide self-service Shared File Systems service (manila) in your Red Hat OpenStack Platform Cloud through the native CephFS NAS protocol. This type of deployment requires guest VM access to Ceph public network and infrastructure. Deploy native CephFS with trusted OpenStack Platform tenants only, because it requires a permissive trust model that is not suitable for general purpose OpenStack Platform deployments.


For general purpose OpenStack Platform deployments that use a conventional tenant trust model, you can deploy CephFS through the NFS protocol. For more information about trust models, see Native CephFS back end security. For more information about using CephFS through NFS, see Deploying the Shared File Systems service with CephFS through NFS.

1.1. CephFS with native driver

The CephFS native driver combines the OpenStack Shared File Systems service (manila) and Red Hat Ceph Storage. When you use Red Hat OpenStack (RHOSP) director, the Controller nodes host the Ceph daemons, such as the manager, metadata servers (MDS), and monitors (MON) and the Shared File Systems services.

Compute nodes can host one or more projects. Projects, which were formerly referred to as tenants, are represented in the following graphic by the white boxes. Projects contain user-managed VMs, which are represented by gray boxes with two NICs. To access the ceph and manila daemons projects, connect to the daemons over the public Ceph storage network.

On this network, you can access data on the storage nodes provided by the Ceph Object Storage Daemons (OSDs). Instances, or virtual machines (VMs), that are hosted on the project boot with two NICs: one dedicated to the storage provider network and the second to project-owned routers to the external provider network.

The storage provider network connects the VMs that run on the projects to the public Ceph storage network. The Ceph public network provides back end access to the Ceph object storage nodes, metadata servers (MDS), and Controller nodes.

Using the native driver, CephFS relies on cooperation with the clients and servers to enforce quotas, guarantee project isolation, and for security. CephFS with the native driver works well in an environment with trusted end users on a private cloud. This configuration requires software that is running under user control to cooperate and work correctly.

cephfs nfs topology native driver

1.2. Native CephFS back end security

The native CephFS back end requires a permissive trust model for Red Hat OpenStack Platform (RHOSP) tenants. This trust model is not appropriate for general purpose OpenStack Platform clouds that deliberately block users from directly accessing the infrastructure behind the services that the OpenStack Platform provides.

With native CephFS, user Compute instances connect directly to the Ceph public network where the Ceph service daemons are exposed. CephFS clients that run on user VMs interact cooperatively with the Ceph service daemons, and they interact directly with RADOS to read and write file data blocks.

CephFS quotas, which enforce Shared File Systems (manila) share sizes, are enforced on the client side, such as on VMs that are owned by Red Hat OpenStack Platform (RHOSP) users. The client side software on user VMs might not be current, which can leave critical cloud infrastructure vulnerable to malicious or inadvertently harmful software that targets the Ceph service ports.

Deploy native CephFS as a back end only in environments in which trusted users keep client-side software up to date. Ensure that no software that can impact the Ceph Storage infrastructure runs on your VMs.

For a general purpose Red Hat OpenStack Platform (RHOSP) deployment that serves many untrusted users, deploy CephFS through NFS. For more information about using CephFS through NFS, see Deploying the Shared File Systems service with CephFS through NFS.

Users might not keep client-side software current, and they might fail to exclude harmful software from their VMs, but using CephFS through NFS, they only have access to the public side of an NFS server, not to the Ceph infrastructure itself. NFS does not require the same kind of cooperative client and, in the worst case, an attack from a user VM can damage the NFS gateway without damaging the Ceph storage infrastructure behind it.

You can expose the native CephFS back end to all trusted users, but you must enact the following security measures:

  • Configure the storage network as a provider network.
  • Impose role-based access control (RBAC) policies to secure the Storage provider network.
  • Create a private share type.