NFS

CephFS namespaces can be exported over NFS protocol using the NFS-Ganesha NFS server. This document provides information on configuring NFS-Ganesha clusters manually. The simplest and preferred way of managing NFS-Ganesha clusters and CephFS exports is using ceph nfs ... commands. See CephFS & RGW Exports over NFS for more details. As the deployment is done using cephadm or rook.

Requirements

  • Ceph file system (preferably latest stable luminous or higher versions)

  • In the NFS server host machine, ‘libcephfs2’ (preferably latest stable luminous or higher), ‘nfs-ganesha’ and ‘nfs-ganesha-ceph’ packages (latest ganesha v2.5 stable or higher versions)

  • NFS-Ganesha server host connected to the Ceph public network

Note

It is recommended to use 3.5 or later stable version of NFS-Ganesha packages with pacific (16.2.x) or later stable version of Ceph packages.

Configuring NFS-Ganesha to export CephFS

NFS-Ganesha provides a File System Abstraction Layer (FSAL) to plug in different storage backends. FSAL_CEPH is the plugin FSAL for CephFS. For each NFS-Ganesha export, FSAL_CEPH uses a libcephfs client, user-space CephFS client, to mount the CephFS path that NFS-Ganesha exports.

Setting up NFS-Ganesha with CephFS, involves setting up NFS-Ganesha’s configuration file, and also setting up a Ceph configuration file and cephx access credentials for the Ceph clients created by NFS-Ganesha to access CephFS.

NFS-Ganesha configuration

A sample ganesha.conf configured with FSAL_CEPH can be found here, https://github.com/nfs-ganesha/nfs-ganesha/blob/next/src/config_samples/ceph.conf. It is suitable for a standalone NFS-Ganesha server, or an active/passive configuration of NFS-Ganesha servers managed by some sort of clustering software (e.g., Pacemaker). Important details about the options are added as comments in the sample conf. There are options to do the following:

  • minimize Ganesha caching wherever possible since the libcephfs clients (of FSAL_CEPH) also cache aggressively

  • read from Ganesha config files stored in RADOS objects

  • store client recovery data in RADOS OMAP key-value interface

  • mandate NFSv4.1+ access

  • enable read delegations (need at least v13.0.1 ‘libcephfs2’ package and v2.6.0 stable ‘nfs-ganesha’ and ‘nfs-ganesha-ceph’ packages)

Important

Under certain conditions, NFS access using the CephFS FSAL fails. This causes an error to be thrown that reads “Input/output error”. Under these circumstances, the application metadata must be set for the CephFS metadata and CephFS data pools. Do this by running the following command:

ceph osd pool application set <cephfs_metadata_pool> cephfs <cephfs_data_pool> cephfs

Configuration for libcephfs clients

Required ceph.conf for libcephfs clients includes:

  • a [client] section with mon_host option set to let the clients connect to the Ceph cluster’s monitors, usually generated via ceph config generate-minimal-conf, e.g.,

    [global]
        mon host = [v2:192.168.1.7:3300,v1:192.168.1.7:6789], [v2:192.168.1.8:3300,v1:192.168.1.8:6789], [v2:192.168.1.9:3300,v1:192.168.1.9:6789]

Mount using NFSv4 clients

It is preferred to mount the NFS-Ganesha exports using NFSv4.1+ protocols to get the benefit of sessions.

Conventions for mounting NFS resources are platform-specific. The following conventions work on Linux and some Unix platforms:

mount -t nfs -o nfsvers=4.1,proto=tcp <ganesha-host-name>:<ganesha-pseudo-path> <mount-point>