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Ceph Filesystem (CephFS)

Storage pool type: cephfs

CephFS implements a POSIX-compliant filesystem, using a Ceph storage cluster to store its data. As CephFS builds upon Ceph, it shares most of its properties. This includes redundancy, scalability, self-healing, and high availability.

Tip
 {pve} can manage Ceph setups, which makes configuring a CephFS storage easier. As modern hardware offers a lot of processing power and RAM, running storage services and VMs on same node is possible without a significant performance impact.

To use the CephFS storage plugin, you must replace the stock Debian Ceph client, by adding our Ceph repository. Once added, run apt update, followed by apt dist-upgrade, in order to get the newest packages.

Warning
 Please ensure that there are no other Ceph repositories configured. Otherwise the installation will fail or there will be mixed package versions on the node, leading to unexpected behavior.

Configuration

This backend supports the common storage properties nodes, disable, content, as well as the following cephfs specific properties:

fs-name

Name of the Ceph FS.

monhost

List of monitor daemon addresses. Optional, only needed if Ceph is not running on the {pve} cluster.

path

The local mount point. Optional, defaults to /mnt/pve/<STORAGE_ID>/.

username

Ceph user id. Optional, only needed if Ceph is not running on the {pve} cluster, where it defaults to admin.

subdir

CephFS subdirectory to mount. Optional, defaults to /.

fuse

Access CephFS through FUSE, instead of the kernel client. Optional, defaults to 0.

Configuration example for an external Ceph cluster (/etc/pve/storage.cfg)
cephfs: cephfs-external
        monhost 10.1.1.20 10.1.1.21 10.1.1.22
        path /mnt/pve/cephfs-external
        content backup
        username admin
        fs-name cephfs
Note
 Don’t forget to set up the client’s secret key file, if cephx was not disabled.

Authentication

Note
 If Ceph is installed locally on the {pve} cluster, the following is done automatically when adding the storage.

If you use cephx authentication, which is enabled by default, you need to provide the secret from the external Ceph cluster.

To configure the storage via the CLI, you first need to make the file containing the secret available. One way is to copy the file from the external Ceph cluster directly to one of the {pve} nodes. The following example will copy it to the /root directory of the node on which we run it:

# scp <external cephserver>:/etc/ceph/cephfs.secret /root/cephfs.secret

Then use the pvesm CLI tool to configure the external RBD storage, use the --keyring parameter, which needs to be a path to the secret file that you copied. For example:

# pvesm add cephfs <name> --monhost "10.1.1.20 10.1.1.21 10.1.1.22" --content backup --keyring /root/cephfs.secret

When configuring an external RBD storage via the GUI, you can copy and paste the secret into the appropriate field.

The secret is only the key itself, as opposed to the rbd backend which also contains a [client.userid] section.

The secret will be stored at

# /etc/pve/priv/ceph/<STORAGE_ID>.secret

A secret can be received from the Ceph cluster (as Ceph admin) by issuing the command below, where userid is the client ID that has been configured to access the cluster. For further information on Ceph user management, see the Ceph docs.[cephusermgmt]

# ceph auth get-key client.userid > cephfs.secret

Storage Features

The cephfs backend is a POSIX-compliant filesystem, on top of a Ceph cluster.

Table 1. Storage features for backend cephfs
Content types Image formats Shared Snapshots Clones

vztmpl iso backup snippets

none

yes

yes[1]

no

[1] While no known bugs exist, snapshots are not yet guaranteed to be stable, as they lack sufficient testing.