Use an external Ceph cluster with the Overcloud

TripleO supports use of an external Ceph cluster for certain services deployed in the Overcloud.

Deploying Cinder, Glance, Nova, Gnocchi with an external Ceph RBD service

The overcloud may be configured to use an external Ceph RBD service by enabling a particular environment file when deploying the Overcloud. For Ocata and earlier use environments/puppet-ceph-external.yaml. For Pike and newer, use environments/ceph-ansible/ceph-ansible-external.yaml and install ceph-ansible on the Undercloud as described in TripleO OpenStack Deployment. For Pike and newer a Ceph container is downloaded and executed on Overcloud nodes to use Ceph binaries only available within the container. These binaries are used to create the CephX client keyrings on the overcloud. Thus it is necessary when preparing to deploy a containerized overcloud, as described in Container Image Preparation, to include the Ceph container even if that overcloud will only connect to an external Ceph cluster.

Some of the parameters in the above environment files can be overridden:

parameter_defaults:
  # Enable use of RBD backend in nova-compute
  NovaEnableRbdBackend: true
  # Enable use of RBD backend in cinder-volume
  CinderEnableRbdBackend: true
  # Backend to use for cinder-backup
  CinderBackupBackend: ceph
  # Backend to use for glance
  GlanceBackend: rbd
  # Backend to use for gnocchi-metricsd
  GnocchiBackend: rbd
  # Name of the Ceph pool hosting Nova ephemeral images
  NovaRbdPoolName: vms
  # Name of the Ceph pool hosting Cinder volumes
  CinderRbdPoolName: volumes
  # Name of the Ceph pool hosting Cinder backups
  CinderBackupRbdPoolName: backups
  # Name of the Ceph pool hosting Glance images
  GlanceRbdPoolName: images
  # Name of the Ceph pool hosting Gnocchi metrics
  GnocchiRbdPoolName: metrics
  # Name of the user to authenticate with the external Ceph cluster
  CephClientUserName: openstack

The pools and the CephX user must be created on the external Ceph cluster before deploying the Overcloud. TripleO expects a single user, configured via CephClientUserName, to have the capabilities to use all the OpenStack pools; the user could be created with a command like this:

ceph auth add client.openstack mon 'allow r' osd 'allow class-read object_prefix rbd_children, allow rwx pool=volumes, allow rwx pool=vms, allow rwx pool=images, allow rwx pool=backups, allow rwx pool=metrics'

In addition to the above customizations, the deployer needs to provide at least three required parameters related to the external Ceph cluster:

parameter_defaults:
  # The cluster FSID
  CephClusterFSID: '4b5c8c0a-ff60-454b-a1b4-9747aa737d19'
  # The CephX user auth key
  CephClientKey: 'AQDLOh1VgEp6FRAAFzT7Zw+Y9V6JJExQAsRnRQ=='
  # The list of Ceph monitors
  CephExternalMonHost: '172.16.1.7, 172.16.1.8, 172.16.1.9'

The above parameters will result in TripleO creating a Ceph configuration file and cephx keyring in /etc/ceph on every node which needs to connect to Ceph to use the RBD service.

Configuring Ceph Clients for Multiple External Ceph RBD Services

In Train and newer it’s possible to use TripleO to deploy an overcloud which is capable of using the RBD services of multiple external Ceph clusters. A separate keyring and Ceph configuration file is created for each external Ceph cluster in /etc/ceph on every overcloud node which needs to connect to Ceph. This functionality is provided by the CephExternalMultiConfig parameter.

Do not use CephExternalMultiConfig when configuring an overcloud to use only one external Ceph cluster. Instead follow the example in the previous section. The example in the previous section and the method of deploying an internal Ceph cluster documented in Configuring Ceph with Custom Config Settings are mutually exclusive per Heat stack. The following scenarios are the only supported ones in which CephExternalMultiConfig may be used per Heat stack:

  • One external Ceph cluster configured, as described in previous section, in addition to multiple external Ceph clusters configured via CephExternalMultiConfig.

  • One internal Ceph cluster, as described in Configuring Ceph with Custom Config Settings in addition to multiple external ceph clusters configured via CephExternalMultiConfig.

The CephExternalMultiConfig parameter is used like this:

CephExternalMultiConfig:
  - cluster: 'ceph2'
    fsid: 'af25554b-42f6-4d2b-9b9b-d08a1132d3e8'
    external_cluster_mon_ips: '172.18.0.5,172.18.0.6,172.18.0.7'
    keys:
      - name: "client.openstack"
        caps:
          mgr: "allow *"
          mon: "profile rbd"
          osd: "osd: profile rbd pool=volumes, profile rbd pool=backups, profile rbd pool=vms, profile rbd pool=images"
        key: "AQCwmeRcAAAAABAA6SQU/bGqFjlfLro5KxrB1Q=="
        mode: "0600"
    dashboard_enabled: false
  - cluster: 'ceph3'
    fsid: 'e2cba068-5f14-4b0f-b047-acf375c0004a'
    external_cluster_mon_ips: '172.18.0.8,172.18.0.9,172.18.0.10'
    keys:
      - name: "client.openstack"
        caps:
          mgr: "allow *"
          mon: "profile rbd"
          osd: "osd: profile rbd pool=volumes, profile rbd pool=backups, profile rbd pool=vms, profile rbd pool=images"
        key: "AQCwmeRcAAAAABAA6SQU/bGqFjlfLro5KxrB2Q=="
        mode: "0600"
    dashboard_enabled: false

The above, in addition to the parameters from the previous section, will result in an overcloud with the following files in /etc/ceph:

  • ceph.client.openstack.keyring

  • ceph.conf

  • ceph2.client.openstack.keyring

  • ceph2.conf

  • ceph3.client.openstack.keyring

  • ceph3.conf

The first two files which start with ceph will be created based on the parameters discussed in the previous section. The next two files which start with ceph2 will be created based on the parameters from the first list item within the CephExternalMultiConfig parameter (e.g. cluster: ceph2). The last two files which start with ceph3 will be created based on the parameters from the last list item within the CephExternalMultiConfig parameter (e.g. cluster: ceph3).

The last four files in the list which start with ceph2 or ceph3 will also contain parameters found in the first two files which start with ceph except where those parameters intersect. When there’s an intersection those parameters will be overridden with the values from the CephExternalMultiConfig parameter. For example there will only be one FSID in each Ceph configuration file with the following values per file:

  • ceph.conf will have fsid = 4b5c8c0a-ff60-454b-a1b4-9747aa737d19 (as seen in the previous section)

  • ceph2.conf will have fsid = af25554b-42f6-4d2b-9b9b-d08a1132d3e8

  • ceph3.conf will have fsid = e2cba068-5f14-4b0f-b047-acf375c0004a

However, if the external_cluster_mon_ips key was not set within the CephExternalMultiConfig parameter, then all three Ceph configuration files would contain mon host = 172.16.1.7, 172.16.1.8, 172.16.1.9, as seen in the previous section. Thus, it is necessary to override the external_cluster_mon_ips key within each list item of the CephExternalMultiConfig parameter because each external Ceph cluster will have its own set of unique monitor IPs.

The CephExternalMultiConfig and external_cluster_mon_ips keys map one to one but have different names because each element of the CephExternalMultiConfig list should contain a map of keys and values directly supported by ceph-ansible. See ceph-ansible/group_vars for an example of all possible keys.

The following parameters are the minimum necessary to configure an overcloud to connect to an external ceph cluster:

  • cluster: The name of the configuration file and key name prefix. This name defaults to “ceph” so if this parameter is not overridden there will be a name collision. It is not relevant if the external ceph cluster’s name is already “ceph”. For client role configuration this parameter is only used for setting a unique name for the configuration and key files.

  • fsid: The FSID of the external ceph cluster.

  • external_cluster_mon_ips: The list of monitor IPs of the external ceph cluster as a single string where each IP is comma delimited. If the external Ceph cluster is using both the v1 and v2 MSGR protocol this value may look like ‘[v2:10.0.0.1:3300, v1:10.0.0.1:6789], [v2:10.0.0.2:3300, v1:10.0.0.2:6789], [v2:10.0.0.3:3300, v1:10.0.0.3:6789]’.

  • dashboard_enabled: Always set this value to false when using CephExternalMultiConfig. It ensures that the Ceph Dashboard is not installed. It is not supported to use ceph-ansible dashboard roles to communicate with an external Ceph cluster so not passing this parameter with a value of false within CephExternalMultiConfig will result in a failed deployment because the default value of true will be used.

  • keys: This is a list of maps where each map defines CephX keys which OpenStack clients will use to connect to an external Ceph cluster. As stated in the previous section, the pools and the CephX user must be created on the external Ceph cluster before deploying the overcloud. The format of each map is the same as found in ceph-ansible. Thus, if the external Ceph cluster was deployed by ceph-ansible, then the deployer of that cluster could share that map with the TripleO deployer so that it could be used as a list item of CephExternalMultiConfig. Similarly, the CephExtraKeys parameter, described in the Configuring Ceph with Custom Config Settings documentation, has the same syntax.

Deploying Manila with an External CephFS Service

If chosing to configure Manila with Ganesha as NFS gateway for CephFS, with an external Ceph cluster, then add environments/manila-cephfsganesha-config.yaml to the list of environment files used to deploy the overcloud and also configure the following parameters:

parameter_defaults:
  ManilaCephFSDataPoolName: manila_data
  ManilaCephFSMetadataPoolName: manila_metadata
  ManilaCephFSCephFSAuthId: 'manila'
  CephManilaClientKey: 'AQDLOh1VgEp6FRAAFzT7Zw+Y9V6JJExQAsRnRQ=='

Which represent the data and metadata pools in use by the MDS for the CephFS filesystems, the CephX keyring to use and its secret.

Like for the other services, the pools and keyring must be created on the external Ceph cluster before attempting the deployment of the overcloud. The keyring should look like the following:

ceph auth add client.manila mgr "allow *" mon "allow r, allow command 'auth del', allow command 'auth caps', allow command 'auth get', allow command 'auth get-or-create'" mds "allow *" osd "allow rw"

Compatibility Options

As of the Train release TripleO will install Ceph Nautilus. If the external Ceph cluster uses the Hammer release instead, pass the following parameters to enable backward compatibility features:

parameter_defaults:
  ExtraConfig:
    ceph::profile::params::rbd_default_features: '1'

Configuring Already Deployed Servers to use External Ceph

When using ceph-ansible and Using Already Deployed Servers, it is necessary to run commands like the following from the undercloud before deployment:

export OVERCLOUD_HOSTS="192.168.1.8 192.168.1.42"
bash /usr/share/openstack-tripleo-heat-templates/deployed-server/scripts/enable-ssh-admin.sh
for h in $OVERCLOUD_HOSTS ; do
    ssh $h -l stack "sudo groupadd ceph -g 64045 ; sudo useradd ceph -u 64045 -g ceph"
done

In the example above, the OVERCLOUD_HOSTS variable should be set to the IPs of the overcloud hosts which will be Ceph clients (e.g. Nova, Cinder, Glance, Gnocchi, Manila, etc.). The enable-ssh-admin.sh script configures a user on the overcloud nodes that Ansible uses to configure Ceph. The for loop creates the Ceph user on the relevant overcloud hosts.

Note

If the overcloud is named differently than the default (“overcloud”), then you’ll have to set the OVERCLOUD_PLAN variable as well

Deployment of an Overcloud with External Ceph

Finally add the above environment files to the deploy commandline. For Ocata and earlier:

openstack overcloud deploy --templates -e /usr/share/openstack-tripleo-heat-templates/environments/puppet-ceph-external.yaml -e ~/my-additional-ceph-settings.yaml

For Pike and later:

openstack overcloud deploy --templates -e /usr/share/openstack-tripleo-heat-templates/environments/ceph-ansible/ceph-ansible-external.yaml -e ~/my-additional-ceph-settings.yaml