Use an external Ceph cluster with the Overcloud

Use an external Ceph cluster with the Overcloud

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

This happens 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 Installing the Undercloud.

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

  # 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:

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

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

    ceph::profile::params::rbd_default_features: '1'

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

bash /usr/share/openstack-tripleo-heat-templates/deployed-server/scripts/
for h in $OVERCLOUD_HOSTS ; do
    ssh $h -l stack "sudo groupadd ceph -g 64045 ; sudo useradd ceph -u 64045 -g ceph"

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 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.

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
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