Distributed Multibackend Storage

In Ussuri and newer, TripleO is able to extend Distributed Compute Node deployment to include distributed image management and persistent storage with the benefits of using OpenStack and Ceph.

Features

This Distributed Multibackend Storage design extends the architecture described in Distributed Compute Node deployment to support the following worklow.

  • Upload an image to the Central site using glance image-create command with –file and –store default_backend parameters.

  • Move a copy of the same image to DCN sites using a command like glance image-import <IMAGE-ID> –stores dcn1,dcn2 –import-method copy-image.

  • The image’s unique ID will be shared consistently across sites

  • The image may be copy-on-write booted on any DCN site as the RBD pools for Glance and Nova will use the same local Ceph cluster.

  • If the Glance server at each DCN site was configured with write access to the Central Ceph cluster as an additional store, then an image generated from making a snapshot of an instance running at a DCN site may be copied back to the central site and then copied to additional DCN sites.

  • The same Ceph cluster per site may also be used by Cinder as an RBD store to offer local volumes in active/active mode.

In the above workflow the only time RBD traffic crosses the WAN is when an image is imported or copied between sites. Otherwise all RBD traffic is local to each site for fast COW boots, and performant IO to the local Cinder and Nova Ceph pools.

Architecture

The architecture to support the above features has the following properties.

  • A separate Ceph cluster at each availability zone or geographic location

  • Glance servers at each availability zone or geographic location

  • The containers implementing the Ceph clusters may be collocated on the same hardware providing compute services, i.e. the compute nodes may be hyper-converged, though it is not necessary that they be hyper-converged

  • It is not necessary to deploy Glance and Ceph at each DCN site, if storage services are not needed at that DCN site

In this scenario the Glance service at the central site is configured with multiple stores such that.

  • The central Glance server’s default store is the central Ceph cluster using the RBD driver

  • The central Glance server has additional RBD stores; one per DCN site running Ceph

Similarly the Glance server at each DCN site is configured with multiple stores such that.

  • Each DCN Glance server’s default store is the DCN Ceph cluster that is in the same geographic location.

  • Each DCN Glance server is configured with one additional store which is the Central RBD Ceph cluster.

Though there are Glance services distributed to multiple sites, the Glance client for overcloud users should use the public Glance endpoints at the central site. These endpoints may be determined by querying the Keystone service, which only runs at the central site, with openstack endpoint list. Ideally all images should reside in the central Glance and be copied to DCN sites before instances of those images are booted on DCN sites. If an image is not copied to a DCN site before it is booted, then the image will be streamed to the DCN site and then the image will boot as an instance. This happens because Glance at the DCN site has access to the images store at the Central ceph cluster. Though the booting of the image will take time because it has not been copied in advance, this is still preferable to failing to boot the image.

Stacks

In the example deployment three stacks are deployed:

control-plane

All control plane services including Glance. Includes a Ceph cluster named central which is hypercoverged with compute nodes and runs Cinder in active/passive mode managed by pacemaker.

dcn0

Runs Compute, Glance and Ceph services. The Cinder volume service is configured in active/active mode and not managed by pacemaker. The Compute and Cinder services are deployed in a separate availability zone and may also be in a separate geographic location.

dcn1

Deploys the same services as dcn0 but in a different availability zone and also in a separate geographic location.

Note how the above differs from the Distributed Compute Node deployment example which splits services at the primary location into two stacks called control-plane and central. This example combines the two into one stack.

During the deployment steps all templates used to deploy the control-plane stack will be kept on the undercloud in /home/stack/control-plane, all templates used to deploy the dcn0 stack will be kept on the undercloud in /home/stack/dcn0 and dcn1 will follow the same pattern as dcn0. The sites dcn2, dcn3 and so on may be created, based on need, by following the same pattern.

Ceph Deployment Types

TripleO supports two types of Ceph deployments. An “internal” Ceph deployment is one where a Ceph cluster is deployed as part of the overcloud as described in Configuring Ceph with Custom Config Settings. An “external” Ceph deployment is one where a Ceph cluster already exists and an overcloud is configured to be a client of that Ceph cluster as described in Use an external Ceph cluster with the Overcloud. Ceph external deployments have special meaning to TripleO in the following ways:

  • The Ceph cluster was not deployed by TripleO

  • The OpenStack Ceph client is configured by TripleO

The deployment example in this document uses the “external” term to focus on the second of the above because the client configuration is important. This example differs from the first of the above because Ceph was deployed by TripleO, however relative to other stacks, it is an external Ceph cluster because, for the stacks which configure the Ceph clients, it doesn’t matter that the Ceph server came from a different stack. In this sense, the example in this document uses both types of deployments as described in the following sequence:

  • The central site deploys an internal Ceph cluster called central with an additional cephx keyring which may be used to access the central ceph pools.

  • The dcn0 site deploys an internal Ceph cluster called dcn0 with an additional cephx keyring which may be used to access the dcn0 Ceph pools. During the same deployment the dcn0 site is also configured with the cephx keyring from the previous step so that it is also a client of the external Ceph cluster, relative to dcn0, called central from the previous step. The GlanceMultistoreConfig parameter is also used during this step so that Glance will use the dcn0 Ceph cluster as an RBD store by default but it will also be configured to use the central Ceph cluster as an additional RBD backend.

  • The dcn1 site is deployed the same way as the dcn0 site and the pattern may be continued for as many DCN sites as necessary.

  • The central site is then updated so that in addition to having an internal Ceph deployment for the cluster called central, it is also configured with multiple external ceph clusters, relative to the central site, for each DCN site. This is accomplished by passing the cephx keys which were created during each DCN site deployment as input to the stack update. During the stack update the GlanceMultistoreConfig parameter is added so that Glance will continue to use the central Ceph cluster as an RBD store by default but it will also be configured to use each DCN Ceph cluster as an additional RBD backend.

The above sequence is possible by using the CephExtraKeys parameter as described in Configuring Ceph with Custom Config Settings and the CephExternalMultiConfig parameter described in Use an external Ceph cluster with the Overcloud.

Deployment Steps

This section shows the deployment commands and associated environment files of an example DCN deployment with distributed image management. It is based on the Distributed Compute Node deployment example and does not cover redundant aspects of it such as networking.

Create extra Ceph key

Create /home/stack/control-plane/ceph_keys.yaml with contents like the following:

parameter_defaults:
  CephExtraKeys:
      - name: "client.external"
        caps:
          mgr: "allow *"
          mon: "profile rbd"
          osd: "profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images"
        key: "AQD29WteAAAAABAAphgOjFD7nyjdYe8Lz0mQ5Q=="
        mode: "0600"

The key should be considered sensitive and may be randomly generated with the following command:

python3 -c 'import os,struct,time,base64; key = os.urandom(16); header = struct.pack("<hiih", 1, int(time.time()), 0, len(key)) ; print(base64.b64encode(header + key).decode())'

Passing CephExtraKeys, as above, during deployment will result in a Ceph cluster with pools which may be accessed by the cephx user “client.external”. The same parameters will be used later when the DCN overclouds are configured as external Ceph clusters. For more information on the CephExtraKeys parameter see the document Configuring Ceph with Custom Config Settings section called Configuring CephX Keys.

Create control-plane roles

Generate the roles used for the deployment:

openstack overcloud roles generate Controller ComputeHCI -o ~/control-plane/control_plane_roles.yaml

To determine the number of nodes per role create ~/control-plane/roles-counts.yaml with the following:

parameter_defaults:
  ControllerCount: 3
  ComputeHCICount: 3

If you do not wish to hyper-converge the compute nodes with Ceph OSD services, then substitute CephStorage for ComputeHCI and increment the number of Compute nodes. There should at least three Controller nodes and at least three CephStorage or ComputeHCI nodes in order to have a redundant Ceph cluster.

Deploy the control-plane stack

Deploy the control-plane stack:

openstack overcloud deploy \
       --stack control-plane \
       --templates /usr/share/openstack-tripleo-heat-templates/ \
       -r ~/control-plane/control_plane_roles.yaml \
       -n ~/network-data.yaml \
       -e /usr/share/openstack-tripleo-heat-templates/environments/net-multiple-nics.yaml \
       -e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml \
       -e /usr/share/openstack-tripleo-heat-templates/environments/network-environment.yaml \
       -e /usr/share/openstack-tripleo-heat-templates/environments/disable-telemetry.yaml \
       -e /usr/share/openstack-tripleo-heat-templates/environments/podman.yaml \
       -e /usr/share/openstack-tripleo-heat-templates/environments/disable-swift.yaml \
       -e /usr/share/openstack-tripleo-heat-templates/environments/ceph-ansible/ceph-ansible.yaml \
       -e ~/control-plane/role-counts.yaml \
       -e ~/control-plane/ceph.yaml \
       -e ~/control-plane/ceph_keys.yaml

The network related files are included to make the example complete but are not displayed in this document. For more information on configuring networks with distributed compute nodes see Distributed Compute Node deployment.

The environments/ceph-ansible/ceph-ansible.yaml results in ceph-ansible deploying Ceph as part of the control-plane stack. This file also contains both NovaEnableRbdBackend: true and GlanceBackend: rbd. When both of these settings are used, the Glance image_import_plugins setting will contain image_conversion. With this setting enabled commands like glance image-create-via-import with –disk-format qcow2 will result in the image being converted into a raw format, which is optimal for the Ceph RBD driver. If you need to disable image conversion you may override the GlanceImageImportPlugin parameter. For example:

parameter_defaults:
  GlanceImageImportPlugin: []

The ceph.yaml file contains the following which sets the name of the Ceph cluster to “central”:

parameter_defaults:
  CephClusterName: central

The ceph.yaml file should also contain additional parameters like CephAnsibleDisksConfig, CephPoolDefaultSize, CephPoolDefaultPgNum to configure the Ceph cluster relative to the available hardware as described in Configuring Ceph with Custom Config Settings.

The environments/disable-swift.yaml file was passed to disable Swift simply because an object storage system is not needed for this example. However, if an object storage system is desired at the Central site, substitute environments/ceph-ansible/ceph-rgw.yaml in its place to configure Ceph RGW.

The environments/cinder-backup.yaml file is not used in this deployment. It’s possible to enable the Cinder-backup service by using this file but it will only write to the backups pool of the central Ceph cluster.

The ~/control-plane/ceph_keys.yaml and ~/control-plane/role-counts.yaml files were created in the previous sections.

Extract overcloud control-plane and Ceph configuration

Use the openstack overcloud export command to create ~/control-plane-export.yaml as described in Distributed Compute Node deployment:

openstack overcloud export \
        --config-download-dir /var/lib/mistral/control-plane/ \
        --stack control-plane \
        --output-file ~/control-plane-export.yaml

In the above example –config-download-dir may be at a different location if you deployed with a manual config-download as described in TripleO config-download User’s Guide: Deploying with Ansible.

Create ~/central_ceph_external.yaml with content like the following:

parameter_defaults:
  CephExternalMultiConfig:
    - cluster: "central"
      fsid: "3161a3b4-e5ff-42a0-9f53-860403b29a33"
      external_cluster_mon_ips: "172.16.11.84, 172.16.11.87, 172.16.11.92"
      keys:
        - name: "client.external"
          caps:
            mgr: "allow *"
            mon: "profile rbd"
            osd: "profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images"
          key: "AQD29WteAAAAABAAphgOjFD7nyjdYe8Lz0mQ5Q=="
          mode: "0600"
      dashboard_enabled: false
      ceph_conf_overrides:
        client:
          keyring: /etc/ceph/central.client.external.keyring

The CephExternalMultiConfig section of the above is used to configure any DCN node as a Ceph client of the central Ceph cluster. All of the values, except external_cluster_mon_ips, for this section may be obtained from the directory specified by –config-download-dir when the openstack overcloud export command was run. Based on the example provided in this document, the relevant file with the desired values is /var/lib/mistral/control-plane/ceph-ansible/group_vars/all.yml.

For example, the fsid and cluster (name) may be found like this:

cd /var/lib/mistral/control-plane/ceph-ansible/group_vars/
grep fsid: all.yml
grep name: all.yml

The keys section should contain the same list item that was passed to the CephExtraKeys parameter in the first step of this procedure. The key value may also be obtained by looking at the key used by the client.external name in the openstack_keys list found in all.yml. For example, all.yml should contain something which looks like the following and the second item in the list should be used to get the value because it has name set to client.external:

openstack_keys:
-   caps:
      mgr: allow *
      mon: profile rbd
      osd: profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images
    key: AQDIl2teAAAAABAAtFuRHdcS8v3+kk9Y6RzehA==
    mode: '0600'
    name: client.openstack
-   caps:
      mgr: allow *
      mon: profile rbd
      osd: profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images
    key: AQD29WteAAAAABAAphgOjFD7nyjdYe8Lz0mQ5Q==
    mode: '0600'
    name: client.external

To determine the value for external_cluster_mon_ips to provide within the CephExternalMultiConfig parameter, use the inventory generated by config-download and select the storage IP or storage hostname of every node which runs the CephMons service. Based on the example provided in this document, the relevant inventory file is /var/lib/mistral/control-plane/inventory.yaml. For example the nodes in the Controller role run the CephMon service by default on IPs in the storage network so the IPs will be in a section which looks like this:

Controller:
  hosts:
    control-plane-controller-0:
      ansible_host: 192.168.24.16
      ...
      storage_hostname: control-plane-controller-0.storage.localdomain
      storage_ip: 172.16.11.84
      ...
    control-plane-controller-1:
      ansible_host: 192.168.24.22
      ...
      storage_hostname: control-plane-controller-1.storage.localdomain
      storage_ip: 172.16.11.87
      ...

The storage_ip from each host should be combined in a comma delimited list. In this example the parameter is set to external_cluster_mon_ips: “172.16.11.84, 172.16.11.87, 172.16.11.92”. If necessary, the inventory may be regenerated by running the tripleo-ansible-inventory command as described in TripleO config-download User’s Guide: Deploying with Ansible.

The ceph_conf_overrides section should look like the following:

ceph_conf_overrides:
  client:
    keyring: /etc/ceph/central.client.external.keyring

The above will result in the following lines in /etc/ceph/central.conf on all DCN nodes which interact with the central Ceph cluster:

[client]
keyring = /etc/ceph/central.client.external.keyring

The name of the external Ceph cluster, relative to the DCN nodes, is central so the relevant Ceph configuration file is called /etc/ceph/central.conf. Optionally, the path to the key may be confirmed by looking directly on any node running the CephMon service on the control-plane stack if desired. If the conventions in this document are followed, then it should remain consistent. This directive is necessary so that the Glance service on all DCN nodes, which will be deployed in the next section, knows which keyring to use when connecting to the central Ceph cluster.

It is necessary to always pass dashboard_enabled: false when using CephExternalMultiConfig as the Ceph dashboard cannot be deployed when configuring an overcloud as a client of an external Ceph cluster.

For more information on the CephExternalMultiConfig parameter see Use an external Ceph cluster with the Overcloud.

Create extra Ceph key for dcn0

Create ~/dcn0/ceph_keys.yaml with content like the following:

parameter_defaults:
  CephExtraKeys:
    - name: "client.external"
      caps:
        mgr: "allow *"
        mon: "profile rbd"
        osd: "profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images"
      key: "AQBO/mteAAAAABAAc4mVMTpq7OFtrPlRFqN+FQ=="
      mode: "0600"

The CephExtraKeys section of the above should follow the same pattern as the first step of this procedure. It should use a new key, which should be considered sensitive and can be randomly generated with the same Python command from the first step. This same key will be used later when Glance on the central site needs to connect to dcn0 “images”.

Override Glance defaults for dcn0

Create ~/dcn0/glance.yaml with content like the following:

parameter_defaults:
  GlanceShowMultipleLocations: true
  GlanceEnabledImportMethods: web-download,copy-image
  GlanceBackend: rbd
  GlanceStoreDescription: 'dcn0 rbd glance store'
  GlanceMultistoreConfig:
    central:
      GlanceBackend: rbd
      GlanceStoreDescription: 'central rbd glance store'
      CephClientUserName: 'external'
      CephClusterName: central

The GlanceEnabledImportMethods parameter is used to override the default of ‘web-download’ to also include ‘copy-image’, which is necessary to support the workflow described earlier.

By default Glance on the dcn0 node will use the RBD store of the dcn0 Ceph cluster. The GlanceMultistoreConfig parameter is then used to add an additional store of type RBD called central which uses the Ceph cluster deployed by the control-plane stack so the CephClusterName is set to “central”. The CephClientUserName is set to “external” because the additional key which was passed with CephExtraKeys to the control-plane stack had a name of “client.external”.

Create DCN roles for dcn0

Generate the roles used for the deployment:

openstack overcloud roles generate DistributedComputeHCI DistributedComputeHCIScaleOut -o ~/dcn0/dcn_roles.yaml

The DistributedComputeHCI role includes the default compute services, the cinder volume service, and also includes the Ceph Mon, Mgr, and OSD services for deploying a Ceph cluster at the distributed site. Using this role, both the compute services and Ceph services are deployed on the same nodes, enabling a hyper-converged infrastructure for persistent storage at the distributed site. When Ceph is used, there must be a minimum of three DistributedComputeHCI nodes. This role also includes a Glance server, provided by the GlanceApiEdge service with in the DistributedComputeHCI role. The Nova compute service of each node in the DistributedComputeHCI role is configured by default to use its local Glance server.

DistributedComputeHCIScaleOut role is like the DistributedComputeHCI role but does not run the Ceph Mon and Mgr service. It offers the Ceph OSD service however, so it may be used to scale up storage and compute services at each DCN site after the minimum of three DistributedComputeHCI nodes have been deployed. There is no GlanceApiEdge service in the DistributedComputeHCIScaleOut role but in its place the Nova compute service of the role is configured by default to connect to a local HaProxyEdge service which in turn proxies image requests to the Glance servers running on the DistributedComputeHCI roles.

To determine the number of each nodes create ~/dcn0/roles-counts.yaml with the following:

parameter_defaults:
  ControllerCount: 0
  ComputeCount: 0
  DistributedComputeHCICount: 3
  DistributedComputeHCIScaleOutCount: 1

If you do not wish to hyper-converge the compute nodes with Ceph OSD services, then substitute DistributedCompute for DistributedComputeHCI, DistributedComputeScaleOut for DistributedComputeHCIScaleOut, and add CephStorage nodes. The DistributedCompute role contains the GlanceApiEdge service so that the Compute service uses its the local Glance and local Ceph server at the dcn0 site. The DistributedComputeScaleOut contains the HAproxyEdge service so that any compute instances booting on the DistributedComputeScaleOut node proxy their request for images to the Glance services running on the DistributedCompute nodes. It is only necessary to deploy the ScaleOut roles if more than three DistributedComputeHCI or DistributedCompute nodes are necessary. Unlike the DistributedComputeHCI role, there is no minimum number of DistributedCompute required.

Deploy the dcn0 stack

Deploy the dcn0 stack:

openstack overcloud deploy \
     --stack dcn0 \
     --templates /usr/share/openstack-tripleo-heat-templates/ \
     -r ~/dcn0/dcn_roles.yaml \
     -n ~/network-data.yaml \
     -e /usr/share/openstack-tripleo-heat-templates/environments/net-multiple-nics.yaml \
     -e /usr/share/openstack-tripleo-heat-templates/environments/network-isolation.yaml \
     -e /usr/share/openstack-tripleo-heat-templates/environments/network-environment.yaml \
     -e /usr/share/openstack-tripleo-heat-templates/environments/disable-telemetry.yaml \
     -e /usr/share/openstack-tripleo-heat-templates/environments/podman.yaml \
     -e /usr/share/openstack-tripleo-heat-templates/environments/ceph-ansible/ceph-ansible.yaml \
     -e /usr/share/openstack-tripleo-heat-templates/environments/dcn-hci.yaml \
     -e ~/control-plane-export.yaml \
     -e ~/central_ceph_external.yaml \
     -e ~/dcn0/dcn_ceph_keys.yaml \
     -e ~/dcn0/role-counts.yaml \
     -e ~/dcn0/ceph.yaml \
     -e ~/dcn0/az.yaml \
     -e ~/dcn0/glance.yaml

The network related files are included to make the example complete but are not displayed in this document. For more information on configuring networks with distributed compute nodes see Distributed Compute Node deployment.

The environments/cinder-volume-active-active.yaml file is NOT used to configure Cinder active/active on the DCN site because environments/dcn-hci.yaml contains the same parameters. The environments/dcn-hci.yaml file is also used to configure the GlanceApiEdge and HAproxyEdge edge services. If you are not using hyper-converged Ceph, then use environments/dcn.yaml instead. Both environments/dcn-hci.yaml and environments/dcn.yaml use NovaCrossAZAttach: False to override the Nova configuration [cinder] cross_az_attach setting from its default of true. This setting should be false for all nodes in the dcn0 stack so that volumes attached to an instance must be in the same availability zone in Cinder as the instance availability zone in Nova. This is useful when booting an instance from a volume on DCN nodes because Nova will attempt to create a volume using the same availability zone as what is assigned to the instance.

The ~/dcn0/ceph.yaml file contains the following which sets the name of the ceph cluster to “dcn0”:

parameter_defaults:
  CephClusterName: dcn0

The ~/dcn0/ceph.yaml file should also contain additional parameters like CephAnsibleDisksConfig, CephPoolDefaultSize, CephPoolDefaultPgNum to configure the Ceph cluster relative to the available hardware as described in Configuring Ceph with Custom Config Settings.

The ~/dcn0/az.yaml file contains the following:

parameter_defaults:
  ManageNetworks: false
  NovaComputeAvailabilityZone: dcn0
  CinderStorageAvailabilityZone: dcn0
  CinderVolumeCluster: dcn0

CinderVolumeCluster is the name of the Cinder active/active cluster which is deployed per DCN site. The above setting overrides the default of “dcn” to “dcn0” found in environments/dcn-hci.yaml. See Distributed Compute Node deployment for details on the other parameters above.

The ~/control-plane-export.yaml, ~/dcn0/dcn_ceph_keys.yaml, ~/dcn0/glance.yaml, and role-counts.yaml files were created in the previous steps. The ~/central_ceph_external.yaml file should also have been created in a previous step. Deployment with this file is only necessary if images on DCN sites will be pushed back to the central site so that they may then be shared with other DCN sites. This may be useful for sharing snapshots between sites.

Deploy additional DCN sites

All of the previous sections which were done for dcn0 may be repeated verbatim except with “dcn1” substituted for “dcn0” and a new cephx key should be generated for each DCN site as described under Create extra Ceph key. Other than that, the same process may be continued to deploy as many DCN sites as needed. Once all of the desired DCN sites have been deployed proceed to the next section. The ~/control-plane-export.yaml and ~/central_ceph_external.yaml which were created earlier may be reused for each DCN deployment and do not need to be recreated. The roles in the previous section were created specifically for dcn0 to allow for variations between DCN sites.

Update central site to use additional Ceph clusters as Glance stores

Once all of the desired DCN sites are deployed the central site needs to be updated so that the central Glance service may push images to the DCN sites.

In this example only one additional DCN site, dcn1, has been deployed as indicated by the list of undercloud Heat stacks:

$ openstack stack list -c "Stack Name" -c "Stack Status"
+---------------+-----------------+
| Stack Name    | Stack Status    |
+---------------+-----------------+
| dcn1          | CREATE_COMPLETE |
| dcn0          | CREATE_COMPLETE |
| control-plane | CREATE_COMPLETE |
+---------------+-----------------+
$

Create ~/control-plane/glance_update.yaml with content like the following:

parameter_defaults:
  GlanceShowMultipleLocations: true
  GlanceEnabledImportMethods: web-download,copy-image
  GlanceBackend: rbd
  GlanceStoreDescription: 'central rbd glance store'
  CephClusterName: central
  GlanceMultistoreConfig:
    dcn0:
      GlanceBackend: rbd
      GlanceStoreDescription: 'dcn0 rbd glance store'
      CephClientUserName: 'external'
      CephClusterName: dcn0
    dcn1:
      GlanceBackend: rbd
      GlanceStoreDescription: 'dcn1 rbd glance store'
      CephClientUserName: 'external'
      CephClusterName: dcn1

The above will configure the Glance service running on the Controllers to use two additional stores called “dcn0” and “dcn1”.

Create ~/control-plane/dcn_ceph_external.yaml with content like the following:

parameter_defaults:
  CephExternalMultiConfig:
    - cluster: "dcn0"
      fsid: "539e2b96-316e-4c23-b7df-035a3037ddd1"
      external_cluster_mon_ips: "172.16.11.61, 172.16.11.64, 172.16.11.66"
      keys:
        - name: "client.external"
          caps:
            mgr: "allow *"
            mon: "profile rbd"
            osd: "profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images"
          key: "AQBO/mteAAAAABAAc4mVMTpq7OFtrPlRFqN+FQ=="
          mode: "0600"
      dashboard_enabled: false
      ceph_conf_overrides:
        client:
          keyring: /etc/ceph/dcn0.client.external.keyring
    - cluster: "dcn1"
      fsid: "7504a91e-5a0f-4408-bb55-33c3ee2c67e9"
      external_cluster_mon_ips: "172.16.11.182, 172.16.11.185, 172.16.11.187"
      keys:
        - name: "client.external"
          caps:
            mgr: "allow *"
            mon: "profile rbd"
            osd: "profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images"
          key: "AQACCGxeAAAAABAAHocX/cnygrVnLBrKiZHJfw=="
          mode: "0600"
      dashboard_enabled: false
      ceph_conf_overrides:
        client:
          keyring: /etc/ceph/dcn1.client.external.keyring

The CephExternalMultiConfig section of the above is used to configure the Glance service at the central site as a Ceph client of all of the Ceph clusters of the DCN sites; that is “dcn0” and “dcn1” in this example. This will be possible because the central nodes will have the following files created:

  • /etc/ceph/dcn0.conf

  • /etc/ceph/dcn0.client.external.keyring

  • /etc/ceph/dcn1.conf

  • /etc/ceph/dcn1.client.external.keyring

All of the values under CephExternalMultiConfig, except external_cluster_mon_ips, for this section may be obtained from the config-download directory as described in TripleO config-download User’s Guide: Deploying with Ansible. Based on the examples in this document the relevant files with the desired values are /var/lib/mistral/dcn0/ceph-ansible/group_vars/all.yml and /var/lib/mistral/dcn1/ceph-ansible/group_vars/all.yml.

For example, the fsid and cluster (name) for dcn0 may be found like this:

cd /var/lib/mistral/dcn0/ceph-ansible/group_vars/
grep fsid: all.yml
grep name: all.yml

The keys section for dcn0 should contain the same list item that was passed to the CephExtraKeys parameter in an earlier step of this procedure. The key value may also be obtained by looking at the key used by the client.external name in the openstack_keys list found in all.yml. For example, all.yml should contain something which looks like the following and the second item in the list should be used to get the value because it has name set to client.external:

openstack_keys:
-   caps:
        mgr: allow *
        mon: profile rbd
        osd: profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images
    key: AQB7/mteAAAAABAAZzufVwFpSN4Hg2TCsR5AfA==
    mode: '0600'
    name: client.openstack
-   caps:
        mgr: allow *
        mon: profile rbd
        osd: profile rbd pool=vms, profile rbd pool=volumes, profile rbd pool=images
    key: AQBO/mteAAAAABAAc4mVMTpq7OFtrPlRFqN+FQ==
    mode: '0600'
    name: client.external

To determine the value for external_cluster_mon_ips to provide within the CephExternalMultiConfig parameter for dcn0, use the inventory generated by config-download and select the storage IP or storage hostname of every node which runs the CephMons service. Based on the example provided in this document, the relevant inventory file is /var/lib/mistral/dcn0/inventory.yaml. For example the nodes in the DistributedComputeHCI role run the CephMon service by default on IPs in the storage network so the IPs will be in a section which looks like this:

DistributedComputeHCI:
  hosts:
    dcn0-distributedcomputehci-0:
      ansible_host: 192.168.24.20
      ...
      storage_hostname: dcn0-distributedcomputehci-0.storage.localdomain
      storage_ip: 172.16.11.61
      ...
    dcn0-distributedcomputehci-1:
      ansible_host: 192.168.24.25
      ...
      storage_hostname: dcn0-distributedcomputehci-1.storage.localdomain
      storage_ip: 172.16.11.64
      ...

The storage_ip from each host should be combined in a comma delimited list. In this example the parameter is set to external_cluster_mon_ips: “172.16.11.61, 172.16.11.64, 172.16.11.66”. If necessary, the inventory may be regenerated by running the tripleo-ansible-inventory command as described in TripleO config-download User’s Guide: Deploying with Ansible.

The ceph_conf_overrides section should look like the following:

ceph_conf_overrides:
  client:
    keyring: /etc/ceph/dcn0.client.external.keyring

The above will result in the following lines in /etc/ceph/dcn0.conf on the central nodes which interact with the dcn0 Ceph cluster:

[client]
keyring = /etc/ceph/dcn0.client.external.keyring

The name of the external Ceph cluster, relative to the central node, is dcn0 so the relevant Ceph configuration file is called /etc/ceph/dcn0.conf. Optionally, the path to the key may be confirmed by looking directly on any node running the CephMon service on the dcn0 stack if desired. If the conventions in this document are followed, then it should remain consistent. This directive is necessary so that the Glance service on central site knows which keyring to use when connecting to the central Ceph cluster.

It is necessary to always pass dashboard_enabled: false when using CephExternalMultiConfig as the Ceph dashboard cannot be deployed when configuring an overcloud as a client of an external Ceph cluster.

The second item in the CephExternalMultiConfig list which starts with cluster: “dcn1” may have its values determined exactly as they were determined for cluster: “dcn0”, except the relevant data should come from /var/lib/mistral/dcn1/ceph-ansible/group_vars/all.yml and /var/lib/mistral/dcn1/inventory.yaml. The same pattern may be continued for additional DCN sites which the central site wishes to use as an additional Glance store.

For more information on the CephExternalMultiConfig parameter see Use an external Ceph cluster with the Overcloud.

The number of lines in the ~/control-plane/glance_update.yaml and ~/control-plane/glance_update.yaml files will be proportional to the number of DCN sites deployed.

Run the same openstack overcloud deploy –stack control-plane … command which was run in the previous section but also include the the ~/control-plane/glance_update.yaml and ~/control-plane/dcn_ceph_external.yaml files with a -e. When the stack update is complete, proceed to the next section.

Confirm images may be copied between sites

Ensure you have Glance 3.0.0 or newer as provided by the python3-glanceclient RPM:

$ glance --version
3.0.0

Authenticate to the control-plane using the RC file generated by the stack from the first deployment which contains Keystone. In this example the stack was called “control-plane” so the file to source beofre running Glance commands will be called “control-planerc”.

Confirm the expected stores are available:

$ glance stores-info
+----------+----------------------------------------------------------------------------------+
| Property | Value                                                                            |
+----------+----------------------------------------------------------------------------------+
| stores   | [{"default": "true", "id": "default_backend", "description": "central rbd glance |
|          | store"}, {"id": "http", "read-only": "true"}, {"id": "dcn0", "description":      |
|          | "dcn0 rbd glance store"}, {"id": "dcn1", "description": "dcn1 rbd glance         |
|          | store"}]                                                                         |
+----------+----------------------------------------------------------------------------------+

Assuming an image like cirros-0.4.0-x86_64-disk.img is in the current directory, convert the image from QCOW2 format to RAW format using a command like the following:

qemu-img convert -f qcow2 -O raw cirros-0.4.0-x86_64-disk.img cirros-0.4.0-x86_64-disk.raw

Create an image in Glance default store at the central site as seen in the following example:

glance image-create \
--disk-format raw --container-format bare \
--name cirros --file cirros-0.4.0-x86_64-disk.raw \
--store default_backend

Alternatively, if the image is not in the current directory but in qcow2 format on a web server, then it may be imported and converted in one command by running the following:

glance --verbose image-create-via-import --disk-format qcow2 --container-format bare --name cirros --uri http://download.cirros-cloud.net/0.4.0/cirros-0.4.0-x86_64-disk.img --import-method web-download --stores default_backend

Note

The example above assumes that Glance image format conversion is enabled. Thus, even though –disk-format is set to qcow2, which is the format of the image file, Glance will convert and store the image in raw format after it’s uploaded because the raw format is the optimal setting for Ceph RBD. The conversion may be confirmed by running glance image-show <ID> | grep disk_format after the image is uploaded.

Set an environment variable to the ID of the newly created image:

ID=$(openstack image show cirros -c id -f value)

Copy the image from the default store to the dcn0 and dcn1 stores:

glance image-import $ID --stores dcn0,dcn1 --import-method copy-image

Confirm a copy of the image is in each store by looking at the image properties:

$ openstack image show $ID | grep properties
| properties       | direct_url='rbd://d25504ce-459f-432d-b6fa-79854d786f2b/images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076/snap', locations='[{u'url': u'rbd://d25504ce-459f-432d-b6fa-79854d786f2b/images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076/snap', u'metadata': {u'store': u'default_backend'}}, {u'url': u'rbd://0c10d6b5-a455-4c4d-bd53-8f2b9357c3c7/images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076/snap', u'metadata': {u'store': u'dcn0'}}, {u'url': u'rbd://8649d6c3-dcb3-4aae-8c19-8c2fe5a853ac/images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076/snap', u'metadata': {u'store': u'dcn1'}}]', os_glance_failed_import='', os_glance_importing_to_stores='', os_hash_algo='sha512', os_hash_value='b795f047a1b10ba0b7c95b43b2a481a59289dc4cf2e49845e60b194a911819d3ada03767bbba4143b44c93fd7f66c96c5a621e28dff51d1196dae64974ce240e', os_hidden='False', stores='default_backend,dcn0,dcn1' |

The stores key, which is the last item in the properties map is set to ‘default_backend,dcn0,dcn1’.

On further inspection the direct_url key is set to:

rbd://d25504ce-459f-432d-b6fa-79854d786f2b/images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076/snap

Which contains ‘d25504ce-459f-432d-b6fa-79854d786f2b’, the FSID of the central Ceph cluster, the name of the pool, ‘images’, followed by ‘8083c7e7-32d8-4f7a-b1da-0ed7884f1076’, the Glance image ID and name of the Ceph object.

The properties map also contains locations which is set to similar RBD paths for the dcn0 and dcn1 cluster with their respective FSIDs and pool names. Note that the Glance image ID is consistent in all RBD paths.

If the image were deleted with glance image-delete, then the image would be removed from all three RBD stores to ensure consistency. However, if the glanceclient is >3.1.0, then an image may be deleted from a specific store only by using a syntax like glance stores-delete –store <store_id> <image_id>.

Optionally, run the following on any Controller node from the control-plane stack:

sudo podman exec ceph-mon-$(hostname) rbd --cluster central -p images ls -l

Run the following on any DistributedComputeHCI node from the dcn0 stack:

sudo podman exec ceph-mon-$(hostname) rbd --id external --keyring /etc/ceph/dcn0.client.external.keyring --conf /etc/ceph/dcn0.conf -p images ls -l

Run the following on any DistributedComputeHCI node from the dcn1 stack:

sudo podman exec ceph-mon-$(hostname) rbd --id external --keyring /etc/ceph/dcn1.client.external.keyring --conf /etc/ceph/dcn1.conf -p images ls -l

The results in all cases should produce output like the following:

NAME                                      SIZE   PARENT FMT PROT LOCK
8083c7e7-32d8-4f7a-b1da-0ed7884f1076      44 MiB          2
8083c7e7-32d8-4f7a-b1da-0ed7884f1076@snap 44 MiB          2 yes

When an ephemeral instance is COW booted from the image a similar command in the vms pool should show the same parent image:

$ sudo podman exec ceph-mon-$(hostname) rbd --id external --keyring /etc/ceph/dcn1.client.external.keyring --conf /etc/ceph/dcn1.conf -p vms ls -l
NAME                                      SIZE  PARENT                                           FMT PROT LOCK
2b431c77-93b8-4edf-88d9-1fd518d987c2_disk 1 GiB images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076@snap   2      excl
$

Confirm image-based volumes may be booted as DCN instances

An instance with a persistent root volume may be created on a DCN site by using the active/active Cinder service at the DCN site. Assuming the Glance image created in the previous step is available, identify the image ID and pass it to openstack volume create with the –image option to create a volume based on that image.

IMG_ID=$(openstack image show cirros -c id -f value)
openstack volume create --size 8 --availability-zone dcn0 pet-volume-dcn0 --image $IMG_ID

Once the volume is created identify its volume ID and pass it to openstack server create with the –volume option. This example assumes a flavor, key, security group and network have already been created.

VOL_ID=$(openstack volume show -f value -c id pet-volume-dcn0)
openstack server create --flavor tiny --key-name dcn0-key --network dcn0-network --security-group basic --availability-zone dcn0 --volume $VOL_ID pet-server-dcn0

It is also possible to issue one command to have Nova ask Cinder to create the volume before it boots the instance by passing the –image and –boot-from-volume options as in the shown in the example below:

openstack server create --flavor tiny --image $IMG_ID --key-name dcn0-key --network dcn0-network --security-group basic --availability-zone dcn0 --boot-from-volume 4 pet-server-dcn0

The above will only work if the Nova cross_az_attach setting of the relevant compute node is set to false. This is automatically configured by deploying with environments/dcn-hci.yaml. If the cross_az_attach setting is true (the default), then the volume will be created from the image not in the dcn0 site, but on the default central site (as verified with the rbd command on the central Ceph cluster) and then the instance will fail to boot on the dcn0 site. Even if cross_az_attach is true, it’s still possible to create an instance from a volume by using openstack volume create and then openstack server create as shown earlier.

Optionally, after creating the volume from the image at the dcn0 site and then creating an instance from the existing volume, verify that the volume is based on the image by running the rbd command within a ceph-mon container on the dcn0 site to list the volumes pool.

$ sudo podman exec ceph-mon-$HOSTNAME rbd --cluster dcn0 -p volumes ls -l
NAME                                      SIZE  PARENT                                           FMT PROT LOCK
volume-28c6fc32-047b-4306-ad2d-de2be02716b7 8 GiB images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076@snap   2      excl
$

The following commands may be used to create a Cinder snapshot of the root volume of the instance.

openstack server stop pet-server-dcn0
openstack volume snapshot create pet-volume-dcn0-snap --volume $VOL_ID --force
openstack server start pet-server-dcn0

In the above example the server is stopped to quiesce data for clean a snapshot. The –force option is necessary when creating the snapshot because the volume status will remain “in-use” even when the server is shut down. When the snapshot is completed start the server. Listing the contents of the volumes pool on the dcn0 Ceph cluster should show the snapshot which was created and how it is connected to the original volume and original image.

$ sudo podman exec ceph-mon-$HOSTNAME rbd --cluster dcn0 -p volumes ls -l
NAME                                                                                      SIZE  PARENT                                           FMT PROT LOCK
volume-28c6fc32-047b-4306-ad2d-de2be02716b7                                               8 GiB images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076@snap   2      excl
volume-28c6fc32-047b-4306-ad2d-de2be02716b7@snapshot-a1ca8602-6819-45b4-a228-b4cd3e5adf60 8 GiB images/8083c7e7-32d8-4f7a-b1da-0ed7884f1076@snap   2 yes
$

Confirm image snapshots may be created and copied between sites

A new image called “cirros-snapshot” may be created at the dcn0 site from the instance created in the previous section by running the following commands.

NOVA_ID=$(openstack server show pet-server-dcn0 -f value -c id)
openstack server stop $NOVA_ID
openstack server image create --name cirros-snapshot $NOVA_ID
openstack server start $NOVA_ID

In the above example the instance is stopped to quiesce data for clean a snapshot image and is then restarted after the image has been created. The output of openstack image show $IMAGE_ID -f value -c properties should contain a JSON data structure whose key called stores should only contain “dcn0” as that is the only store which has a copy of the new cirros-snapshot image.

The new image may then by copied from the dcn0 site to the central site, which is the default backend for Glance.

IMAGE_ID=$(openstack image show cirros-snapshot -f value -c id)
glance image-import $IMAGE_ID --stores default_backend --import-method copy-image

After the above is run the output of openstack image show $IMAGE_ID -f value -c properties should contain a JSON data structure whose key called stores should looke like “dcn0,default_backend” as the image will also exist in the “default_backend” which stores its data on the central Ceph cluster. The same image at the Central site may then be copied to other DCN sites, booted in the vms or volumes pool, and snapshotted so that the same process may repeat.