Chapter 11. Scaling the Ceph Cluster

11.1. Scaling Up the Ceph Cluster

You can scale up the number of Ceph Storage nodes in your overcloud by re-running the deployment with the number of Ceph Storage nodes you need.

Before doing so, ensure that you have enough nodes for the updated deployment. These nodes must be registered with the director and tagged accordingly.

Registering New Ceph Storage Nodes

To register new Ceph storage nodes with the director, follow these steps:

  1. Log into the director host as the stack user and initialize your director configuration:

    $ source ~/stackrc
  2. Define the hardware and power management details for the new nodes in a new node definition template; for example, instackenv-scale.json.
  3. Import this file to the OpenStack director:

    $ openstack overcloud node import ~/instackenv-scale.json

    Importing the node definition template registers each node defined there to the director.

  4. Assign the kernel and ramdisk images to all nodes:

    $ openstack overcloud node configure
Note

For more information about registering new nodes, see Section 3.2, “Registering Nodes”.

Manually Tagging New Nodes

After registering each node, you will need to inspect the hardware and tag the node into a specific profile. Profile tags match your nodes to flavors, and in turn the flavors are assigned to a deployment role.

To inspect and tag new nodes, follow these steps:

  1. Trigger hardware introspection to retrieve the hardware attributes of each node:

    $ openstack overcloud node introspect --all-manageable --provide
    • The --all-manageable option introspects only nodes in a managed state. In this example, it is all of them.
    • The --provide option resets all nodes to an active state after introspection.

      Important

      Make sure this process runs to completion. This process usually takes 15 minutes for bare metal nodes.

  2. Retrieve a list of your nodes to identify their UUIDs:

    $ openstack baremetal node list
  3. Add a profile option to the properties/capabilities parameter for each node to manually tag a node to a specific profile.

    For example, the following commands tag three additional nodes with the ceph-storage profile:

    $ ironic node-update 551d81f5-4df2-4e0f-93da-6c5de0b868f7 add properties/capabilities='profile:ceph-storage,boot_option:local'
    $ ironic node-update 5e735154-bd6b-42dd-9cc2-b6195c4196d7 add properties/capabilities='profile:ceph-storage,boot_option:local'
    $ ironic node-update 1a2b090c-299d-4c20-a25d-57dd21a7085b add properties/capabilities='profile:ceph-storage,boot_option:local'
Tip

If the nodes you just tagged and registered use multiple disks, you can set the director to use a specific root disk on each node. See Section 3.4, “Defining the root disk” for instructions on how to do so.

Re-deploying the Overcloud with Additional Ceph Storage Nodes

After registering and tagging the new nodes, you can now scale up the number of Ceph Storage nodes by re-deploying the overcloud. When you do, set the CephStorageCount parameter in the parameter_defaults of your environment file (in this case, ~/templates/storage-config.yaml). In Section 8.1, “Assigning Nodes and Flavors to Roles”, the overcloud is configured to deploy with 3 Ceph Storage nodes. To scale it up to 6 nodes instead, use:

parameter_defaults:
  ControllerCount: 3
  OvercloudControlFlavor: control
  ComputeCount: 3
  OvercloudComputeFlavor: compute
  CephStorageCount: 6
  OvercloudCephStorageFlavor: ceph-storage
  CephMonCount: 3
  OvercloudCephMonFlavor: ceph-mon

Upon re-deployment with this setting, the overcloud should now have 6 Ceph Storage nodes instead of 3.

11.2. Scaling Down and Replacing Ceph Storage Nodes

In some cases, you may need to scale down your Ceph cluster, or even replace a Ceph Storage node (for example, if a Ceph Storage node is faulty). In either situation, you need to disable and rebalance any Ceph Storage node you are removing from the Overcloud to ensure no data loss. This procedure explains the process for replacing a Ceph Storage node.

Note

This procedure uses steps from the Red Hat Ceph Storage Administration Guide to manually remove Ceph Storage nodes. For more in-depth information about manual removal of Ceph Storage nodes, see Administering Ceph clusters that run in Containers and Removing a Ceph OSD using the command-line interface.

  1. Log in to a Controller node as the heat-admin user. The director’s stack user has an SSH key to access the heat-admin user.
  2. List the OSD tree and find the OSDs for your node. For example, the node you want to remove might contain the following OSDs:

    -2 0.09998     host overcloud-cephstorage-0
    0 0.04999         osd.0                         up  1.00000          1.00000
    1 0.04999         osd.1                         up  1.00000          1.00000
  3. Disable the OSDs on the Ceph Storage node. In this case, the OSD IDs are 0 and 1.

    [heat-admin@overcloud-controller-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph osd out 0
    [heat-admin@overcloud-controller-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph osd out 1
  4. The Ceph Storage cluster begins rebalancing. Wait for this process to complete. Follow the status using the following command:

    [heat-admin@overcloud-controller-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph -w
  5. After the Ceph cluster completes rebalancing, log in to the Ceph Storage node you are removing (in this case, overcloud-cephstorage-0) as the heat-admin user and stop the node.

    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME systemctl disable ceph-osd@0
    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME systemctl disable ceph-osd@1
  6. Stop the OSDs.

    [heat-admin@overcloud-cephstorage-0 ~]$ sudo systemctl stop ceph-osd@0
    [heat-admin@overcloud-cephstorage-0 ~]$ sudo systemctl stop ceph-osd@1
  7. While logged in to the Controller node, remove the OSDs from the CRUSH map so that they no longer receive data.

    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph osd crush remove osd.0
    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph osd crush remove osd.1
  8. Remove the OSD authentication key.

    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph auth del osd.0
    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph auth del osd.1
  9. Remove the OSD from the cluster.

    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph osd rm 0
    [heat-admin@overcloud-cephstorage-0 ~]$ sudo docker exec ceph-mon-$HOSTNAME ceph osd rm 1
  10. Leave the node and return to the director host as the stack user.

    [heat-admin@overcloud-cephstorage-0 ~]$ exit
    [stack@director ~]$
  11. Disable the Ceph Storage node so the director does not reprovision it.

    [stack@director ~]$ openstack baremetal node list
    [stack@director ~]$ openstack baremetal node maintenance set UUID
  12. Removing a Ceph Storage node requires an update to the overcloud stack in the director using the local template files. First identify the UUID of the Overcloud stack:

    $ openstack stack list
  13. Identify the UUIDs of the Ceph Storage node you want to delete:

    $ openstack server list
  14. Run the following command to delete the node from the stack and update the plan accordingly:

    $ openstack overcloud node delete --stack overcloud NODE_UUID
    Important

    If you passed any extra environment files when you created the overcloud, pass them again here using the -e option to avoid making undesired changes to the overcloud. For more information, see Modifying the Overcloud Environment (from Director Installation and Usage).

  15. Wait until the stack completes its update. Monitor the stack update using the heat stack-list --show-nested command.
  16. Add new nodes to the director’s node pool and deploy them as Ceph Storage nodes. Use the CephStorageCount parameter in the parameter_defaults of your environment file (in this case, ~/templates/storage-config.yaml) to define the total number of Ceph Storage nodes in the Overcloud. For example:

    parameter_defaults:
      ControllerCount: 3
      OvercloudControlFlavor: control
      ComputeCount: 3
      OvercloudComputeFlavor: compute
      CephStorageCount: 3
      OvercloudCephStorageFlavor: ceph-storage
      CephMonCount: 3
      OvercloudCephMonFlavor: ceph-mon
    Note

    See Section 8.1, “Assigning Nodes and Flavors to Roles” for details on how to define the number of nodes per role.

  17. After you update your environment file, re-deploy the overcloud as normal:

    $ openstack overcloud deploy --templates -e ENVIRONMENT_FILES

    The director provisions the new node and updates the entire stack with the new node’s details.

  18. Log in to a Controller node as the heat-admin user and check the status of the Ceph Storage node. For example:

    [heat-admin@overcloud-controller-0 ~]$ sudo ceph status
  19. Confirm that the value in the osdmap section matches the number of desired nodes in your cluster. The Ceph Storage node you removed has now been replaced with a new node.

11.3. Adding an OSD to a Ceph Storage node

This procedure demonstrates how to add an OSD to a node.

Procedure

  1. Notice the following heat template deploys Ceph Storage with three OSD devices:

    parameter_defaults:
      CephAnsibleDisksConfig:
        devices:
          - /dev/sdb
          - /dev/sdc
          - /dev/sdd
        osd_scenario: lvm
        osd_objectstore: bluestore
  2. To add an OSD, update the node disk layout as described in Section 6.2, “Mapping the Ceph Storage Node Disk Layout”. In this example, add /dev/sde to the template:

    parameter_defaults:
      CephAnsibleDisksConfig:
        devices:
          - /dev/sdb
          - /dev/sdc
          - /dev/sdd
          - /dev/sde
        osd_scenario: lvm
        osd_objectstore: bluestore
  3. Run openstack overcloud deploy to update the overcloud.
Note

This example assumes that all hosts with OSDs have a new device called /dev/sde. If you do not want all nodes to have the new device, update the heat template as shown and see Section 6.4, “Mapping the Disk Layout to Non-Homogeneous Ceph Storage Nodes” for information about how to define hosts with a differing devices list.

11.4. Removing an OSD from a Ceph Storage node

This procedure demonstrates how to remove an OSD from a node. It assumes the following about the environment:

  • A server (ceph-storage0) has an OSD (ceph-osd@4) running on /dev/sde.
  • The Ceph monitor service (ceph-mon) is running on controller0.
  • There are enough available OSDs to ensure the storage cluster is not at its near-full ratio.

Procedure

  1. SSH into ceph-storage0 and log in as root.
  2. Disable and stop the OSD service:

    [root@ceph-storage0 ~]# systemctl disable ceph-osd@4
    [root@ceph-stoarge0 ~]# systemctl stop ceph-osd@4
  3. Disconnect from ceph-storage0.
  4. SSH into controller0 and log in as root.
  5. Identify the name of the Ceph monitor container:

    [root@controller0 ~]# podman ps | grep ceph-mon
    ceph-mon-controller0
    [root@controller0 ~]#
  6. Enable the Ceph monitor container to mark the undesired OSD as out:

    [root@controller0 ~]# podman exec ceph-mon-controller0 ceph osd out 4
    Note

    This command causes Ceph to rebalance the storage cluster and copy data to other OSDs in the cluster. The cluster temporarily leaves the active+clean state until rebalancing is complete.

  7. Run the following command and wait for the storage cluster state to become active+clean:

    [root@controller0 ~]# podman exec ceph-mon-controller0 ceph -w
  8. Remove the OSD from the CRUSH map so that it no longer receives data:

    [root@controller0 ~]# podman exec ceph-mon-controller0 ceph osd crush remove osd.4
  9. Remove the OSD authentication key:

    [root@controller0 ~]# podman exec ceph-mon-controller0 ceph auth del osd.4
  10. Remove the OSD:

    [root@controller0 ~]# podman exec ceph-mon-controller0 ceph osd rm 4
  11. Disconnect from controller0.
  12. SSH into the undercloud as the stack user and locate the heat environment file in which you defined the CephAnsibleDisksConfig parameter.
  13. Notice the heat template contains four OSDs:

    parameter_defaults:
      CephAnsibleDisksConfig:
        devices:
          - /dev/sdb
          - /dev/sdc
          - /dev/sdd
          - /dev/sde
        osd_scenario: lvm
        osd_objectstore: bluestore
  14. Modify the template to remove /dev/sde.

    parameter_defaults:
      CephAnsibleDisksConfig:
        devices:
          - /dev/sdb
          - /dev/sdc
          - /dev/sdd
        osd_scenario: lvm
        osd_objectstore: bluestore
  15. Run openstack overcloud deploy to update the overcloud.

    Note

    This example assumes that you removed the /dev/sde device from all hosts with OSDs. If you do not remove the same device from all nodes, update the heat template as shown and see Section 6.4, “Mapping the Disk Layout to Non-Homogeneous Ceph Storage Nodes” for information about how to define hosts with a differing devices list.

11.5. Handling disk failure

If a disk fails, see Handling a Disk Failure in the Red Hat Ceph Storage Operations Guide.