Chapter 5. Customizing the Ceph Storage cluster

Director deploys containerized Red Hat Ceph Storage using a default configuration. You can customize Ceph Storage by overriding the default settings.

Prerequistes

To deploy containerized Ceph Storage you must include the /usr/share/openstack-tripleo-heat-templates/environments/ceph-ansible/ceph-ansible.yaml file during overcloud deployment. This environment file defines the following resources:

Use these resources to override any defaults that the director sets for containerized Ceph Storage.

Procedure

  1. Enable the Red Hat Ceph Storage 4 Tools repository: 

    $ sudo subscription-manager repos --enable=rhceph-4-tools-for-rhel-8-x86_64-rpms

  2. Install the ceph-ansible package on the undercloud: 

    $ sudo dnf install ceph-ansible

  3. To customize your Ceph Storage cluster, define custom parameters in a new environment file, for example, /home/stack/templates/ceph-config.yaml. You can apply Ceph Storage cluster settings with the following syntax in the parameter_defaults section of your environment file: 

    parameter_defaults:
  CephConfigOverrides:
    section:
      KEY:VALUE
    Note

    You can apply the CephConfigOverrides parameter to the [global] section of the ceph.conf file, as well as any other section, such as [osd], [mon], and [client]. If you specify a section, the key:value data goes into the specified section. If you do not specify a section, the data goes into the [global] section by default. For information about Ceph Storage configuration, customization, and supported parameters, see Red Hat Ceph Storage Configuration Guide.

  4. Replace KEY and VALUE with the Ceph cluster settings that you want to apply. For example, in the global section, max_open_files is the KEY and 131072 is the corresponding VALUE: 

    parameter_defaults:
  CephConfigOverrides:
    global:
      max_open_files: 131072
    osd:
      osd_scrub_during_recovery: false

    This configuration results in the following settings defined in the configuration file of your Ceph cluster: 

    [global]
max_open_files = 131072
[osd]
osd_scrub_during_recovery = false

5.1. Setting ceph-ansible group variables

The ceph-ansible tool is a playbook used to install and manage Ceph Storage clusters.

The ceph-ansible tool has a group_vars directory that defines configuration options and the default settings for those options. Use the group_vars directory to set Ceph Storage parameters.

For information about the group_vars directory, see Installing a Red Hat Ceph Storage cluster in the Installation Guide.

To change the variable defaults in director, use the CephAnsibleExtraConfig parameter to pass the new values in heat environment files. For example, to set the ceph-ansible group variable journal_size to 40960, create an environment file with the following journal_size definition: 

parameter_defaults:
  CephAnsibleExtraConfig:
    journal_size: 40960
Important

Change ceph-ansible group variables with the override parameters; do not edit group variables directly in the /usr/share/ceph-ansible directory on the undercloud.

5.2. Ceph containers for Red Hat OpenStack Platform with Ceph Storage

A Ceph container is required to configure Red Hat OpenStack Platform (RHOSP) to use Ceph, even with an external Ceph cluster. To be compatible with Red Hat Enterprise Linux 8, RHOSP 16.0 requires Red Hat Ceph Storage 4. The Ceph Storage 4 container is hosted at registry.redhat.io, a registry which requires authentication.

You can use the heat environment parameter ContainerImageRegistryCredentials to authenticate at registry.redhat.io, as described in Container image preparation parameters.

5.3. Mapping the Ceph Storage node disk layout

When you deploy containerized Ceph Storage, you must map the disk layout and specify dedicated block devices for the Ceph OSD service. You can perform this mapping in the environment file that you created earlier to define your custom Ceph parameters: /home/stack/templates/ceph-config.yaml.

Use the CephAnsibleDisksConfig resource in parameter_defaults to map your disk layout. This resource uses the following variables:

VariableRequired?Default value (if unset)Description

osd_scenario

Yes

lvm

NOTE: The default value is lvm.

The lvm value allows ceph-ansible to use ceph-volume to configure OSDs and BlueStore WAL devices.

devices

Yes

NONE. Variable must be set.

A list of block devices that you want to use for OSDs on the node.

dedicated_devices

Yes (only if osd_scenario is non-collocated)

devices

A list of block devices that maps each entry in the devices parameter to a dedicated journaling block device. You can use this variable only when osd_scenario=non-collocated.

dmcrypt

No

false

Sets whether data stored on OSDs is encrypted (true) or unencrypted (false).

osd_objectstore

No

bluestore

NOTE: The default value is bluestore.

Sets the storage back end used by Ceph.

5.3.1. Using BlueStore

To specify the block devices that you want to use as Ceph OSDs, use a variation of the following snippet: 

parameter_defaults:
  CephAnsibleDisksConfig:
    devices:
      - /dev/sdb
      - /dev/sdc
      - /dev/sdd
      - /dev/nvme0n1
    osd_scenario: lvm
    osd_objectstore: bluestore

Because /dev/nvme0n1 is in a higher performing device class, the example parameter defaults produce three OSDs that run on /dev/sdb, /dev/sdc, and /dev/sdd. The three OSDs use /dev/nvme0n1 as a BlueStore WAL device. The ceph-volume tool does this by using the batch subcommand. The same setup is duplicated for each Ceph storage node and assumes uniform hardware. If the BlueStore WAL data resides on the same disks as the OSDs, then change the parameter defaults: 

parameter_defaults:
  CephAnsibleDisksConfig:
    devices:
      - /dev/sdb
      - /dev/sdc
      - /dev/sdd
    osd_scenario: lvm
    osd_objectstore: bluestore

5.3.2. Referring to devices with persistent names

In some nodes, disk paths, such as /dev/sdb and /dev/sdc, may not point to the same block device during reboots. If this is the case with your CephStorage nodes, specify each disk with the /dev/disk/by-path/ symlink to ensure that the block device mapping is consistent throughout deployments: 

parameter_defaults:
  CephAnsibleDisksConfig:
    devices:

      - /dev/disk/by-path/pci-0000:03:00.0-scsi-0:0:10:0
      - /dev/disk/by-path/pci-0000:03:00.0-scsi-0:0:11:0


    dedicated_devices
      - /dev/nvme0n1
      - /dev/nvme0n1

Because you must set the list of OSD devices prior to overcloud deployment, it may not be possible to identify and set the PCI path of disk devices. In this case, gather the /dev/disk/by-path/symlink data for block devices during introspection.

In the following example, run the first command to download the introspection data from the undercloud Object Storage service (swift) for the server b08-h03-r620-hci and saves the data in a file called b08-h03-r620-hci.json. Run the second command to grep for “by-path”. The output of this command contains the unique /dev/disk/by-path values that you can use to identify disks. 

(undercloud) [stack@b08-h02-r620 ironic]$ openstack baremetal introspection data save b08-h03-r620-hci | jq . > b08-h03-r620-hci.json
(undercloud) [stack@b08-h02-r620 ironic]$ grep by-path b08-h03-r620-hci.json
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:0:0",
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:1:0",
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:3:0",
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:4:0",
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:5:0",
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:6:0",
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:7:0",
        "by_path": "/dev/disk/by-path/pci-0000:02:00.0-scsi-0:2:0:0",

For more information about naming conventions for storage devices, see Overview of persistent naming attributes in the Managing storage devices guide.

For details about each journaling scenario and disk mapping for containerized Ceph Storage, see the OSD Scenarios section of the project documentation for ceph-ansible.

5.4. Assigning custom attributes to different Ceph pools

By default, Ceph pools created with director have the same number of placement groups (pg_num and pgp_num) and sizes. You can use either method in Chapter 5, Customizing the Ceph Storage cluster to override these settings globally; that is, doing so applies the same values for all pools.

You can also apply different attributes to each Ceph pool. To do so, use the CephPools parameter: 

parameter_defaults:
  CephPools:
    - name: POOL
      pg_num: 128
      application: rbd

Replace POOL with the name of the pool that you want to configure and the pg_num setting to indicate the number of placement groups. This overrides the default pg_num for the specified pool.

If you use the CephPools parameter, you must also specify the application type. The application type for Compute, Block Storage, and Image Storage should be rbd, as shown in the examples, but depending on what the pool is used for, you might need to specify a different application type. For example, the application type for the gnocchi metrics pool is openstack_gnocchi. For more information, see Enable Application in the Storage Strategies Guide .

If you do not use the CephPools parameter, director sets the appropriate application type automatically, but only for the default pool list.

You can also create new custom pools through the CephPools parameter. For example, to add a pool called custompool: 

parameter_defaults:
  CephPools:
    - name: custompool
      pg_num: 128
      application: rbd

This creates a new custom pool in addition to the default pools.

Tip

For typical pool configurations of common Ceph use cases, see the Ceph Placement Groups (PGs) per Pool Calculator. This calculator is normally used to generate the commands for manually configuring your Ceph pools. In this deployment, the director will configure the pools based on your specifications.

Warning

Red Hat Ceph Storage 3 (Luminous) introduced a hard limit on the maximum number of PGs an OSD can have, which is 200 by default. Do not override this parameter beyond 200. If there is a problem because the Ceph PG number exceeds the maximum, adjust the pg_num per pool to address the problem, not the mon_max_pg_per_osd.

5.5. Mapping the disk layout to non-homogeneous Ceph Storage nodes

By default, all nodes of a role that host Ceph OSDs (indicated by the OS::TripleO::Services::CephOSD service in roles_data.yaml), for example CephStorage or ComputeHCI nodes, use the global devices and dedicated_devices lists set in Section 5.3, “Mapping the Ceph Storage node disk layout”. This assumes that all of these servers have homogeneous hardware. If a subset of these servers do not have homogeneous hardware, then director needs to be aware that each of these servers has different devices and dedicated_devices lists. This is known as a node-specific disk configuration.

To pass a node-specific disk configuration to director, you must pass a heat environment file, such as node-spec-overrides.yaml, to the openstack overcloud deploy command and the file content must identify each server by a machine unique UUID and a list of local variables to override the global variables.

You can extract the machine unique UUID for each individual server or from the Ironic database.

To locate the UUID for an individual server, log in to the server and enter the following command: 

dmidecode -s system-uuid

To extract the UUID from the Ironic database, enter the following command on the undercloud: 

openstack baremetal introspection data save NODE-ID | jq .extra.system.product.uuid
Warning

If the undercloud.conf does not have inspection_extras = true before undercloud installation or upgrade and introspection, then the machine unique UUID is not in the Ironic database.

Important

The machine unique UUID is not the Ironic UUID.

A valid node-spec-overrides.yaml file might look like the following: 

parameter_defaults:
  NodeDataLookup: {"32E87B4C-C4A7-418E-865B-191684A6883B": {"devices": ["/dev/sdc"]}}

All lines after the first two lines must be valid JSON. An easy way to verify that the JSON is valid is to use the jq command:

  1. Remove the first two lines (parameter_defaults: and NodeDataLookup:) from the file temporarily.
  2. Enter cat node-spec-overrides.yaml | jq .

As the node-spec-overrides.yaml file grows, jq might also be used to ensure that the embedded JSON is valid. For example, because the devices and dedicated_devices list must be the same length, use the following command to verify that they are the same length before you start the deployment. 

(undercloud) [stack@b08-h02-r620 tht]$ cat node-spec-c05-h17-h21-h25-6048r.yaml | jq '.[] | .devices | length'
33
30
33
(undercloud) [stack@b08-h02-r620 tht]$ cat node-spec-c05-h17-h21-h25-6048r.yaml | jq '.[] | .dedicated_devices | length'
33
30
33
(undercloud) [stack@b08-h02-r620 tht]$

In the above example, the node-spec-c05-h17-h21-h25-6048r.yaml has three servers in rack c05 in which slots h17, h21, and h25 are missing disks. A more complicated example is included at the end of this section.

After the JSON has been validated add back the two lines which makes it a valid environment YAML file (parameter_defaults: and NodeDataLookup:) and include it with a -e in the deployment.

In the example below, the updated heat environment file uses NodeDataLookup for Ceph deployment. All of the servers had a devices list with 35 disks except one of them had a disk missing. This environment file overrides the default devices list for only that single node and gives it the list of 34 disks it must use instead of the global list. 

parameter_defaults:
  # c05-h01-6048r is missing scsi-0:2:35:0 (00000000-0000-0000-0000-0CC47A6EFD0C)
  NodeDataLookup: {
    "00000000-0000-0000-0000-0CC47A6EFD0C": {
      "devices": [
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:1:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:32:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:2:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:3:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:4:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:5:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:6:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:33:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:7:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:8:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:34:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:9:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:10:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:11:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:12:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:13:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:14:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:15:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:16:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:17:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:18:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:19:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:20:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:21:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:22:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:23:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:24:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:25:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:26:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:27:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:28:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:29:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:30:0",
    "/dev/disk/by-path/pci-0000:03:00.0-scsi-0:2:31:0"
        ],
      "dedicated_devices": [
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:81:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1",
    "/dev/disk/by-path/pci-0000:84:00.0-nvme-1"
        ]
      }
    }

5.6. Increasing the restart delay for large Ceph clusters

During deployment, Ceph services such as OSDs and Monitors, are restarted and the deployment does not continue until the service is running again. Ansible waits 15 seconds (the delay) and checks 5 times for the service to start (the retries). If the service does not restart, the deployment stops so the operator can intervene.

Depending on the size of the Ceph cluster, you may need to increase the retry or delay values. The exact names of these parameters and their defaults are as follows: 

 health_mon_check_retries: 5
 health_mon_check_delay: 15
 health_osd_check_retries: 5
 health_osd_check_delay: 15

Procedure

  1. Update the CephAnsibleExtraConfig parameter to change the default delay and retry values: 

    parameter_defaults:
  CephAnsibleExtraConfig:
    health_osd_check_delay: 40
    health_osd_check_retries: 30
    health_mon_check_delay: 20
    health_mon_check_retries: 10

    This example makes the cluster check 30 times and wait 40 seconds between each check for the Ceph OSDs, and check 20 times and wait 10 seconds between each check for the Ceph MONs.

  2. To incorporate the changes, pass the updated yaml file with -e using openstack overcloud deploy.

5.7. Overriding Ansible environment variables

The Red Hat OpenStack Platform Workflow service (mistral) uses Ansible to configure Ceph Storage, but you can customize the Ansible environment by using Ansible environment variables.

Procedure

To override an ANSIBLE_* environment variable, use the CephAnsibleEnvironmentVariables heat template parameter.

This example configuration increases the number of forks and SSH retries: 

parameter_defaults:
  CephAnsibleEnvironmentVariables:
    ANSIBLE_SSH_RETRIES: '6'
    DEFAULT_FORKS: '35'

For more information about Ansible environment variables, see Ansible Configuration Settings.

For more information about how to customize your Ceph Storage cluster, see Customizing the Ceph Storage cluster.