Chapter 5. Customizing the storage service

Director applies basic, default settings to the deployed Red Hat Ceph Storage cluster. You must define additional configuration in a custom environment file.

Placement groups (PGs) facilitate dynamic and efficient object tracking at scale. In the event of OSD failure or Ceph Storage cluster rebalancing, Ceph can move or replicate a placement group and the contents of the placement group. This allows a Ceph Storage cluster to rebalance and recover efficiently.

The placement group and replica count settings are not changed from the defaults unless the following parameters are included in a Ceph configuration file:

When the overcloud is deployed with the openstack overcloud deploy command, a pool is created for every enabled Red Hat OpenStack Platform service. For example, the following command creates pools for the Compute service (nova), the Block Storage service (cinder), and the Image service (glance):

openstack overcloud deploy --templates \
  -e /usr/share/openstack-tripleo-heat-templates/environments/cephadm/cephadm-rbd-only.yaml

Adding -e environments/cinder-backup.yaml to the command, creates a pool called backups:

openstack overcloud deploy --templates \
  -e /usr/share/openstack-tripleo-heat-templates/environments/cephadm/cephadm-rbd-only.yaml
  -e environments/cinder-backup.yaml

It is not necessary to configure a placement group number per pool; the pg_autoscale_mode attribute is enabled by default. However, it is recommended to configure the target_size_ratio or pg_num attributes. This minimimzes data rebalancing.

To set the target_size_ratio attribute per pool, use a configuration file entry similar to the following example:

parameter_defaults:
  CephPools:
    - name: volumes
      target_size_ratio: 0.4
      application: rbd
    - name: images
      target_size_ratio: 0.1
      application: rbd
    - name: vms
      target_size_ratio: 0.3
      application: rbd

In this example, the percentage of data used per service will be:

Set these values based on your expected usage . If you do not override the CephPools parameter, each pool uses the default placement group number. Though the autoscaler will adjust this number automatically over time based on usage, the data will be moved within the Ceph cluster. This uses computational resources.

If you prefer to set a placement group number instead of a target size ratio, replace target_size_ratio in the example with pg_num. Use a different integer per pool based on your expected usage.

See the Red Hat Ceph Storage Hardware Guide for Red Hat Ceph Storage processor, network interface card, and power management interface recommendations.

The Ceph Metadata Server (MDS) runs the ceph-mds daemon. This daemon manages metadata related to files stored on CephFS. CephFS can be consumed natively or through the NFS protocol.

The Ceph Object Gateway (RGW) provides an interface to access object storage capabilities within a Red Hat Ceph Storage cluster.

When you use director to deploy Ceph, director automatically enables RGW. This is a direct replacement for the Object Storage service (swift). Services that normally use the Object Storage service can use RGW instead without additional configuration. The Object Storage service remains available as an object storage option for upgraded Ceph clusters.

There is no requirement for a separate RGW environment file to enable it. For more information about environment files for other object storage options, see Section 5.5, “Deployment options for Red Hat OpenStack Platform object storage”.

By default, Ceph Storage allows 250 placement groups per Object Storage Daemon (OSD). When you enable RGW, Ceph Storage creates the following six additional pools required by RGW:

There are three options for deploying overcloud object storage:

The Block Storage Backup service (cinder-backup) is disabled by default. It must be enabled to use it with Ceph.

`/usr/share/openstack-tripleo-heat-templates/environments/cinder-backup.yaml`.

Use a bonded interface to combine multiple NICs and add redundancy to a network connection. If you have enough NICs on your Ceph nodes, you can create multiple bonded interfaces on each node to expand redundancy capability.

Use a bonded interface for each network connection the node requires. This provides both redundancy and a dedicated connection for each network.

See Provisioning the overcloud networks in the Installing and managing Red Hat OpenStack Platform with director guide for information and procedures.