Chapter 1. Introduction

Red Hat OpenStack Platform director creates a cloud environment called the overcloud. The director provides the ability to configure extra features for an overcloud, including integration with Red Hat Ceph Storage (both Ceph Storage clusters created with the director or existing Ceph Storage clusters).

This guide contains instructions for deploying a containerized Red Hat Ceph Storage cluster with your overcloud. Director uses Ansible playbooks provided through the ceph-ansible package to deploy a containerized Ceph cluster. The director also manages the configuration and scaling operations of the cluster.

For more information about containerized services in OpenStack, see Configuring a basic overcloud with the CLI tools in the Director Installation and Usage guide.

1.1. Introduction to Ceph Storage

Red Hat Ceph Storage is a distributed data object store designed to provide excellent performance, reliability, and scalability. Distributed object stores are the future of storage, because they accommodate unstructured data, and because clients can use modern object interfaces and legacy interfaces simultaneously. At the core of every Ceph deployment is the Ceph Storage cluster, which consists of several types of daemons, but primarily, these two:

Ceph OSD (Object Storage Daemon)
Ceph OSDs store data on behalf of Ceph clients. Additionally, Ceph OSDs utilize the CPU and memory of Ceph nodes to perform data replication, rebalancing, recovery, monitoring and reporting functions.
Ceph Monitor
A Ceph monitor maintains a master copy of the Ceph storage cluster map with the current state of the storage cluster.

For more information about Red Hat Ceph Storage, see the Red Hat Ceph Storage Architecture Guide.

1.2. Requirements

This guide contains information supplementary to the Director Installation and Usage guide.

Before you deploy a containerized Ceph Storage cluster with your overcloud, your environment must contain the following configuration:


The Ceph Monitor service installs on the overcloud Controller nodes, so you must provide adequate resources to avoid performance issues. Ensure that the Controller nodes in your environment use at least 16 GB of RAM for memory and solid-state drive (SSD) storage for the Ceph monitor data. For a medium to large Ceph installation, provide at least 500 GB of Ceph monitor data. This space is necessary to avoid levelDB growth if the cluster becomes unstable.

If you use the Red Hat OpenStack Platform director to create Ceph Storage nodes, note the following requirements.

1.2.1. Ceph Storage node requirements

Ceph Storage nodes are responsible for providing object storage in a Red Hat OpenStack Platform environment.

Placement Groups (PGs)
Ceph uses placement groups to facilitate dynamic and efficient object tracking at scale. In the case of OSD failure or cluster rebalancing, Ceph can move or replicate a placement group and its contents, which means a Ceph cluster can re-balance and recover efficiently. The default placement group count that director creates is not always optimal so it is important to calculate the correct placement group count according to your requirements. You can use the placement group calculator to calculate the correct count: Placement Groups (PGs) per Pool Calculator
64-bit x86 processor with support for the Intel 64 or AMD64 CPU extensions.
Red Hat typically recommends a baseline of 16 GB of RAM per OSD host, with an additional 2 GB of RAM per OSD daemon.
Disk layout

Sizing is dependent on your storage requirements. Red Hat recommends that your Ceph Storage node configuration includes three or more disks in a layout similar to the following example:

  • /dev/sda - The root disk. The director copies the main overcloud image to the disk. Ensure that the disk has a minimum of 40 GB of available disk space.
  • /dev/sdb - The journal disk. This disk divides into partitions for Ceph OSD journals. For example, /dev/sdb1, /dev/sdb2, and /dev/sdb3. The journal disk is usually a solid state drive (SSD) to aid with system performance.
  • /dev/sdc and onward - The OSD disks. Use as many disks as necessary for your storage requirements.


    Red Hat OpenStack Platform director uses ceph-ansible, which does not support installing the OSD on the root disk of Ceph Storage nodes. This means that you need at least two disks for a supported Ceph Storage node.

Network Interface Cards
A minimum of one 1 Gbps Network Interface Cards, although Red Hat recommends that you use at least two NICs in a production environment. Use additional network interface cards for bonded interfaces or to delegate tagged VLAN traffic. Red Hat recommends that you use a 10 Gbps interface for storage nodes, especially if you want to create an OpenStack Platform environment that serves a high volume of traffic.
Power management
Each Controller node requires a supported power management interface, such as Intelligent Platform Management Interface (IPMI) functionality on the motherboard of the server.

1.3. Additional resources

The /usr/share/openstack-tripleo-heat-templates/environments/ceph-ansible/ceph-ansible.yaml environment file instructs the director to use playbooks derived from the ceph-ansible project. These playbooks are installed in /usr/share/ceph-ansible/ of the undercloud. In particular, the following file contains all the default settings that the playbooks apply:

  • /usr/share/ceph-ansible/group_vars/all.yml.sample

While ceph-ansible uses playbooks to deploy containerized Ceph Storage, do not edit these files to customize your deployment. Instead, use heat environment files to override the defaults set by these playbooks. If you edit the ceph-ansible playbooks directly, your deployment will fail.

For more information about the playbook collection, see the documentation for this project ( to learn more about the playbook collection.

Alternatively, for information about the default settings applied by director for containerized Ceph Storage, see the heat templates in /usr/share/openstack-tripleo-heat-templates/deployment/ceph-ansible.


Reading these templates requires a deeper understanding of how environment files and heat templates work in director. See Understanding Heat Templates and Environment Files for reference.

Lastly, for more information about containerized services in OpenStack, see Configuring a basic overcloud with the CLI tools in the Director Installation and Usage guide.