Chapter 2. Ceph Storage node requirements

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

Placement Groups
Ceph uses Placement Groups to facilitate dynamic and efficient object tracking at scale. In the case of OSD failure or cluster re-balancing, 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 16GB of RAM per OSD host, with an additional 2 GB of RAM per OSD daemon.
Disk Layout

Sizing is dependant on your storage need. The recommended Red Hat Ceph Storage node configuration requires at least 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. This should be at minimum 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, /dev/sdb3, and onward. 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 you need at least two or more disks for a supported Ceph Storage node.

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

This guide also requires the following:


The Ceph Monitor service is installed on the Overcloud’s Controller nodes. This means you must provide adequate resources to alleviate performance issues. Ensure 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.

2.1. 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 lists all the default settings applied by the playbooks:

  • /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. Doing this will result in a failed deployment. Rather, use Heat environment files to override the defaults set by these playbooks.

You can also consult the documentation of this project ( to learn more about the playbook collection.

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


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.