As mentioned earlier, Ansible will be the orchestration tool of choice for this book, so let's look at it in a bit more detail.

Ansible is an agent-less orchestration tool written in Python that uses SSH to carry out configuration tasks on remote nodes. It was first released in 2012, has gained widespread adoption, and is known for its ease of adoption and low learning curve. Red Hat purchased the commercial company Ansible Inc. in 2015 and so has a very well developed and close-knit integration for deploying Ceph.

Files called playbooks are used in Ansible to describe a list of commands, actions, and configurations to be carried out on specified hosts or groups of hosts and are stored in the yaml file format. Instead of having large unmanageable playbooks, Anisble roles can be created to allow a playbook to contain a single task, which may then carry out a number of tasks associated with the role.

The use of SSH to connect to remote nodes and execute playbooks means that it is very lightweight and does not require either an agent or a centralized server.

For testing Ansible also integrates well with Vagrant; an Ansible playbook can be specified as part of the Vagrant provisioning configuration and will automatically generate an inventory file from the VMs Vagrant that has been created and will run the playbook once the servers have booted. This allows a Ceph cluster, including its OS, to be deployed via just a single command.