Initial Planning

For production environments, several factors influence installation. Consider the following questions as you read through the documentation:

  • Which installation method do you want to use? The Installation Methods section provides some information about the quick and advanced installation methods.

  • How many hosts do you require in the cluster? The Environment Scenarios section provides multiple examples of Single Master and Multiple Master configurations.

  • How many pods are required in your cluster? The Sizing Considerations section provides limits for nodes and pods so you can calculate how large your environment needs to be.

  • Is high availability required? High availability is recommended for fault tolerance. In this situation, you might aim to use the Multiple Masters Using Native HA example as a basis for your environment.

  • Which installation type do you want to use: RPM or containerized? Both installations provide a working OpenShift Origin environment, but you might have a preference for a particular method of installing, managing, and updating your services.

Installation Methods

Both the quick and advanced installation methods are supported for development and production environments. If you want to quickly get OpenShift Origin up and running to try out for the first time, use the quick installer and let the interactive CLI guide you through the configuration options relevant to your environment.

For the most control over your cluster’s configuration, you can use the advanced installation method. This method is particularly suited if you are already familiar with Ansible. However, following along with the OpenShift Origin documentation should equip you with enough information to reliably deploy your cluster and continue to manage its configuration post-deployment using the provided Ansible playbooks directly.

If you install initially using the quick installer, you can always further tweak your cluster’s configuration and adjust the number of hosts in the cluster using the same installer tool. If you wanted to later switch to using the advanced method, you can create an inventory file for your configuration and carry on that way.

Sizing Considerations

Determine how many nodes and pods you require for your OpenShift Origin cluster. Cluster scalability correlates to the number of pods in a cluster environment. That number influences the other numbers in your setup.

The following table provides the maximum sizing limits for nodes and pods:

Type Maximum

Maximum nodes per cluster

2000

Maximum pods per cluster

120,000

Maximum pods per node

250

Maximum pods per core

10

Oversubscribing the physical resources on a node affects resource guarantees the Kubernetes scheduler makes during pod placement. Learn what measures you can take to avoid memory swapping.

Determine how many pods are expected to fit per node:

Maximum Pods per Cluster / Expected Pods per Node = Total Number of Nodes
Example Scenario

If you want to scope your cluster for 2200 pods per cluster, you would need at least 9 nodes, assuming that there are 250 maximum pods per node:

2200 / 250 = 8.8

If you increase the number of nodes to 20, then the pod distribution changes to 110 pods per node:

2200 / 20 = 110

Environment Scenarios

This section outlines different examples of scenarios for your OpenShift Origin environment. Use these scenarios as a basis for planning your own OpenShift Origin cluster.

Moving from a single master cluster to multiple masters after installation is not supported.

Single Master and Multiple Nodes

The following table describes an example environment for a single master (with etcd installed on the same host) and two nodes:

Host Name Infrastructure Component to Install

master.example.com

Master and node

master.example.com

etcd

node1.example.com

Node

node2.example.com

Single Master, Multiple etcd, and Multiple Nodes

The following table describes an example environment for a single master, three etcd hosts, and two nodes:

Host Name Infrastructure Component to Install

master.example.com

Master and node

etcd1.example.com

etcd

etcd2.example.com

etcd3.example.com

node1.example.com

Node

node2.example.com

When specifying multiple etcd hosts, external etcd is installed and configured. Clustering of OpenShift Origin’s embedded etcd is not supported.

Multiple Masters Using Native HA

The following describes an example environment for three masters, one HAProxy load balancer, three etcd hosts, and two nodes using the native HA method:

Host Name Infrastructure Component to Install

master1.example.com

Master (clustered using native HA) and node

master2.example.com

master3.example.com

lb.example.com

HAProxy to load balance API master endpoints

etcd1.example.com

etcd

etcd2.example.com

etcd3.example.com

node1.example.com

Node

node2.example.com

When specifying multiple etcd hosts, external etcd is installed and configured. Clustering of OpenShift Origin’s embedded etcd is not supported.

Stand-alone Registry

You can also install OpenShift Origin to act as a stand-alone registry using the OpenShift Origin’s integrated registry. See Installing a Stand-alone Registry for details on this scenario.

RPM vs Containerized

An RPM installation installs all services through package management and configures services to run within the same user space, while a containerized installation installs services using container images and runs separate services in individual containers.

See the Installing on Containerized Hosts topic for more details on configuring your installation to use containerized services.