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Installing a cluster with z/VM on IBM Z and LinuxONE in a restricted network

In OpenShift Container Platform version 4.11, you can install a cluster on IBM Z and LinuxONE infrastructure that you provision in a restricted network.

While this document refers to only IBM Z, all information in it also applies to LinuxONE.

Additional considerations exist for non-bare metal platforms. Review the information in the guidelines for deploying OpenShift Container Platform on non-tested platforms before you install an OpenShift Container Platform cluster.

Prerequisites

About installations in restricted networks

In OpenShift Container Platform 4.11, you can perform an installation that does not require an active connection to the internet to obtain software components. Restricted network installations can be completed using installer-provisioned infrastructure or user-provisioned infrastructure, depending on the cloud platform to which you are installing the cluster.

If you choose to perform a restricted network installation on a cloud platform, you still require access to its cloud APIs. Some cloud functions, like Amazon Web Service’s Route 53 DNS and IAM services, require internet access. Depending on your network, you might require less internet access for an installation on bare metal hardware or on VMware vSphere.

To complete a restricted network installation, you must create a registry that mirrors the contents of the OpenShift Container Platform registry and contains the installation media. You can create this registry on a mirror host, which can access both the internet and your closed network, or by using other methods that meet your restrictions.

Because of the complexity of the configuration for user-provisioned installations, consider completing a standard user-provisioned infrastructure installation before you attempt a restricted network installation using user-provisioned infrastructure. Completing this test installation might make it easier to isolate and troubleshoot any issues that might arise during your installation in a restricted network.

Additional limits

Clusters in restricted networks have the following additional limitations and restrictions:

  • The ClusterVersion status includes an Unable to retrieve available updates error.

  • By default, you cannot use the contents of the Developer Catalog because you cannot access the required image stream tags.

Internet access for OpenShift Container Platform

In OpenShift Container Platform 4.11, you require access to the internet to obtain the images that are necessary to install your cluster.

You must have internet access to:

  • Access OpenShift Cluster Manager Hybrid Cloud Console to download the installation program and perform subscription management. If the cluster has internet access and you do not disable Telemetry, that service automatically entitles your cluster.

  • Access Quay.io to obtain the packages that are required to install your cluster.

  • Obtain the packages that are required to perform cluster updates.

If your cluster cannot have direct internet access, you can perform a restricted network installation on some types of infrastructure that you provision. During that process, you download the required content and use it to populate a mirror registry with the installation packages. With some installation types, the environment that you install your cluster in will not require internet access. Before you update the cluster, you update the content of the mirror registry.

Requirements for a cluster with user-provisioned infrastructure

For a cluster that contains user-provisioned infrastructure, you must deploy all of the required machines.

This section describes the requirements for deploying OpenShift Container Platform on user-provisioned infrastructure.

Required machines for cluster installation

The smallest OpenShift Container Platform clusters require the following hosts:

Table 1. Minimum required hosts
Hosts Description

One temporary bootstrap machine

The cluster requires the bootstrap machine to deploy the OpenShift Container Platform cluster on the three control plane machines. You can remove the bootstrap machine after you install the cluster.

Three control plane machines

The control plane machines run the Kubernetes and OpenShift Container Platform services that form the control plane.

At least two compute machines, which are also known as worker machines.

The workloads requested by OpenShift Container Platform users run on the compute machines.

To improve high availability of your cluster, distribute the control plane machines over different z/VM instances on at least two physical machines.

The bootstrap, control plane, and compute machines must use Red Hat Enterprise Linux CoreOS (RHCOS) as the operating system.

Note that RHCOS is based on Red Hat Enterprise Linux (RHEL) 8 and inherits all of its hardware certifications and requirements. See Red Hat Enterprise Linux technology capabilities and limits.

Minimum resource requirements for cluster installation

Each cluster machine must meet the following minimum requirements:

Table 2. Minimum resource requirements
Machine Operating System vCPU [1] Virtual RAM Storage IOPS

Bootstrap

RHCOS

4

16 GB

100 GB

N/A

Control plane

RHCOS

4

16 GB

100 GB

N/A

Compute

RHCOS

2

8 GB

100 GB

N/A

  1. One physical core (IFL) provides two logical cores (threads) when SMT-2 is enabled. The hypervisor can provide two or more vCPUs.

If an instance type for your platform meets the minimum requirements for cluster machines, it is supported to use in OpenShift Container Platform.

Minimum IBM Z system environment

You can install OpenShift Container Platform version 4.11 on the following IBM hardware:

  • IBM z16 (all models), IBM z15 (all models), IBM z14 (all models), IBM z13, and IBM z13s

  • LinuxONE, any version

Hardware requirements

  • The equivalent of six Integrated Facilities for Linux (IFL), which are SMT2 enabled, for each cluster.

  • At least one network connection to both connect to the LoadBalancer service and to serve data for traffic outside the cluster.

You can use dedicated or shared IFLs to assign sufficient compute resources. Resource sharing is one of the key strengths of IBM Z. However, you must adjust capacity correctly on each hypervisor layer and ensure sufficient resources for every OpenShift Container Platform cluster.

Since the overall performance of the cluster can be impacted, the LPARs that are used to setup the OpenShift Container Platform clusters must provide sufficient compute capacity. In this context, LPAR weight management, entitlements, and CPU shares on the hypervisor level play an important role.

Operating system requirements

  • One instance of z/VM 7.1 or later

On your z/VM instance, set up:

  • Three guest virtual machines for OpenShift Container Platform control plane machines

  • Two guest virtual machines for OpenShift Container Platform compute machines

  • One guest virtual machine for the temporary OpenShift Container Platform bootstrap machine

IBM Z network connectivity requirements

To install on IBM Z under z/VM, you require a single z/VM virtual NIC in layer 2 mode. You also need:

  • A direct-attached OSA or RoCE network adapter

  • A z/VM VSwitch set up. For a preferred setup, use OSA link aggregation.

Disk storage for the z/VM guest virtual machines

  • FICON attached disk storage (DASDs). These can be z/VM minidisks, fullpack minidisks, or dedicated DASDs, all of which must be formatted as CDL, which is the default. To reach the minimum required DASD size for Red Hat Enterprise Linux CoreOS (RHCOS) installations, you need extended address volumes (EAV). If available, use HyperPAV to ensure optimal performance.

  • FCP attached disk storage

Storage / Main Memory

  • 16 GB for OpenShift Container Platform control plane machines

  • 8 GB for OpenShift Container Platform compute machines

  • 16 GB for the temporary OpenShift Container Platform bootstrap machine

Preferred IBM Z system environment

Hardware requirements

  • 3 LPARS that each have the equivalent of 6 IFLs, which are SMT2 enabled, for each cluster.

  • Two network connections to connect to both connect to the LoadBalancer service and to serve data for traffic outside the cluster.

  • HiperSockets, which are attached to a node either directly as a device or by bridging with one z/VM VSWITCH to be transparent to the z/VM guest. To directly connect HiperSockets to a node, you must set up a gateway to the external network via a RHEL 8 guest to bridge to the HiperSockets network.

Operating system requirements

  • 2 or 3 instances of z/VM 7.1 or later for high availability

On your z/VM instances, set up:

  • 3 guest virtual machines for OpenShift Container Platform control plane machines, one per z/VM instance.

  • At least 6 guest virtual machines for OpenShift Container Platform compute machines, distributed across the z/VM instances.

  • 1 guest virtual machine for the temporary OpenShift Container Platform bootstrap machine.

  • To ensure the availability of integral components in an overcommitted environment, increase the priority of the control plane by using the CP command SET SHARE. Do the same for infrastructure nodes, if they exist. See SET SHARE in IBM Documentation.

IBM Z network connectivity requirements

To install on IBM Z under z/VM, you require a single z/VM virtual NIC in layer 2 mode. You also need:

  • A direct-attached OSA or RoCE network adapter

  • A z/VM VSwitch set up. For a preferred setup, use OSA link aggregation.

Disk storage for the z/VM guest virtual machines
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