Chapter 1. About OpenShift Virtualization

Learn about OpenShift Virtualization’s capabilities and support scope.

1.1. What you can do with OpenShift Virtualization

OpenShift Virtualization is an add-on to OpenShift Container Platform that allows you to run and manage virtual machine workloads alongside container workloads.

OpenShift Virtualization adds new objects into your OpenShift Container Platform cluster by using Kubernetes custom resources to enable virtualization tasks. These tasks include:

  • Creating and managing Linux and Windows virtual machines (VMs)
  • Running pod and VM workloads alongside each other in a cluster
  • Connecting to virtual machines through a variety of consoles and CLI tools
  • Importing and cloning existing virtual machines
  • Managing network interface controllers and storage disks attached to virtual machines
  • Live migrating virtual machines between nodes

An enhanced web console provides a graphical portal to manage these virtualized resources alongside the OpenShift Container Platform cluster containers and infrastructure.

OpenShift Virtualization is designed and tested to work well with Red Hat OpenShift Data Foundation features.

Important

When you deploy OpenShift Virtualization with OpenShift Data Foundation, you must create a dedicated storage class for Windows virtual machine disks. See Optimizing ODF PersistentVolumes for Windows VMs for details.

You can use OpenShift Virtualization with the OVN-Kubernetes, OpenShift SDN, or one of the other certified network plugins listed in Certified OpenShift CNI Plug-ins.

You can check your OpenShift Virtualization cluster for compliance issues by installing the Compliance Operator and running a scan with the ocp4-moderate and ocp4-moderate-node profiles. The Compliance Operator uses OpenSCAP, a NIST-certified tool, to scan and enforce security policies.

1.1.1. OpenShift Virtualization supported cluster version

OpenShift Virtualization 4.13 is supported for use on OpenShift Container Platform 4.13 clusters. To use the latest z-stream release of OpenShift Virtualization, you must first upgrade to the latest version of OpenShift Container Platform.

1.2. About storage volumes for virtual machine disks

If you use the storage API with known storage providers, volume and access modes are selected automatically. However, if you use a storage class that does not have a storage profile, you must select the volume and access mode.

For best results, use accessMode: ReadWriteMany and volumeMode: Block. This is important for the following reasons:

  • The ReadWriteMany (RWX) access mode is required for live migration.

  • The Block volume mode performs significantly better in comparison to the Filesystem volume mode. This is because the Filesystem volume mode uses more storage layers, including a file system layer and a disk image file. These layers are not necessary for VM disk storage.

    For example, if you use Red Hat OpenShift Data Foundation, Ceph RBD volumes are preferable to CephFS volumes.

    Important

    You cannot live migrate virtual machines that use:

    • A storage volume with ReadWriteOnce (RWO) access mode
    • Passthrough features such as GPUs

    Do not set the evictionStrategy field to LiveMigrate for these virtual machines.

1.3. Single-node OpenShift differences

You can install OpenShift Virtualization on single-node OpenShift.

However, you should be aware that Single-node OpenShift does not support the following features:

  • High availability
  • Pod disruption
  • Live migration
  • Virtual machines or templates that have an eviction strategy configured

1.4. Additional resources