Kubernetes Cluster Types and Compatibility
An existing HPE Ezmeral Runtime Enterprise deployment that is upgraded from a previous release might contain Kubernetes clusters that use the containerd runtime and Kubernetes clusters that use the Docker runtime. All nodes in a Kubernetes cluster must use the same type of runtime.
HPE Kubernetes Clusters
The container runtime used by Hewlett Packard Enterprise distributions
of Kubernetes is containerd
.
Kubernetes clusters that are created in deployments of Hewlett Packard Enterprise 5.5.0 and later use the containerd runtime. In addition, for worker hosts that are added to the deployment, the default container runtime is also containerd.
Legacy Kubernetes Clusters
Kubernetes cluster that was created on a previous version of HPE Ezmeral Runtime Enterprise and has not been migrated to use the Hewlett Packard Enterprise distribution of Kubernetes is a legacy Kubernetes cluster. Hosts in legacy Kubernetes clusters use the Docker runtime.
Existing legacy Kubernetes clusters can be expanded, but the hosts you add to the cluster must use the Docker container runtime. Additional steps are required to prepare the host before you add the host to the deployment. See Kubernetes Worker Installation Overview.
Creating new Kubernetes clusters that use the Docker runtime is not supported.
Legacy Kubernetes clusters will be supported for a limited time after Hewlett Packard Enterprise provides a procedure to migrate from Docker to containerd. See Migrating Kubernetes Clusters from Docker to containerd.
Cluster Compatibility
If a deployment has been upgraded from an earlier version of HPE Ezmeral Runtime Enterprise with existing Kubernetes clusters, the deployment can have a mixture of legacy Kubernetes clusters and new containerd-based Kubernetes clusters. However, within a Kubernetes cluster, the same runtime (either containerd or Docker) is required.
The HPE Ezmeral Runtime Enterprise control plane hosts (Controller, Shadow Controller, Arbiter, and Gateway), are not part of a Kubernetes cluster. Control plane hosts use the Docker runtime and can manage both the new clusters and the legacy Kubernetes clusters in the same deployment.