OpenShift

Ondat V2 supports Openshift v4.

OpenShift and Ondat communicate with each other to perform actions such as creation, deletion and mounting of volumes through CSI. The CSI container running in the Ondat Daemonset creates a Linux socket that allows the communication between OpenShift and Ondat

Installation

Ondat v2 supports OpenShift 4.0, 4.1, 4.2, 4.3, 4.4 and 4.5.

To install Ondat on OpenShift, please follow our installation instructions page.

N.B. Openshift 4 uses the CRI-O container runtime that sets a default PID limit of 1024. Ondat recommends that the limit be raised to 32768. Please see our prerequisites for more details.

OpenShift Upgrades

OpenShift provides an upgrade operator that automates the process of orchestrator version changes.

This procedure can cause Ondat to malfunction due to sequential node restarts not taking the presence of stateful application data into consideration. To avoid this issue, make sure all stateful workloads using Ondat Volumes are stopped - usually by scaling StatefulSets to 0. Please contact Ondat support for further advice if required.

OpenShift requires the internal registry to be available during the upgrade, however Ondat volumes may not be available. Therefore using Ondat for the internal registry is not recommended.

CSI (Container Storage Interface) Note

CSI is the standard that enables storage drivers to release on their own schedule. This allows storage vendors to upgrade, update, and enhance their drivers without the need to update Kubernetes source code, or follow Kubernetes release cycles. Ondat v2 uses CSI to implement communication with the OpenShift controlplane.

Ondat PersistentVolumeClaims

The user can provide standard PVC definitions and Ondat will dynamically provision them. Ondat presents volumes to containers with standard POSIX mount targets. This enables the Kubelet to mount Ondat volumes using standard linux device files. Checkout device presentation for more details.