Migration from in-tree to CSI storage plugins and differences between both

Issue

• At the time when this KCS solution is being written, Kubernetes is working to migrate its current in-tree storage plugins to CSI. What is the reason of that?

  • Note: this is an upstream change which will arrive onto OpenShift.

• Will this migration be transparent for OpenShift users? Is there any action needed from OpenShift cluster administrators?

• Two different StorageClasses currently show up on OpenShift clusters for the storage platforms involved. See AWS example. Why? Which one is recommended to be used for PersistentVolumes?

  • Clarification: this statement is only applicable to the OpenShift versions released before the end of the migration, whose final stage will imply the removal of in-tree plugins as explained below.