Feature Overview

• Kubernetes offers different ways to consume, one could request persistent volumes that survive pod termination or ask for a ephemeral storage space that will be consumed during the lifetime of the pod.
• This feature tracks the improvements around ephemeral storage as some workloads rely on reliable temporary storage space such as batch jobs, caching services or any app that does not care whether the data is stored persistently across restarts

Goals

As described in the kubernetes "ephemeral volumes" documentation this features tracks GA and improvements in

• emptyDir: empty at Pod startup, with storage coming locally from the kubelet base directory (usually the root disk) or RAM
• CSI ephemeral volumes: similar to the previous volume kinds, but provided by special CSI drivers which specifically support this feature
• generic ephemeral volumes, which can be provided by all storage drivers that also support persistent volumes

OCPPLAN-9193 Implemented local ephemeral capacity management as well as CSI Generic ephemeral volume. This feature tracks the remaining work to GA CSI ephemeral in-inline volume, specially the admission plugin to make the feature secure and prevent any insecure driver from using it. Ephemeral in-line is required by some CSI as key feature to operate (e.g SecretStore CSI), ODF is also planning to GA ephemeral in-line with ceph CSI. 

Requirements

Use Cases

This Section:

• As an OCP user I want to consume ephemeral storage for my workload
• As an OCP user I would like to include my PV definition directly in my app definition
• As an OCP admin I would like to offer ephemeral volumes to my users though CSI
• As a partner I would like to onboard a driver that relies on CSI inline volumes

Customer Considerations

• Make sure each ephemeral volume option is clearly identified and documented for each purpose.

• Make sure we highlight ephemeral volume options that require a specific driver support