Better document supported access modes

[da-amit-mujawar]

/kind bug

What happened?
When we try to use ReadOnlyMany, the volume attachment fails with error
1 controller.go:637] "isValidCapability: access mode is not supported" accessMode="MULTI_NODE_READER_ONLY"

What you expected to happen?
Should have worked and mounted the volume in the Pod.
Question: Which modes are supported by this driver? I cannot find a documentation as to which modes are supported and which are not.

How to reproduce it (as minimally and precisely as possible)?

Anything else we need to know?:
The only mode that worked in EKS was ReadWriteOnce. As a work around we set the volume as readonly: true inside the Pod.

Environment

• Kubernetes version (use kubectl version):
• Driver version:

[ConnorJC3]

Hi, ReadOnlyMany support is not available in the EBS CSI Driver. This is because the only multi-node volume supported by the EBS CSI Driver is ReadWriteMany on block devices for EBS Multi-Attach volumes (useful for some niche usecases such as clustered filesystems and software with specific support. EBS is unable to mount a block device read only, so we cannot support ReadOnlyMany block devices.

I will leave this issue open as a documentation issue for us to better document these limitations.

/retitle Better document supported access modes