How do I create a persistent volume claim with ReadWriteMany in GKE?

I agree that it's disappointing but it's a consequence of the use of persistent disk which does not permit attaching to multiple instances read-write.

I've had success with NFS and with the limitations you describe.

You could -- as you state -- use Gluster or similar too.

A more expensive albeit managed Google Cloud alternative is Cloud Filestore: https://cloud.google.com/filestore/docs/accessing-fileshares

Your questions suggests that you need NFS-like semantics but, if you don't, you may consider using Google Cloud Storage.

It's possible now with Cloud Filestore.

First create a Filestore instance.

gcloud filestore instances create nfs-server
    --project=[PROJECT_ID]
    --zone=us-central1-c
    --tier=STANDARD
    --file-share=name="vol1",capacity=1TB
    --network=name="default",reserved-ip-range="10.0.0.0/29"

Then create a persistent volume in GKE.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: fileserver
spec:
  capacity:
    storage: 1T
  accessModes:
  - ReadWriteMany
  nfs:
    path: /vol1
    server: [IP_ADDRESS]

[IP_ADDRESS] is available in filestore instance details.

You can now request a persistent volume claim.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: fileserver-claim
spec:
  accessModes:
  - ReadWriteMany
  storageClassName: "fileserver"
  resources:
    requests:
      storage: 100G

Finally, mount the volume in your pod.

apiVersion: v1
kind: Pod
metadata:
  name: my-pod
spec:
  containers:
  - name: my container
    image: nginx:latest
    volumeMounts:
    - mountPath: /workdir
      name: mypvc
  volumes:
  - name: mypvc
    persistentVolumeClaim:
      claimName: fileserver-claim
      readOnly: false

Solution is detailed here : https://cloud.google.com/filestore/docs/accessing-fileshares