How to run more than one numberOfInstances with storageClass

Please, answer some short questions which should help us to understand your problem / question better?

Which image of the operator are you using? postgres-operator-1.13.0.tgz
Where do you run it - cloud or metal? Kubernetes or OpenShift? Bare Metal K8s
Are you running Postgres Operator in production? no
Type of issue? question

I'm using https://github.com/zalando/postgres-operator/blob/master/manifests/complete-postgres-manifest.yaml yaml to deploy my cluster on Bare Metal K8s.

Kindly help me define volume and additionalVolumes in this yaml so that I can assign different storageClass to each instance. I eventually want to run numberOfInstances: 2 and want to use different location for each instance. Currently, if I use

volume:
    size: 1Gi
    storageClass: standard-external

it doesn't support more than one instance as PVCs are not ReadWriteMany enabled.

zalando / postgres-operator

How to run more than one numberOfInstances with storageClass #2766