We are trying to create a solution where we want to replicate changes made to a folder inside any of the pods of the Statefulset. Any file changes inside that folder on any POD should also reflect in other pods. Is there a sidecar solution for this requirement? Because we know that Statefulset will create separate PVs for each POD and there won’t be any common mount across the pods of the Statefulset.

>Solution :

You can try using the NFS or file system like EFS using that you will be able to implement the ReadWritemany.

For ref Azure File.

apiVersion: apps/v1beta1
kind: StatefulSet
metadata:
  name: statefulset-azurefile
  labels:
    k8s-app: nginx
    version: v1
spec:
  serviceName: statefulset-azurefile
  replicas: 1
  template:
    metadata:
      labels:
        k8s-app: nginx
        version: v1
    spec:
      containers:
      - name: statefulset-azurefile
        image: nginx
        volumeMounts:
        - name: persistent-storage
          mountPath: /mnt/azurefile
  volumeClaimTemplates:
  - metadata:
      name: persistent-storage
      annotations:
        volume.beta.kubernetes.io/storage-class: azurefile
    spec:
      accessModes: [ "ReadWriteMany" ]
      resources:
        requests:
          storage: 5Gi

Demo : https://github.com/andyzhangx/demo/tree/master/linux/statefulset

If volumeClaimTemplates not work as expected use the persistentVolumeClaim

Article to read about ReadWriteMany access Mode :https://docs.microsoft.com/en-us/azure/aks/azure-files-volume

If you are on other cloud providers like GCP, AWS, Oracle(OCI) provides different file services.

• GCP- Filestore
• AWS- EFS
• OCI- Filestorage

OCI article if you want to explore : https://enabling-cloud.github.io/oci-learning/manual/StaticPersistentVolumeOnOCI.html