Re-use PersistentVolume after re-installing a helm deployment

Question

When I helm delete <deploymentname> a deployment its PVs and PVCs are deleted as well. How can I avoid the actual data in the PVs from being deleted and be able to reclaim those PVs when I helm install <deploymentname> again?

I am using helm upgrade regularly but it makes me very uncomfortable if all it takes to delete all data is a helm delete (even without --purge option it removes all PVs)

Answer 1

If you are looking for persistence between deletion and re-creation, you should not use Deployment but StatefulSet. Stateful sets are something designed to be used for deploying "database-like" applications.

Stateful sets use persistent pod naming and support generating pvc per pod, also with persistent name. Those pvcs are not deleted when pods/stateful sets are deleted so they remain for reuse by recreated stateful sets or manual release by deleting the pvc(s).

Example StatefulSet took from https://kubernetes.io/docs/tutorials/stateful-application/basic-stateful-set/ is attached below.

apiVersion: v1
kind: Service
metadata:
  name: nginx
  labels:
    app: nginx
spec:
  ports:
  - port: 80
    name: web
  clusterIP: None
  selector:
    app: nginx
---
apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  serviceName: "nginx"
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: k8s.gcr.io/nginx-slim:0.8
        ports:
        - containerPort: 80
          name: web
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates:
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 1Gi