CODEWITHSUNDEEP
kubernetesdigital-oceankubernetes-pod
FrancisV
FrancisV

Reputation: 1709

Kubernetes "shared" persistent volume on DigitalOcean

I have a persistent volume defined as

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: ghost-cms-content
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  storageClassName: do-block-storage

and a deployment defined as

---
kind: Deployment
apiVersion: apps/v1
metadata:
  name: ghost-cms
spec:
  replicas: 4
  strategy:
    type: RollingUpdate
    rollingUpdate:
      maxSurge: 1
      maxUnavailable: 1
  selector:
    matchLabels:
      app: ghost-cms
      tier: frontend
  template:
    metadata:
      labels:
        app: ghost-cms
        tier: frontend
    spec:
      topologySpreadConstraints:
        - maxSkew: 1
          topologyKey: topology.kubernetes.io/region
          whenUnsatisfiable: ScheduleAnyway
          labelSelector:
            matchLabels:
              app: ghost-cms
              tier: frontend
      containers:
        - name: ghost-cms
          image: ghost:4.6-alpine
          imagePullPolicy: Always
          ports:
            - containerPort: 2368
          volumeMounts:
            - mountPath: /var/lib/ghost/content
              name: content
          env:
            - name: url
              value: https://ghost.site
          resources:
            requests:
              cpu: 100m
              memory: 128Mi
            limits:
              cpu: 250m
              memory: 256Mi
      volumes:
        - name: content
          persistentVolumeClaim:
            claimName: ghost-cms-content

but each replica appears to have a unique volume that is not shared with the rest of the replicas. For instance, when I create a text file inside /var/lib/ghost/content in one of the pods, I don't see it in the volume of the other pods. What am I doing wrong?

Upvotes: 3

Views: 2454

Answers (1)

Harsh Manvar
Harsh Manvar

Reputation: 30083

PVC with permission

accessModes:
  - ReadWriteOnce

Each pod will get the one volume or PVC, as it's readwrite once.

If you want to keep shared volume across replicas you can use the NFS with accessMode ReadWriteMany

 accessModes:
      - ReadWriteMany

Read more at : https://kubernetes.io/docs/concepts/storage/persistent-volumes/#access-modes

Example : https://medium.com/asl19-developers/create-readwritemany-persistentvolumeclaims-on-your-kubernetes-cluster-3a8db51f98e3

You can also use Minio, GlusterFS to creeat the NFS or any managed service like GCP filestore providing NFS and attach that to POD.

GKE example : https://medium.com/@Sushil_Kumar/readwritemany-persistent-volumes-in-google-kubernetes-engine-a0b93e203180

Upvotes: 4

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