How to Integrate Kubernetes with External Storage Using CSI (Local Mode Guide)

Background

In the cloud‑native era, Kubernetes is the de‑facto standard for container orchestration, but containers are short‑lived while data must be persisted. This article explains how to integrate Kubernetes with powerful external storage to keep data safe, reliable and easy to manage.

Background

The workload relies on CPU, memory, network and storage. CPU and memory are virtualized for containers; network is provided by a CNI plugin (Calico); storage (CSI) is introduced in this article.

CSI Overview

The Container Storage Interface (CSI) is an abstraction that allows Kubernetes to work with many storage systems. Five integration methods are covered:

Local mode storage

Kubernetes with NFS

Kubernetes with RBD

Kubernetes with CephFS

Kubernetes with Ceph RGW

Local Mode Storage

Local mode uses hostPath as storage. It automatically schedules pods onto the node where the PersistentVolume resides, eliminating the need to specify a node in the Deployment.

Tip: If a node fails, pods using local storage cannot start.

Step 1 – Create a StorageClass

cat <<EOF | kubectl apply -f -
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: local-storage
provisioner: kubernetes.io/no-provisioner
volumeBindingMode: WaitForFirstConsumer
EOF

Step 2 – Create a PersistentVolume

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: PersistentVolume
metadata:
  name: test
spec:
  capacity:
    storage: 10Gi
  volumeMode: Filesystem
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Delete
  storageClassName: local-storage
  local:
    path: /data/test-local-pv
  nodeAffinity:
    required:
      nodeSelectorTerms:
      - matchExpressions:
        - key: kubernetes.io/hostname
          operator: In
          values:
          - k8s-node01
EOF

Step 3 – Create a PersistentVolumeClaim

cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: test-local-pvc
  namespace: default
spec:
  storageClassName: local-storage
  volumeMode: Filesystem
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 10G
EOF

Tip: In local mode, the PV and PVC are not bound immediately; binding occurs only when a pod consumes the PVC because the StorageClass’s volumeBindingMode must be WaitForFirstConsumer.

Verification

Deploy a workload and mount the volume

cat <<EOF | kubectl apply -f -
apiVersion: apps/v1
kind: Deployment
metadata:
  name: tools
spec:
  replicas: 1
  selector:
    matchLabels:
      app: tools
  template:
    metadata:
      labels:
        app: tools
    spec:
      containers:
      - name: tools
        image: registry.cn-guangzhou.aliyuncs.com/jiaxzeng6918/tools:v1.1
        volumeMounts:
        - name: data
          mountPath: /data
      volumes:
      - name: data
        persistentVolumeClaim:
          claimName: test-local-pvc
EOF

Check the pod’s node

kubectl get pod -o wide

Confirm the mount

kubectl exec -it tools-6f6f7cd4bf-jjlbg -- df -h /data

Tip: Local mode cannot enforce storage size limits.

Conclusion

Integrating Kubernetes with external storage expands the storage capabilities of containerized applications and provides flexible, efficient data management. As cloud‑native technologies evolve, more storage solutions will seamlessly integrate with Kubernetes, unlocking data’s potential to drive business innovation.