Storage in Kubernetes

Kubernetes provides flexible ways to persist data, from temporary in-Pod storage to persistent disks that survive Pod and node failure. You’ll most commonly use Volumes, PersistentVolumes (PVs), and PersistentVolumeClaims (PVCs) to manage storage in production.

Types of Storage

Kubernetes supports several storage mechanisms:

Type Description
emptyDir Temporary, pod-level storage. Deleted when Pod is gone.
hostPath Mounts a path on the host node. Avoid in production.
configMap / secret Used for injecting configs/secrets into containers.
persistentVolume Abstracts physical storage (EBS, NFS, GCE PD, etc.).
volumeClaimTemplate Used by StatefulSets to dynamically provision volumes.

Volumes

Basic volumes are attached to a Pod spec and live as long as the Pod.

volumes:
  - name: cache
    emptyDir: {}

Use emptyDir for scratch space or caching — not persistent data.

PersistentVolumes (PVs) and PersistentVolumeClaims (PVCs)

To persist data beyond the life of a Pod, use the PV + PVC model:

  • A PV is a piece of actual storage (disk, NFS, etc.)
  • A PVC is a user’s request for storage
  • Kubernetes binds them together dynamically

PVC Example

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: app-storage
spec:
  accessModes: ["ReadWriteOnce"]
  resources:
    requests:
      storage: 1Gi

Pod using the PVC

volumes:
  - name: app-data
    persistentVolumeClaim:
      claimName: app-storage

containers:
  - name: web
    volumeMounts:
      - name: app-data
        mountPath: /data

Volume Modes & Access

  • Volume Modes:
  • Filesystem (default): mounts as a directory

  • Block: exposes the raw device

  • Access Modes:

  • ReadWriteOnce: one node read/write
  • ReadOnlyMany: multiple nodes read-only
  • ReadWriteMany: shared read/write (NFS, etc.)

StorageClasses

A StorageClass defines how storage should be provisioned dynamically.

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: fast
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-ssd

The cluster admin defines StorageClasses; PVCs can request one by name.

storageClassName: fast

Dynamic vs Static Provisioning

  • Dynamic: PVC automatically provisions a volume using a StorageClass.
  • Static: Admin manually creates PVs, and users bind to them with matching PVCs.

Best Practices

  • Use ReadWriteOnce unless your workload requires multi-node access.
  • Leverage StorageClass for automated provisioning.
  • Clean up PVCs when no longer needed — they may retain bound disks.
  • Use StatefulSets if each Pod needs its own PVC.

Summary

Storage in Kubernetes is abstracted through PVs and PVCs for flexibility and portability. Whether your app is stateless or stateful, Kubernetes can handle your storage needs — just make sure to pick the right type of volume for the job.