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Storage

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Pods are disposable, but data usually isn't. This section builds the storage mental model in layers: the ephemeral volumes attached directly to a pod spec, the PersistentVolume/PersistentVolumeClaim abstraction that survives a pod being rescheduled, the StorageClasses that provision that storage on demand, and the patterns StatefulSets use to give each replica its own durable disk.

Kubernetes Storage at a Glance

Object What it is How long the data lasts Usually created by
Volume (emptyDir, hostPath, configMap, ...) Storage declared inside a pod spec emptyDir lives as long as the pod; hostPath stays on that one node The app team, in the pod spec
PersistentVolume (PV) A piece of real storage: a cloud disk, an NFS share, a local disk Independent of any pod An admin, or a StorageClass automatically
PersistentVolumeClaim (PVC) A request for storage: size, access mode, and class Until the claim is deleted; the PV's reclaimPolicy then decides whether the data is kept The app team
StorageClass A template that creates PVs on demand through a CSI driver Cluster-wide configuration The platform team

The everyday pattern for persistent storage is a PVC plus a pod that mounts it. The StorageClass creates the disk behind the claim:

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: data
spec:
  accessModes: ["ReadWriteOnce"]
  storageClassName: standard      # list the classes in your cluster: kubectl get storageclass
  resources:
    requests:
      storage: 10Gi
---
apiVersion: v1
kind: Pod
metadata:
  name: app
spec:
  containers:
    - name: app
      image: nginx:1.27
      volumeMounts:
        - name: data
          mountPath: /usr/share/nginx/html
  volumes:
    - name: data
      persistentVolumeClaim:
        claimName: data

Read in this order

  1. Volumes — ephemeral volume types (emptyDir, hostPath, configMap, secret, projected), and why none of them survive a pod being rescheduled to a different node
  2. PersistentVolumes and PersistentVolumeClaims — the PV/PVC lifecycle and binding, access modes, and reclaim policies
  3. StorageClasses and Dynamic Provisioning — CSI drivers, the dynamic provisioning flow end to end, and volume expansion
  4. StatefulSet Storage Patterns — volumeClaimTemplates, one PVC per replica, and what happens to that storage when pods and StatefulSets are deleted

If you only remember one thing

A Pod's volumes: block describes how storage is attached to that pod. It says nothing about where the bytes actually live or whether they outlive the pod — that's what PersistentVolumes, PersistentVolumeClaims, and StorageClasses are for.

Next

Once you can reason about how a pod gets durable storage, continue to Configuration and Packaging to see how the same workloads get their configuration and secrets injected.