Persistent Storage

Containers are ephemeral — when a pod restarts, its filesystem is lost. Persistent storage decouples data from the container lifecycle. This lesson covers PersistentVolumes, PersistentVolumeClaims, StorageClasses, CSI drivers, and backup strategies.

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The Storage Stack

┌──────────────────────────────────────┐
│          Pod                         │
│  ┌──────────────────────────────┐    │
│  │   Container                  │    │
│  │   volumeMount: /data         │    │
│  └──────────────┬───────────────┘    │
└─────────────────┼────────────────────┘
                  │
┌─────────────────▼────────────────────┐
│  PersistentVolumeClaim (PVC)         │
│  "I need 50Gi of fast SSD storage"   │
└─────────────────┬────────────────────┘
                  │  binds to
┌─────────────────▼────────────────────┐
│  PersistentVolume (PV)               │
│  "50Gi SSD volume, provisioned"      │
└─────────────────┬────────────────────┘
                  │  backed by
┌─────────────────▼────────────────────┐
│  StorageClass                        │
│  "gp3-ssd" → CSI Driver → Cloud API │
└──────────────────────────────────────┘

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PersistentVolumes and PersistentVolumeClaims

PersistentVolume (PV)

A PV represents a piece of storage in the cluster, provisioned by an administrator or dynamically via a StorageClass.

apiVersion: v1
kind: PersistentVolume
metadata:
  name: database-pv
spec:
  capacity:
    storage: 100Gi
  accessModes:
    - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: fast-ssd
  csi:
    driver: ebs.csi.aws.com
    volumeHandle: vol-0abc123def456789

PersistentVolumeClaim (PVC)

A PVC is a request for storage by a user.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: postgres-data
spec:
  accessModes:
    - ReadWriteOnce
  storageClassName: fast-ssd
  resources:
    requests:
      storage: 50Gi