Storage

Storage classes, PersistentVolumes, and PersistentVolumeClaims

Overview

Kubernetes provides an abstraction for storage that enables decoupling storage from Pod lifecycle. This section covers storage concepts: StorageClasses, PersistentVolumes (PV), and PersistentVolumeClaims (PVC).

Storage Hierarchy

StorageClass (Storage Profile)
    ↓
PersistentVolume (Cluster Resource)
    ↓
PersistentVolumeClaim (User Request)
    ↓
Pod (Uses PVC)

Study Path

1. Storage Concepts - Understanding PV, PVC, StorageClass
2. Storage Classes - Storage profiles and provisioning
3. Persistent Volumes - Cluster storage resources
4. Persistent Volume Claims - User storage requests

Storage Comparison

Type	Scope	Lifecycle	Use Case
emptyDir	Pod	Deleted with pod	Temporary storage, shared data
hostPath	Node	Manual	Node access, testing
ConfigMap	Pod	Managed	Configuration files
Secret	Pod	Managed	Sensitive files
PVC	Namespace	Managed	Persistent data
PV	Cluster	Managed	Storage resources

Quick Reference

Common Commands

# StorageClasses
kubectl get storageclasses
kubectl describe storageclass fast-ssd

# PersistentVolumes
kubectl get pv
kubectl describe pv pv-001

# PersistentVolumeClaims
kubectl get pvc
kubectl describe pvc data-pvc
kubectl delete pvc data-pvc

Storage in Pod

apiVersion: v1
kind: Pod
metadata:
  name: storage-pod
spec:
  containers:
  - name: app
    image: nginx
    volumeMounts:
    - name: data-volume
      mountPath: /data
  volumes:
  - name: data-volume
    persistentVolumeClaim:
      claimName: data-pvc

Storage Modes

Access Mode	Description
ReadWriteOnce	Single node read-write (RWO)
ReadOnlyMany	Multiple nodes read-only (ROX)
ReadWriteMany	Multiple nodes read-write (RWX)
ReadWriteOncePod	Single pod read-write (RWX)

Reclaim Policies

Policy	Description
Retain	Manual reclamation, data preserved
Delete	Automatic deletion when PVC deleted
Recycle	Deprecated: Runs rm -rf on volume

Next Steps

1. Learn Storage Concepts: Storage Concepts
2. Understand Storage Classes: Storage Classes
3. Practice: Lab 04: Storage Labs

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Continue Learning:

• Storage Concepts
• Storage Classes

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