9.4: PersistentVolume (PV) with NFS

https://drive.google.com/file/d/1lCwC8hfi6bfx5-m4wwuS3NCtd31FjYct/view?usp=sharing

🔍 YAML Breakdown

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pvone-nfs
spec:
  capacity:
    storage: 5Gi                 # ← Total storage size
  volumeMode: Filesystem         # ← Standard filesystem (not block)
  accessModes:
    - ReadWriteOnce              # ← RWO: one node at a time
  persistentVolumeReclaimPolicy: Recycle  # ← What to do when PVC is deleted
  storageClassName: slow         # ← Links to StorageClass (optional)
  nfs:
    path: /foldername            # ← Exported directory on NFS server
    server: ip-address-nfs-server # ← NFS server IP/DNS

🔑 Key Insight:

This PV represents 5Gi of shared storage on an NFS server, accessible to any Pod in the cluster (as long as it’s on a node that can reach the NFS server).

💡 Why NFS?

Shared storage: Multiple Pods can access the same data (with proper accessModes)

Multi-node safe: Data isn’t tied to a specific k3s node

Cheap & simple: Runs on any Linux server

📌 Critical Concepts Explained

1. `accessModes`

Mode	Meaning	NFS Support
`ReadWriteOnce` (RWO)	Read-write by one node	✅ Yes
`ReadOnlyMany` (ROX)	Read-only by many nodes	✅ Yes
`ReadWriteMany` (RWX)	Read-write by many nodes	✅ Yes! (NFS’s superpower)

⚠️ Your PV uses ReadWriteOnce → but NFS supports ReadWriteMany!

✅ For shared storage (e.g., web servers), use ReadWriteMany.

2. `persistentVolumeReclaimPolicy`

Policy	Behavior
`Retain`	Keep PV + data (manual cleanup)
`Delete`	Delete PV + data (cloud disks)
`Recycle`	Deprecated! Runs `rm -rf` (unsafe)

🚨 Critical Warning:

Recycle is deprecated since Kubernetes 1.11!

✅ Use Retain (for NFS) or Delete (for cloud).

3. `storageClassName`

Links PV to a StorageClass (for dynamic provisioning)
If not set, PV is statically provisioned (your case)

🧪 k3s Lab: Test NFS PersistentVolume

💡 Don’t have an NFS server?

We’ll use a k3s node as NFS server (for lab purposes).

🔍 YAML Breakdown

📌 Critical Concepts Explained

1. accessModes

2. persistentVolumeReclaimPolicy

3. storageClassName

🧪 k3s Lab: Test NFS PersistentVolume

🔧 Step 1: Set Up NFS Server (On a k3s Node)

1. `accessModes`

2. `persistentVolumeReclaimPolicy`

3. `storageClassName`