Course outline

01 · Kubernetes Architecture Deep Dive

02 · Workloads & Scheduling

03 · Networking, Storage & Service Mesh

04 · Platform Engineering & Multi-Tenancy

05 · Networking & Service Mesh

06 · Observability & Autoscaling

07 · Configuration & Secrets Management

08 · Stateful Storage Operations

09 · Security, Identity & Admission

10 · Release Packaging with Helm & Kustomize

11 · Operators, CRDs & Controllers

12 · Production Troubleshooting & Operations

Stage 5 · Platform

Stateful Storage Operations

PV & PVC Lifecycle

Binding, reclaim policies, access modes, volume expansion, and finalizer behavior.

7 min readKubernetes & Cloud NativePlatform

PV and PVC Overview

PersistentVolumes (PV) represent storage resources. PersistentVolumeClaims (PVC) are requests for storage. PVs are cluster-scoped; PVCs are namespace-scoped. PVCs bind to PVs based on capacity, access modes, and storage class.

Resource	Scope	Purpose
PV	Cluster	Represents physical storage
PVC	Namespace	Request for storage by a pod
StorageClass	Cluster	Defines storage provisioner and parameters

Binding Process

When a PVC is created, Kubernetes looks for a PV that satisfies the claim: sufficient capacity, matching access modes, and matching StorageClass. If found, the PV and PVC are bound. If not, the PVC stays Pending until a suitable PV appears.

PV and PVC binding


apiVersion: v1
kind: PersistentVolume
metadata:
  name: manual-pv
spec:
  capacity:
    storage: 10Gi
  accessModes:
  - ReadWriteOnce
  persistentVolumeReclaimPolicy: Retain
  storageClassName: manual
  hostPath:
    path: /mnt/data
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-claim
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  storageClassName: manual

The PVC requests 5Gi. The PV has 10Gi. They bind because the PV has enough capacity. The access modes must match. The StorageClass must match (or both must be empty string).

Reclaim Policies

ReclaimPolicy determines what happens to the PV when the PVC is deleted. Delete removes the volume from storage. Retain keeps the volume but disconnects it. Recycle (deprecated) clears the volume for reuse.

Reclaim policy behavior


Delete:
  PVC deleted -> PV deleted -> Volume deleted from storage
  (Data lost — use only for ephemeral data)

Retain:
  PVC deleted -> PV released -> Manual intervention required
  (Data preserved — admin must reattach or delete)

Recycle (deprecated):
  PVC deleted -> Volume cleared (rm -rf /thevolume/*)
  PV available for new claims

Retain is the safest policy. The PV enters Released state after the PVC is deleted. An admin must manually back up data, reattach the PV to a new PVC, or delete the PV. Delete is only safe for disposable data.

Access Modes

Access modes define how a volume can be mounted. ReadWriteOnce (RWO) allows single-node read/write. ReadOnlyMany (ROX) allows multi-node read-only. ReadWriteMany (RWX) allows multi-node read/write. ReadWriteOncePod (RWOP) allows single-pod read/write.

Mode	Abbreviation	Support
ReadWriteOnce	RWO	Most block storage (EBS, PD, Azure Disk)
ReadOnlyMany	ROX	NFS, CephFS, object storage
ReadWriteMany	RWX	NFS, CephFS, Azure Files
ReadWriteOncePod	RWOP	CSI drivers with RWOP support

Volume Expansion

Volume expansion grows a PVC without deleting it. The StorageClass must allow expansion (allowVolumeExpansion: true). Expansion works online (while mounted) or offline (while detached) depending on the CSI driver.

Expand a PVC


apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: expanding-claim
spec:
  accessModes:
  - ReadWriteOnce
  storageClassName: expandable
  resources:
    requests:
      storage: 100Gi  # Changed from 50Gi

Update the storage request to the new size. Kubernetes calls the CSI driver to expand the volume. Online expansion happens while the volume is mounted. The PVC status shows Resizing, then Bound when complete.

Finalizer Behavior

PVs and PVCs use finalizers to prevent deletion while in use. PVCs have kubernetes.io/pvc-protection. PVs have kubernetes.io/pv-protection. These finalizers are removed only when the resource is no longer in use.

Check and remove finalizers


# Check PVC finalizers
kubectl get pvc my-claim -o yaml | grep finalizers

# If PVC is stuck in Terminating, check for finalizers
kubectl describe pvc my-claim

# Remove finalizer (only if safe)
kubectl patch pvc my-claim -p '{"metadata":{"finalizers":null}}'
kubectl patch pv my-pv -p '{"metadata":{"finalizers":null}}'

Finalizers prevent accidental deletion. A PVC with a finalizer cannot be deleted while a Pod is using it. If a PVC is stuck in Terminating, check if a finalizer is preventing deletion. Only remove finalizers after ensuring data safety.

Check PVC binding status

Use kubectl get pvc to see binding status. Bound means the PVC is ready. Pending means no matching PV exists. Lost means the PV was deleted. Use kubectl describe pvc for detailed binding information.

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