The Claim Check System

If a Persistent Volume (PV) is a physical hard drive in the data center, a Persistent Volume Claim (PVC) is the "ticket" a user presents to get access to it.

1. The Separation of Concerns

Kubernetes splits storage responsibilities into two roles:

Cluster Administrator: Manages the infrastructure. Creates the PVs (the actual storage).
Developer: Deploys applications. Creates a PVC (a request for storage).

The Developer doesn’t care if the storage is on AWS EBS, Google PD, or a NetApp filer. They just say: “I need 10Gi of ReadWriteOnce storage.” The cluster handles the matchmaking.

2. The Binding Lifecycle

The process of matching a PVC to a PV is called Binding.

Pending: The PVC is created but hasn’t found a matching PV.
Bound: The Control Plane finds a PV that satisfies the PVC’s requirements (Size, AccessMode, StorageClass) and glues them together.
Released: The PVC is deleted, and the PV is released (depending on ReclaimPolicy).

3. Interactive: Binding Simulator

Watch how the Kubernetes Control Plane matches a user’s request (PVC) to available infrastructure (PVs).

Infrastructure (PVs)

PV-1

Size: 5Gi Mode: RWO

PV-2

Size: 20Gi Mode: RWO

PV-3

Size: 10Gi Mode: RWX

User Request (PVC)

my-claim

Needed: 10Gi Mode: RWO

PENDING

$ Waiting for PVC creation...

4. Access Modes Matrix

The Access Mode determines how the storage can be mounted. This is a capability of the physical storage provider.

Mode	Abbreviation	Description	Typical Use
ReadWriteOnce	RWO	Mounted by Single Node as Read-Write.	Databases (Postgres, MySQL). Block Storage.
ReadWriteMany	RWX	Mounted by Many Nodes as Read-Write.	Web Assets, Shared Logs. NFS / EFS.
ReadOnlyMany	ROX	Mounted by Many Nodes as Read-Only.	Config Data, AI Models.

[!WARNING] RWO is per NODE, not per POD. If you have 3 Replicas of a Pod scheduled on the same Node, they can ALL access the RWO volume. But if one Pod moves to Node 2, it loses access.

5. Using a PVC in a Pod

To use the storage, the Pod refers to the PVC by name. The Pod never talks to the PV directly.

PVC YAML

Pod YAML

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: mysql-pv-claim
spec:
  accessModes:
  - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  # Leave empty to find any matching PV, or specify storageClassName
  storageClassName: ""

apiVersion: v1
kind: Pod
metadata:
  name: mysql-pod
spec:
  containers:
  - name: mysql
  image: mysql:5.7
  volumeMounts:
  - mountPath: "/var/lib/mysql"
    name: mysql-storage
  volumes:
  - name: mysql-storage
    persistentVolumeClaim:
      claimName: mysql-pv-claim

6. The Problem with Manual PVs

In this model, the Administrator must manually create PVs before Developers can claim them. If the Admin sleeps, development stops.

To solve this scaling bottleneck, Kubernetes introduced Storage Classes and Dynamic Provisioning.

Persistent Volume Claims (PVC)