Kubernetes Storage (PV, PVC, and StorageClass)

Decoupling storage implementation from application requirements in Kubernetes.

Edit Concept ✏️

Kubernetes Storage

Kubernetes uses a set of abstractions to manage persistent storage, allowing developers to request storage without knowing the details of the underlying infrastructure (e.g., AWS EBS, GCP PD, or local disks).

1. PersistentVolume (PV)

  • Definition: A piece of storage in the cluster that has been provisioned by an administrator or dynamically provisioned using a StorageClass.
  • Scope: It is a cluster-level resource (like a Node) and is not tied to a specific namespace.
  • Lifecycle: It has a lifecycle independent of any individual Pod that uses it.

2. PersistentVolumeClaim (PVC)

  • Definition: A request for storage by a user.
  • Scope: It is a namespace-level resource.
  • Function: Just as a Pod consumes Node resources (CPU/Memory), a PVC consumes PV resources (Size/Access Modes).
  • Binding: Kubernetes looks for a PV that matches the PVC’s requirements and “binds” them together.

3. StorageClass

  • Definition: A way for administrators to describe the “classes” of storage they offer (e.g., “fast-ssd”, “slow-hdd”).
  • Dynamic Provisioning: Allows PVs to be created on-demand when a PVC is created, rather than having an admin manually create PVs in advance.

4. Access Modes

  • ReadWriteOnce (RWO): Mounted as read-write by a single node.
  • ReadOnlyMany (ROX): Mounted as read-only by many nodes.
  • ReadWriteMany (RWX): Mounted as read-write by many nodes (requires network storage like NFS).