Kubernetes Storage Classes

Introduction

In Kubernetes, Storage Classes provide a way to define different types of storage that can be dynamically provisioned. They specify the parameters for creating persistent storage volumes, enabling users to request storage with specific characteristics.

Key Concepts

What is a Storage Class?

A Storage Class is a Kubernetes resource that allows administrators to describe the "classes" of storage they offer. This includes details like the provisioner type, parameters, and reclaim policies.

Provisioners

Provisioners are responsible for creating the storage. Kubernetes supports multiple provisioners, including cloud providers like AWS, GCP, and Azure, as well as open-source solutions.

Reclaim Policy

The reclaim policy determines what happens to the persistent volume (PV) when the associated persistent volume claim (PVC) is deleted. Common policies include Retain, Delete, and Recycle.

Creating Storage Classes

To create a Storage Class, you need to define it in a YAML file. Below is a sample configuration:


apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: my-storage-class
provisioner: kubernetes.io/aws-ebs
parameters:
  type: gp2
  fsType: ext4
reclaimPolicy: Delete
allowVolumeExpansion: true

Use the following command to create the Storage Class:


kubectl apply -f my-storage-class.yaml

Using Storage Classes

To utilize a Storage Class, create a Persistent Volume Claim (PVC) that specifies the desired Storage Class:


apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  storageClassName: my-storage-class

Apply the PVC using the command:


kubectl apply -f my-pvc.yaml

Best Practices

Define clear naming conventions for Storage Classes.
Use reclaim policies thoughtfully to avoid data loss.
Document the parameters for each Storage Class for clarity.
Regularly review and update Storage Classes as necessary.
Test storage features before deploying in production.

FAQ

What is the difference between a PVC and a Storage Class?

A Persistent Volume Claim (PVC) is a request for storage by a user, while a Storage Class is a way to define the types of storage available for dynamic provisioning.

Can I change the Storage Class of an existing PVC?

No, once a PVC is bound to a PV, you cannot change its Storage Class. You would need to create a new PVC with the desired Storage Class.

How do I view existing Storage Classes?

You can list all Storage Classes using the command: kubectl get storageclass.