Sign In

Curriculum 17: Storage & Volumes

Storage Classes

12 min · 25 XP

Storage Classes

A StorageClass enables dynamic provisioning of PersistentVolumes. Instead of an administrator manually creating PVs, the StorageClass automatically provisions storage when a PVC is created.

Defining a StorageClass

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: fast-ssd
  annotations:
    storageclass.kubernetes.io/is-default-class: "true"
provisioner: kubernetes.io/aws-ebs
parameters:
  type: gp3
  fsType: ext4
reclaimPolicy: Delete
volumeBindingMode: WaitForFirstConsumer

kubectl apply -f storageclass.yaml
kubectl get storageclass

Default Storage Class

A cluster can have one default StorageClass. PVCs that do not specify a storageClassName automatically use the default class.

# View storage classes and identify the default
kubectl get sc

# The default class is marked with "(default)" in the output

Using a StorageClass in a PVC

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: dynamic-claim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 20Gi
  storageClassName: fast-ssd

When this PVC is created, the fast-ssd StorageClass provisions a new PV automatically.

Common Provisioners

Different environments use different provisioners:

# List all storage classes with their provisioners
kubectl get sc -o custom-columns=NAME:.metadata.name,PROVISIONER:.provisioner

Popular provisioners include kubernetes.io/aws-ebs for AWS, kubernetes.io/gce-pd for GCP, kubernetes.io/azure-disk for Azure, and rancher.io/local-path for local development clusters.

Volume Binding Modes

  • Immediate -- provisions storage as soon as the PVC is created
  • WaitForFirstConsumer -- delays provisioning until a pod using the PVC is scheduled, ensuring the volume is created in the correct availability zone