Storage Classes

In this lesson, we’ll explore how StorageClasses enable dynamic volume provisioning in Kubernetes. If you’re familiar with static provisioning—where you manually create cloud disks and bind them via PersistentVolumes (PVs) and PersistentVolumeClaims (PVCs)—you’ll see how StorageClasses automate this workflow.

Table of Contents

• Static Provisioning Recap
• Dynamic Provisioning with StorageClass
• StorageClass Definition
• Using a Dynamic PVC and Pod
• Comparing Provisioning Methods
• Customizing StorageClass Parameters
• Defining Service Tiers
• Links and References

Static Provisioning Recap

With static provisioning, you manually create the underlying cloud disk before you define a PV:

gcloud beta compute disks create \
  --size=1GB \
  --region=us-east1 \
  pd-disk

Then you define:

# pv-definition.yaml
apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-vol1
spec:
  capacity:
    storage: 500Mi
  accessModes:
    - ReadWriteOnce
  gcePersistentDisk:
    pdName: pd-disk
    fsType: ext4

# pvc-definition.yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: myclaim
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 500Mi

# pod-definition.yaml
apiVersion: v1
kind: Pod
metadata:
  name: random-number-generator
spec:
  containers:
    - name: alpine
      image: alpine
      command: ["/bin/sh", "-c"]
      args:
        - shuf -i 0-100 -n 1 >> /opt/number.out
      volumeMounts:
        - name: data-volume
          mountPath: /opt
  volumes:
    - name: data-volume
      persistentVolumeClaim:
        claimName: myclaim

Dynamic Provisioning with StorageClass

With a StorageClass, Kubernetes can automatically create and bind a PV when you apply a PVC. This dynamic provisioning eliminates manual disk creation.

StorageClass Definition

Define a StorageClass that uses the GCE PD provisioner:

# sc-definition.yaml
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: google-storage
provisioner: kubernetes.io/gce-pd

Using a Dynamic PVC and Pod

1. Create a PVC that references your StorageClass:

   # pvc-dynamic.yaml
   apiVersion: v1
   kind: PersistentVolumeClaim
   metadata:
     name: myclaim
   spec:
     storageClassName: google-storage
     accessModes:
       - ReadWriteOnce
     resources:
       requests:
         storage: 500Mi
   

2. Deploy a Pod that mounts the PVC:

   # pod-dynamic.yaml
   apiVersion: v1
   kind: Pod
   metadata:
     name: random-number-generator
   spec:
     containers:
       - name: alpine
         image: alpine
         command: ["/bin/sh", "-c"]
         args:
           - shuf -i 0-100 -n 1 >> /opt/output.txt
         volumeMounts:
           - name: data-volume
             mountPath: /opt
     volumes:
       - name: data-volume
         persistentVolumeClaim:
           claimName: myclaim
   

Kubernetes will then:

1. Provision a new GCE PD of the requested size.
2. Create a corresponding PV.
3. Bind your PVC to that PV.
4. Attach the volume to your Pod.

Comparing Provisioning Methods

Customizing StorageClass Parameters

Most provisioners let you fine-tune disks. For GCE PD, you can specify:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: google-storage
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-standard        # pd-standard or pd-ssd
  replication-type: none   # none or regional-pd

Defining Service Tiers

You can create multiple StorageClasses to represent different performance tiers:

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: silver
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-standard
  replication-type: none
---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: gold
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-ssd
  replication-type: none
---
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: platinum
provisioner: kubernetes.io/gce-pd
parameters:
  type: pd-ssd
  replication-type: regional-pd

When you create a PVC, just set storageClassName to select your tier. Kubernetes handles provisioning and binding behind the scenes.

Links and References

• Kubernetes StorageClass Documentation
• Persistent Volumes
• GCE PD Provisioner
• gcloud compute disks create

Mastering StorageClasses empowers you to build scalable, self-service storage in your Kubernetes clusters—no more manual volume management!