Use a custom StorageClass with your workloads

To define specific storage behaviors for your containerized workloads on Google Kubernetes Engine (GKE) on Azure, create and use custom StorageClasses. By customizing StorageClasses, you can optimize storage performance and cost for your applications by selecting different Azure disk types, file system types, and other parameters for your PersistentVolumes. This capability helps you run efficient services by tailoring storage to your workload's exact needs.

GKE on Azure automatically deploys and manages the Azure Disk CSI Driver and Azure File CSI Driver, which are essential for handling storage provisioning. The versions of these drivers are tied to your GKE on Azure Kubernetes version and update automatically with cluster upgrades, ensuring seamless compatibility for your custom StorageClasses.

Use a custom StorageClass

You can create additional StorageClasses for volumes or use Container Storage Interface (CSI) Drivers.

  1. Choose if you are using an Azure disk volume or another CSI driver.

    Azure Disk Volume

    You can create your own custom StorageClass that specifies an Azure Disk volume type, file system type, and other parameters. You can find additional StorageClass parameters on the GKE on Azure Azure Disk CSI Driver GitHub page.

    To configure a custom StorageClass, copy the following YAML manifest into a file named my-custom-class.yaml.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: CLASS_NAME
provisioner: disk.csi.azure.com
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true

    Replace CLASS_NAME with the name of your new StorageClass.

    For example, the following YAML creates a new StorageClass that provisions volumes in a specific storage account and applies a tag of group=dev to each new volume.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: my-custom-class
provisioner: disk.csi.azure.com
volumeBindingMode: WaitForFirstConsumer
allowVolumeExpansion: true
parameters:
 storageAccount: my-storage-account
 tags: group=dev

    CSI Driver

    You can specify a different CSI driver in the provisioner field.

    To create a StorageClass with another CSI driver, you can use the following example YAML.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: CLASS_NAME
provisioner: CSI_DRIVER_NAME
volumeBindingMode: WaitForFirstConsumer
parameters:
 ...

    Replace the following values:

    • CLASS_NAME: the name of the StorageClass (for example, my-custom-class).
    • CSI_DRIVER_NAME: the name of the CSI driver (for example, csi.example.com).

    Next, configure subfields under parameters according to your CSI driver's documentation.

  2. Apply the YAML to your cluster.

    kubectl apply -f my-custom-class.yaml

  3. Create a PersistentVolumeClaim with a custom StorageClass.

    After you create a custom StorageClass, you can specify it in a PVC. The following example creates a PVC named my-pvc that references the StorageClass my-custom-class.

    apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: my-pvc
spec:
 accessModes:
  - ReadWriteOnce
 resources:
  requests:
   storage: 30Gi
 storageclassName: my-custom-class

Set the default StorageClass

GKE on Azure uses a default StorageClass called standard-rwo that provisions standard SSD Azure disks with LRS. You can change the default to another StorageClass.

To change the default StorageClass:

  1. Update the is-default-class annotation for the standard-rwo StorageClass with kubectl patch.

    kubectl patch storageclass standard-rwo -p \
 '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"false"}}}'

  2. Create a new StorageClass that has the annotation storageclass.kubernetes.io/is-default-class: true.

    The following example StorageClass uses the disk.csi.azure.com driver. To install another storage driver, see Installing a CSI driver.

    Copy the following YAML into a file named my-custom-class.yaml.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: CLASS_NAME
 annotations:
  storageclass.kubernetes.io/is-default-class: true
provisioner: disk.csi.azure.com
volumeBindingMode: WaitForFirstConsumer
parameters:
 skuName: VOLUME_TYPE

    Replace the following:

    • CLASS_NAME: the name of your new StorageClass.
    • VOLUME_TYPE: the Azure Disk volume type that the StorageClass creates.

    For example, the following YAML creates a new default StorageClass that provisions Premium SSD Azure Disk volumes.

    apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
 name: my-custom-default-class
 annotations:
  storageclass.kubernetes.io/is-default-class: "true"
provisioner: disk.csi.azure.com
volumeBindingMode: WaitForFirstConsumer
parameters:
 skuName: Premium_LRS

  3. Apply the new custom class to your cluster.

    kubectl apply -f my-custom-class.yaml

After applying this manifest, GKE on Azure uses the my-custom-default-class StorageClass for new storage requests.

Reference the StorageClass in a StatefulSet

To use your new StorageClass, you can reference it in a StatefulSet's volumeClaimTemplates.

When you reference a StorageClass in a StatefulSet's volumeClaimTemplates specification, Kubernetes provides stable storage using PersistentVolumes (PVs). Kubernetes calls the provisioner defined in the StorageClass to create a new storage volume. After the volume is provisioned, Kubernetes automatically creates a PV.

The following StatefulSet references the my-custom-class StorageClass and provisions a 1 gibibyte volume:

apiVersion: apps/v1
kind: StatefulSet
metadata:
  name: web
spec:
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: registry.k8s.io/nginx-slim:0.8
        volumeMounts:
        - name: www
          mountPath: /usr/share/nginx/html
  volumeClaimTemplates: # This is the specification in which you reference the StorageClass
  - metadata:
      name: www
    spec:
      accessModes: [ "ReadWriteOnce" ]
      resources:
        requests:
          storage: 1Gi
      storageClassName: my-custom-class # This field references the existing StorageClass

What's next