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Storage Management

Objectives​

In this tutorial, you will learn how to manage persistent storage in your Managed Kubernetes cluster. Kubernetes uses the StorageClass concept to define the different types of available storage.

By the end of this guide, you will be able to:

  • Understand the different StorageClasses available.
  • Create a PersistentVolumeClaim (PVC) to request storage.
  • Mount this storage in your Pods.

Available StorageClasses​

Cloud Temple offers several storage classes (StorageClasses) to meet your various performance and use case requirements:

  1. ceph-block (default)

    • Access Mode : Block (ReadWriteOnce).
    • Replication Factor : X3 (high availability).
    • Use Case : This is the default class, ideal for databases and applications requiring exclusive and high-performance disk access, with strong resilience.

  2. ceph-filesystem

    • Access Mode : Filesystem (ReadWriteMany).
    • Use Case : Useful when multiple Pods (distributed across different nodes) need to read and write simultaneously to the same volume (e.g., file sharing, CMS, static assets).

  3. ceph-block-norepl

    • Access Mode : Block (ReadWriteOnce).
    • Replication Factor : X1 (no additional replication).
    • Use Case : Intended for data where replication is already handled at the application level or that does not require high storage-level resilience (caches, ephemeral data).

  4. topolvm-ssd (optional)

    • Access Mode : Local (ReadWriteOnce).
    • Use Case : Node-local storage offering very high performance (low latency). Note that this storage is tied to the physical node. If the node is deleted, the data is deleted as well.

Step 1: Create a PersistentVolumeClaim (PVC)​

A PVC is a storage request. Here is how to create a PVC for each storage type.

Example 1: ceph-block Volume (Default)​

If you do not specify a storageClassName, the ceph-block class will be used by default.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-ceph-block
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  storageClassName: ceph-block

Example 2: Shared Volume ceph-filesystem​

For a volume that can be mounted by multiple Pods simultaneously, use ceph-filesystem with the ReadWriteMany access mode.

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-ceph-fs
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 20Gi
  storageClassName: ceph-filesystem

Example 3: Volume ceph-block-norepl​

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: pvc-ceph-block-norepl
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 10Gi
  storageClassName: ceph-block-norepl

Example 4: Local volume with topolvm​

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

Apply your chosen manifest using the following command:

kubectl apply -f mon-pvc.yaml

You can check the status of your PVC:

kubectl get pvc

The status will change to Bound once the volume is allocated.

Step 2: Using Storage in a Pod​

Once the PVC is created, you can mount it in a Pod by adding it to the volumes and volumeMounts sections.

Here is an example of a Pod using the pvc-ceph-block PVC created previously:

apiVersion: v1
kind: Pod
metadata:
  name: app-storage-demo
spec:
  containers:
  - name: nginx
    image: nginx
    volumeMounts:
    - mountPath: "/usr/share/nginx/html/data"
      name: my-storage
  volumes:
  - name: my-storage
    persistentVolumeClaim:
      claimName: pvc-ceph-block

Apply the manifest:

kubectl apply -f pod.yaml

Verify that the Pod is running:

kubectl get pods

Cleanup​

To free up storage resources, first delete the Pod, then the PVC:

kubectl delete pod app-storage-demo
kubectl delete pvc pvc-ceph-block

Warning : Deleting the PVC will by default delete the underlying volume and the data it contains (according to the ReclaimPolicy of the StorageClass, which is usually Delete).