Implement storage classes and dynamic volume provisioning
5 minutes
5 Questions
In the context of the CKA exam, implementing storage classes and dynamic volume provisioning shifts storage management from a manual, static process to an automated, on-demand workflow.
Traditionally, administrators practiced **Static Provisioning**, where they manually created `PersistentVolume` …In the context of the CKA exam, implementing storage classes and dynamic volume provisioning shifts storage management from a manual, static process to an automated, on-demand workflow.
Traditionally, administrators practiced **Static Provisioning**, where they manually created `PersistentVolume` (PV) objects representing physical disks before a developer could claim them. This created an administrative bottleneck. **Dynamic Volume Provisioning** solves this by allowing storage volumes to be created on-demand using a **`StorageClass`**.
A `StorageClass` acts as a template or profile for storage (e.g., 'gold' for fast SSDs, 'silver' for HDDs). To implement this, you define a YAML manifest with:
1. **Provisioner**: The plugin that handles volume creation (e.g., a Cloud Provider or CSI driver).
2. **Parameters**: Backend-specific details (e.g., disk type `gp2`, IOPS).
3. **ReclaimPolicy**: Usually set to `Delete` or `Retain`, dictating what happens to the volume when the claim is deleted.
The workflow occurs as follows: The administrator creates the `StorageClass`. A user then creates a `PersistentVolumeClaim` (PVC) that references the class via the `storageClassName` field. The Kubernetes control plane detects this claim, communicates with the storage provider to provision the disk, automatically creates the PV object, and binds it to the PVC.
For the exam, remember that if `storageClassName` is omitted in a PVC, the cluster's **Default StorageClass** (marked via the annotation `storageclass.kubernetes.io/is-default-class: "true"`) is used. If set to an empty string (`""`), dynamic provisioning is disabled. Mastering this ensures scalable, self-service storage for stateful workloads.
Storage Classes and Dynamic Provisioning Guide
Why is it Important? In a static provisioning model, cluster administrators must manually create Persistent Volumes (PVs) before developers can create claims (PVCs) to use them. This is inefficient and unscalable. Dynamic Volume Provisioning automates this process. It allows storage volumes to be created on-demand when a user requests them via a PVC, eliminating the need for administrators to pre-provision storage.
What is it? The core abstraction is the StorageClass. It serves as a template for creating volumes. It tells Kubernetes which provisioner to use (e.g., AWS EBS, Google Persistent Disk, Azure File) and what parameters to apply (e.g., IOPS, replication type). When a PVC specifies a storageClassName, Kubernetes uses that class to dynamically provision a PV.
How it Works: 1. Admin creates a StorageClass resource defining a provisioner. 2. User creates a PersistentVolumeClaim (PVC) referencing that StorageClass. 3. Kubernetes calls the defined Provisioner plugin. 4. The provisioner creates the actual storage on the backend infrastructure. 5. Kubernetes automatically generates a PersistentVolume (PV) object representing that storage and binds it to the PVC.
How to Answer Exam Questions: Step 1: Define the StorageClass. Create a YAML file defining the class. Ensure the provisioner matches the question requirements (e.g., kubernetes.io/no-provisioner for local tests or a specific cloud provider). Step 2: Define the PVC. Create the claim YAML. The most critical field is storageClassName, which must match the name of the StorageClass you created. Step 3: Verify. Apply both manifests. Run kubectl get pvc and ensure the status turns to Bound. Note that a PV was created automatically.
Exam Tips: Answering Questions on Implement storage classes and dynamic volume provisioning 1. VolumeBindingMode: Pay close attention to this field in the StorageClass. If set to WaitForFirstConsumer, the PVC will remain in a Pending state until a Pod actually tries to use it. Do not panic if the PVC doesn't bind immediately; check if a Pod is required. 2. ReclaimPolicy: Questions often specify what should happen to the data if the PVC is deleted. Set reclaimPolicy to Retain (keep data) or Delete (destroy data) as requested. 3. Default Class: If a PVC does not specify a storageClassName, it uses the cluster's default class. You can toggle the default class behavior by annotating a StorageClass with storageclass.kubernetes.io/is-default-class="true". 4. Troubleshooting: If your dynamic provisioning fails, use kubectl describe pvc <pvc-name>. The Events section will tell you exactly why the provisioner failed (e.g., quota issues, wrong parameters, or missing provisioner).