Understanding Kubernetes Storage: Volumes, PVs, PVCs, and AWS Storage Options

Kubernetes storage is a crucial aspect of running stateful applications in a cluster. In this blog, we will cover key storage concepts such as Volumes, Storage Classes, Persistent Volumes (PVs), Persistent Volume Claims (PVCs), provisioning types, retention policies, and AWS storage options like EBS and EFS.

1. Kubernetes Storage Fundamentals Volumes in Kubernetes Kubernetes Volumes provide storage to containers running in a Pod. Unlike ephemeral container storage, Kubernetes Volumes persist as long as the Pod is running. Types of Volumes: emptyDir - Temporary storage that gets erased when the Pod is deleted. hostPath - Mounts a directory from the node’s filesystem. configMap/Secret - Used for storing configuration data securely. Persistent Volumes (PVs) - More advanced storage that can be dynamically or statically provisioned.

2. Persistent Storage in Kubernetes Persistent Volumes (PVs) and Persistent Volume Claims (PVCs) Persistent Volumes (PVs): Cluster-wide resources provisioned by administrators or dynamically by Storage Classes. Persistent Volume Claims (PVCs): Requests for storage by applications, which are bound to PVs.

Example PVC YAML: apiVersion: v1 kind: PersistentVolumeClaim metadata: name: my-pvc spec: accessModes: - ReadWriteOnce resources: requests: storage: 10Gi storageClassName: ebs-sc 3. Storage Classes and Provisioning Storage Classes A StorageClass defines how storage is provisioned dynamically. It allows users to specify different storage types and policies. Example StorageClass YAML: apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: ebs-sc annotations: storageclass.kubernetes.io/is-default-class: “true” provisioner: ebs.csi.aws.com allowVolumeExpansion: true volumeBindingMode: WaitForFirstConsumer reclaimPolicy: Delete parameters: type: gp3 fsType: ext4 encrypted: “true” Static vs. Dynamic Provisioning Static Provisioning: Admins create PVs manually and bind them to PVCs. Dynamic Provisioning: Kubernetes automatically provisions storage when a PVC is created.

4. Retention Policies in Kubernetes Storage Delete: The PV is deleted when the PVC is deleted. Retain: The PV remains even if the PVC is deleted, requiring manual cleanup. Recycle (deprecated): The volume is scrubbed and made available again.

5. AWS Storage Options for Kubernetes Amazon EBS (Elastic Block Store) Best for block storage that needs high performance.

Used with stateful applications like databases.

Requires PV, PVC, and StorageClass configurations.

Amazon EFS (Elastic File System) A fully managed NFS-based file system.

Supports multiple Pods accessing the same volume.

Ideal for shared storage use cases.

Example EFS StorageClass YAML: apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: efs-sc provisioner: efs.csi.aws.com parameters: fileSystemId: fs-12345678 provisioningMode: efs-ap directoryPerms: “777” Conclusion Kubernetes provides powerful storage options for running stateful applications. Understanding volumes, PVs, PVCs, Storage Classes, and AWS storage solutions like EBS and EFS ensures that your applications have the persistent storage they need.