Docker Storage and Kubernetes Integration 📦

Docker Storage Overview 🐳

Volume Creation

• Auto-creation: Docker automatically creates a volume if not explicitly defined.
• Newer Way to Mount Volumes: Utilize modern methods for mounting volumes in Docker containers.

Types of Docker Storage

• Local Storage: Mounting a local folder inside the container as a volume.
• Third-Party Storage: Integration with external storage solutions such as AWS EBS volumes.

Kubernetes Storage 🗂️

Kubernetes Runtime Interfaces

• Container Runtime Interface (CRI): Integrates container runtimes.
• Container Network Interface (CNI): Integrates network plugins.
• Container Storage Interface (CSI): Integrates storage plugins.

Host Folder Mounting

• Mounting a Host Folder: Example of mounting a host path inside the container as a volume.

  volumeMounts:
    - mountPath: /data
      name: data-volume
  volumes:
    - name: data-volume
      hostPath:
        path: /data
  • Note: This method is not recommended for multi-node clusters. Instead, use third-party solutions like AWS EBS, Azure Disk, or Google Cloud Persistent Disk to manage data centrally.

Persistent Volumes (PV) and Persistent Volume Claims (PVC)

Creating a Persistent Volume (PV)

• Mount AWS EBS Volume in all nodes for equal data persistence.

  apiVersion: v1
  kind: PersistentVolume
  metadata:
    name: example-pv
  spec:
    capacity:
      storage: 5Gi
    accessModes:
      - ReadWriteOnce
    persistentVolumeReclaimPolicy: Retain
    storageClassName: standard
    awsElasticBlockStore:
      volumeID: <volume-id>
      fsType: ext4

Access Modes for PV

• HostPath: Example /tmp/data is not recommended for production. Prefer third-party storage solutions.

Creating a Persistent Volume Claim (PVC)

• Example PVC for claiming the PV.

  apiVersion: v1
  kind: PersistentVolumeClaim
  metadata:
    name: example-pvc
  spec:
    accessModes:
      - ReadWriteOnce
    resources:
      requests:
        storage: 500Mi
    storageClassName: standard

Reclaim Policies

• Delete: Deletes the PV when PVC is deleted.
• Recycle: Makes PV available and flushes data when PVC is deleted.
• Retain: Retains data and PV is not available for new claims when PVC is deleted.

Attaching PV & PVC to a Pod

• Specify the PVC claim name under persistentVolumeClaim section in the volumes section of the pod definition file.

  apiVersion: v1
  kind: Pod
  metadata:
    name: example-pod
  spec:
    containers:
      - name: example-container
        image: nginx
        volumeMounts:
          - mountPath: /data
            name: data-volume
    volumes:
      - name: data-volume
        persistentVolumeClaim:
          claimName: example-pvc

Storage Class (Dynamic Storage) 📦

• Use StorageClass for dynamic provisioning of storage.

  apiVersion: storage.k8s.io/v1
  kind: StorageClass
  metadata:
    name: standard
  provisioner: kubernetes.io/aws-ebs
  parameters:
    type: gp2

• Check available storage classes:

  kubectl get storageclass