Storage Peristent

Persistent Storage allows data to survive container or pod terminations, enabling applications like databases to maintain their data over time. This contrasts with the ephemeral storage that is lost when a container or pod is terminated.

Mechanisms:

• Persistent Storage utilizes Persistent Volumes (PVs) and Persistent Volume Claims (PVCs) to abstract storage resources from the underlying storage infrastructure.

Characteristics:

• Persistent Volume (PV): Represents a piece of storage in the cluster.
• Persistent Volume Claim (PVC): A request for storage by a user, acting as a mechanism to consume PVs.
• Storage Classes: In Azure Kubernetes Service (AKS), storage classes define the type of storage provisioned, leveraging Azure Disk, Azure Files, Azure Blob Storage, or Azure NetApp Files.

Azure Storage Classes:

• Azure Disk:
  • default: Standard storage class used by AKS, utilizes Azure Standard SSD.
  • managed premium: Employs Azure Premium SSDs.
• Azure File:
  • azurefile: Uses standard Azure File Storage.
  • azurefile-premium: Uses premium Azure File Storage.
• Blob Storage:
  • blob.csi.azure.com: Integrates Azure Blob Storage using the Blob CSI driver.
• Azure NetApp Files:
  • netapp.io/azurenetapp-csi: Utilizes Azure NetApp Files as a storage class.

Use Cases:

• Data Persistence: Essential for applications that require stable, reliable data storage like databases.
• Stable Working Directory: When used as a working directory, it ensures data persistence across container restarts.

Configuration Examples:

• Pod Configuration with PVC:

Here, a PVC named mypvc is used to mount persistent storage at /app/data in the container.

apiVersion: v1
kind: Pod
metadata:
 name: myapp-pod
spec:
 containers:
 - name: myapp-container
   image: myapp:1.0
   volumeMounts:
   - name: mypersistentvolume
     mountPath: /app/data
 volumes:
 - name: mypersistentvolume
   persistentVolumeClaim:
     claimName: mypvc

• Persistent Volume Claim (PVC) Configuration:

This PVC requests 10GiB of storage from the managed-premium storage class (Azure Premium SSD).

apiVersion: v1
kind: PersistentVolumeClaim
metadata:
 name: mypvc
spec:
 accessModes:
   - ReadWriteOnce
 storageClassName: managed-premium # Azure Premium SSD
 resources:
   requests:
     storage: 10Gi # 10GiB of storage

• Pod with Working Directory and Mounted Volume:

Specifies /app as the working directory of the container and mounts persistent storage at /app/data.

apiVersion: v1
kind: Pod
metadata:
 name: myapp-pod
spec:
 containers:
 - name: myapp-container
   image: myapp:1.0
   workingDir: /app
   volumeMounts:
   - name: mypersistentvolume
     mountPath: /app/data
 volumes:
 - name: mypersistentvolume
   persistentVolumeClaim:
     claimName: mypvc