Static Vs Dynamic Persistent volume (PV) in AKS

 In Azure Kubernetes Service (AKS), a Persistent Volume (PV) is a storage resource in the cluster that can be dynamically provisioned or statically provisioned. The main difference between a PV static and a PV dynamic in AKS is in how they are provisioned.

A PV static is provisioned by an administrator before a pod is created. The administrator creates the PV object and allocates storage capacity from a pre-existing storage resource. The PV object is then used by the pod to access the allocated storage. This approach allows the administrator to manage the storage resources for the cluster and provision the required storage capacity in advance.

On the other hand, a PV dynamic is provisioned on-demand when a pod requests storage. When a pod requests storage, the Kubernetes control plane creates a PV object and allocates storage capacity from a pre-defined storage class. The storage class specifies the type of storage, such as block or file-based storage, and other configuration parameters, such as the storage capacity and the storage location.

The advantage of using a PV dynamic in AKS is that it allows for more flexibility in managing storage resources for the cluster. With dynamic provisioning, you can create and delete PVs on demand, and you can use storage classes to define the type and configuration of storage resources. This approach can help optimize the use of storage resources in the cluster and reduce the management overhead for administrators.

In summary, the main difference between a PV static and a PV dynamic in AKS is that the former is provisioned in advance by an administrator, while the latter is provisioned on-demand when a pod requests storage. Both approaches have their advantages and can be used depending on the requirements of your application and storage management needs.

Example of Static PV Provision:- 

 Create a PV with name pv-azure-file-sql

apiVersion: v1
kind: PersistentVolume
metadata:
  name: pv-azure-file-sql
  labels:
    pv-name: pv-azure-file-sql
spec:
  capacity:
    storage: 10Gi
  accessModes:
    - ReadWriteMany
  storageClassName: azurefile
  azureFile:
    secretName: azure-secret
    shareName: sql-fileshare
    readOnly: false
  mountOptions:
    - dir_mode=0777
    - file_mode=0777
    - uid=10001
    - gid=10001
  persistentVolumeReclaimPolicy: Retain
--- Create a Persistent volume claim 
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc-sql
  namespace: rak
spec:
  accessModes:
    - ReadWriteMany
  resources:
    requests:
      storage: 1Gi
  storageClassName: azurefile
  selector:
    matchLabels:
      pv-name: pv-azure-file-sql
--- Create a deployment which will consume the PVC
apiVersion: apps/v1
kind: Deployment
metadata:
  name: mssql-deployment
  namespace: rak
spec:
  replicas: 1
  selector:
     matchLabels:
       app: mssql
  template:
    metadata:
      labels:
        app: mssql
    spec:
      terminationGracePeriodSeconds: 30
      hostname: mssqlinst
      securityContext:
        fsGroup: 10001
      containers:
      - name: mssql
        image: mcr.microsoft.com/mssql/server:2019-latest
        resources:
          requests:
            memory: "1G"
            cpu: "2000m"
          limits:
            memory: "1G"
            cpu: "2000m"
        ports:
        - containerPort: 1433
        env:
        - name: MSSQL_PID
          value: "Developer"
        - name: ACCEPT_EULA
          value: "Y"
        - name: MSSQL_SA_PASSWORD
          valueFrom:
            secretKeyRef:
              name: mssql
              key: MSSQL_SA_PASSWORD
        volumeMounts:
        - name: mssqldb
          mountPath: /var/opt/mssql
      volumes:
      - name: mssqldb
        persistentVolumeClaim:
          claimName: my-pvc-sql
--- Create a Service which will 
apiVersion: v1
kind: Service
metadata:
  name: mssql-deployment
  namespace: rak
spec:
  selector:
    app: mssql
  ports:
    - protocol: TCP
      port: 1433
      targetPort: 1433
  type: LoadBalancer

---

Example of Dynamic PV Provisioning:-

apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
  name: azure-disk-sc
provisioner: kubernetes.io/azure-disk
parameters:
  storageaccounttype: Standard_LRS
---  
apiVersion: v1
kind: Pod
metadata:
  name: my-pod
  namespace: rak
spec:
  containers:
  - name: my-container
    image: nginx:latest
    volumeMounts:
    - name: my-volume
      mountPath: /data
  volumes:
  - name: my-volume
    persistentVolumeClaim:
      claimName: my-pvc-dynamic
---
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
  name: my-pvc-dynamic
  namespace: rak
spec:
  accessModes:
    - ReadWriteOnce
  resources:
    requests:
      storage: 5Gi
  storageClassName: azure-disk-sc