With the popularity of containerization technology, Kubernetes has become the platform of choice for cloud-native application deployment and management. However, while enjoying the advantages of elastic scaling and high availability brought by Kubernetes, how to ensure data persistence has become a key issue.PersistentVolume (PV), as a kind of storage resource abstraction in Kubernetes, provides powerful support for solving the data persistence problem. In this article, we will introduce in detail how PersistentVolume works, how to configure it, and sample code to help readers better understand and apply this feature.

PersistentVolume Working Principle
PersistentVolume (PV) is an object used to represent persistent storage resources in Kubernetes. It hides the underlying implementation details of storage, such as Ceph, GlusterFS, NFS, and so on, so that users can focus only on the capacity, access mode, and other attributes of the storage without having to care about the specific storage technology.PVs are created and maintained by cluster administrators, and Pods request and use these storage resources through PersistentVolumeClaim (PVC). The

Configuring PersistentVolume
The following is a sample configuration file (in YAML format) for creating a PersistentVolume:

yaml
apiVersion: v1
kind: PersistentVolume
apiVersion: v1 kind: PersistentVolume
name: my-pv
metadata: name: my-pv
my-pv metadata: name: my-pv spec.
storage: 1Gi
accessModes: readWriteOnce

- ReadWriteOnce  

persistentVolumeReclaimPolicy: Retain
storageClassName: manual
hostPath: path: “/mnt/data
path: “/mnt/data”
In this example, we create a PersistentVolume named my-pv with a capacity of 1GiB and an access mode of ReadWriteOnce (i.e., it can only be mounted in read/write mode by a Pod on a single node). persistentVolumeReclaimPolicy is set to Retain, which says that When the PV is no longer needed, its underlying storage resources will not be automatically deleted, but will need to be handled manually by the administrator. storageClassName is set to manual to indicate that this is a manually-created PV, or it can be set to a dynamic storage class to support the automatic creation of PVs. hostPath specifies the path of the storage volume to the host computer.

Creating PersistentVolumeClaim
Pods request storage resources through PersistentVolumeClaim (PVC). The following is a sample configuration file for a PVC:

yaml
apiVersion: v1
kind: PersistentVolumeClaim
metadata: name: my-pvc
name: my-pvc
metadata: name: my-pvc
accessModes: readWriteOnce

- ReadWriteOnce  

resources.
requests: my-pvc spec: accessModes: ReadWriteOnce resources.
storage: 1Gi
storageClassName: manual
In this example, we create a PersistentVolumeClaim named my-pvc that requests 1GiB of storage, has an access mode of ReadWriteOnce, and specifies a storage class of manual to match the previously created PV.

Using PVCs
Pods use storage resources by specifying the name of a PVC in their configuration file. The following is a sample configuration of a Pod using PVCs:

yaml
apiVersion: v1
kind: Pod
apiVersion: v1 kind: Pod metadata.
name: my-pod
containers: containers: my-pod
containers: name: my-container

• name: my-container
  image: nginx
  volumeMounts: name: my-volume 
  • name: my-volume
    mountPath: “/usr/share/nginx/html”
    volumeMounts: name: my-volume
• name: my-volume
  persistentVolumeClaim: name: my-volume
  claimName: my-pvc
  In this example, the container my-container in Pod my-pod mounts the volume named my-volume to the /usr/share/nginx/html path via the volumeMounts field. And the persistentVolumeClaim in the volumes field specifies that the volume is obtained via PVC my-pvc.

To summarize
With PersistentVolume and PersistentVolumeClaim, Kubernetes provides flexible and powerful support for data persistence. Cluster administrators can create and manage a variety of storage resources, while developers can easily request and use these resources via PVCs without having to care about the specific implementation of the underlying storage. This decoupled design allows Kubernetes to better adapt to different storage needs and environments.