Using a Local PV Through a Dynamic PV
Prerequisites
- You have created a cluster and installed the CSI add-on (Everest) in the cluster.
- To create a cluster using commands, ensure kubectl is used. For details, see Connecting to a Cluster Using kubectl.
- You have imported a data disk of a node to the local PV storage pool. For details, see Importing a PV to a Storage Pool.
Notes and Constraints
- Local PVs are supported only when the cluster version is v1.21.2-r0 or later and the Everest add-on version is 2.1.23 or later. Version 2.1.23 or later is recommended.
- Deleting, removing, resetting, or scaling a node will cause the loss of the PVC/PV data of the local PV associated with the node. The lost data cannot be restored, and the affected PVC/PV cannot be used again. In these scenarios, the pod that uses the local PV is evicted from the node. A new pod will be created and stay in the pending state. This is because the PVC used by the pod has a node label, due to which the pod cannot be scheduled. After the node is reset, the pod may be scheduled to the reset node. In this case, the pod remains in the creating state because the underlying logical volume corresponding to the PVC does not exist.
- Do not manually delete the corresponding storage pool or detach data disks from the node. Otherwise, exceptions such as data loss may occur.
- Local PVs are in non-shared mode and cannot be mounted to multiple workloads or tasks concurrently. Additionally, local PVs cannot be mounted to multiple pods of a workload concurrently.
Automatically Creating a Local PV on the Console
- Log in to the CCE console and click the cluster name to access the cluster console.
- Dynamically create a PVC and PV.
- Choose Storage in the navigation pane. In the right pane, click the PVCs tab. Click Create PVC in the upper right corner. In the dialog box displayed, configure PVC parameters.
Parameter
Description
PVC Type
In this section, select Local PV.
PVC Name
Enter the PVC name, which must be unique in a namespace.
Creation Method
You can only select Dynamically provision to create a PVC, PV, and underlying storage on the console in cascading mode.
Storage Classes
The storage class of local PVs is csi-local-topology.
(Optional) Storage Volume Name Prefix
Available only when the cluster version is v1.23.14-r0, v1.25.9-r0, v1.27.6-r0, v1.28.4-r0, or later, and Everest of v2.4.15 or later is installed in the cluster.
This parameter specifies the name of the underlying storage that is automatically created. The actual underlying storage name is in the format of "Storage volume name prefix + PVC UID". If this parameter is left blank, the default prefix pvc will be used.
For example, if the storage volume name prefix is set to test, the actual underlying storage name is test-{UID}.
Capacity (GiB)
Capacity of the requested storage volume.
Access Mode
Local PVs support only ReadWriteOnce, indicating that a PV can be mounted to one node in read/write mode. For details, see Volume Access Modes.
Storage Pool
View the imported storage pool. For details about how to import a new data volume to the storage pool, see Importing a PV to a Storage Pool.
- Click Create to create a PVC and a PV.
You can choose Storage in the navigation pane and view the created PVC and PV on the PVCs and PVs tab pages, respectively.
The volume binding mode of the local storage class (named csi-local-topology) is late binding (that is, the value of volumeBindingMode is WaitForFirstConsumer). In this mode, PV creation and binding are delayed. The corresponding PV is created and bound only when the PVC is used during workload creation.
- Choose Storage in the navigation pane. In the right pane, click the PVCs tab. Click Create PVC in the upper right corner. In the dialog box displayed, configure PVC parameters.
- Create an application.
- Choose Workloads in the navigation pane. In the right pane, click the Deployments tab.
- Click Create Workload in the upper right corner. On the displayed page, click Data Storage in the Container Settings area and click Add Volume to select PVC.
Mount and use storage volumes, as shown in Table 1. For details about other parameters, see Workloads.
Table 1 Mounting a storage volume Parameter
Description
PVC
Select an existing local PV.
A local PV can be mounted to only one workload.
Mount Path
Enter a mount path, for example, /tmp.
This parameter specifies a container path to which a data volume will be mounted. Do not mount the volume to a system directory such as / or /var/run. Otherwise, containers will be malfunctional. Mount the volume to an empty directory. If the directory is not empty, ensure that there are no files that affect container startup. Otherwise, the files will be replaced, leading to container startup failures or workload creation failures.NOTICE:If a volume is mounted to a high-risk directory, use an account with minimum permissions to start the container. Otherwise, high-risk files on the host may be damaged.
Subpath
Enter the subpath of the storage volume and mount a path in the storage volume to the container. In this way, different folders of the same storage volume can be used in a single pod. tmp, for example, indicates that data in the mount path of the container is stored in the tmp folder of the storage volume. If this parameter is left blank, the root path is used by default.
Permission
- Read-only: You can only read the data in the mounted volumes.
- Read-write: You can modify the data volumes mounted to the path. Newly written data will not be migrated if the container is migrated, which may cause data loss.
In this example, the disk is mounted to the /data path of the container. The container data generated in this path is stored in the local PV.
- After the configuration, click Create Workload.
After the workload is created, the data in the container mount directory will be persistently stored. Verify the storage by referring to Verifying Data Persistence.
Automatically Creating a Local PV Through kubectl
- Use kubectl to access the cluster.
- Use StorageClass to dynamically create a PVC and PV.
- Create the pvc-local.yaml file.
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: pvc-local namespace: default annotations: everest.io/csi.volume-name-prefix: test # (Optional) Storage volume name prefix of the automatically created underlying storage spec: accessModes: - ReadWriteOnce # The value must be ReadWriteOnce for local PVs. resources: requests: storage: 10Gi # Local PV capacity storageClassName: csi-local-topology # StorageClass is local PV.
Table 2 Key parameters Parameter
Mandatory
Description
everest.io/csi.volume-name-prefix
No
(Optional) This parameter is available only when the cluster version is v1.23.14-r0, v1.25.9-r0, v1.27.6-r0, v1.28.4-r0, or later, and Everest of v2.4.15 or later is installed in the cluster.
This parameter specifies the name of the underlying storage that is automatically created. The actual underlying storage name is in the format of "Storage volume name prefix + PVC UID". If this parameter is left blank, the default prefix pvc will be used.
Enter 1 to 26 characters that cannot start or end with a hyphen (-). Only lowercase letters, digits, and hyphens (-) are allowed.
For example, if the storage volume name prefix is set to test, the actual underlying storage name is test-{UID}.
storage
Yes
Requested capacity in the PVC, in Gi.
storageClassName
Yes
StorageClass name, which is csi-local-topology for a local PV.
- Run the following command to create a PVC:
kubectl apply -f pvc-local.yaml
- Create the pvc-local.yaml file.
- Create an application.
- Create a file named web-local.yaml. In this example, the local PV is mounted to the /data path.
apiVersion: apps/v1 kind: StatefulSet metadata: name: web-local namespace: default spec: replicas: 1 selector: matchLabels: app: web-local serviceName: web-local # Headless Service name template: metadata: labels: app: web-local spec: containers: - name: container-1 image: nginx:latest volumeMounts: - name: pvc-disk # Volume name, which must be the same as the volume name in the volumes field. mountPath: /data # Location where the storage volume is mounted imagePullSecrets: - name: default-secret volumes: - name: pvc-disk # Volume name, which can be customized persistentVolumeClaim: claimName: pvc-local # Name of the created PVC --- apiVersion: v1 kind: Service metadata: name: web-local # Headless Service name namespace: default labels: app: web-local spec: selector: app: web-local clusterIP: None ports: - name: web-local targetPort: 80 nodePort: 0 port: 80 protocol: TCP type: ClusterIP
- Run the following command to create a workload to which the local PV is mounted:
kubectl apply -f web-local.yaml
After the workload is created, the data in the container mount directory will be persistently stored. Verify the storage by referring to Verifying Data Persistence.
- Create a file named web-local.yaml. In this example, the local PV is mounted to the /data path.
Verifying Data Persistence
- View the deployed application and local files.
- Run the following command to view the created pod:
kubectl get pod | grep web-local
Expected output:web-local-0 1/1 Running 0 38s
- Run the following command to check whether the local PV has been mounted to the /data path:
kubectl exec web-local-0 -- df | grep data
Expected output:
/dev/mapper/vg--everest--localvolume--persistent-pvc-local 10255636 36888 10202364 0% /data
- Run the following command to check the files in the /data path:
kubectl exec web-local-0 -- ls /data
Expected output:
lost+found
- Run the following command to view the created pod:
- Run the following command to create a file named static in the /data path:
kubectl exec web-local-0 -- touch /data/static
- Run the following command to check the files in the /data path:
kubectl exec web-local-0 -- ls /data
Expected output:
lost+found static
- Run the following command to delete the pod named web-local-0:
kubectl delete pod web-local-0
Expected output:
pod "web-local-0" deleted
- After the deletion, the StatefulSet controller automatically creates a replica with the same name. Run the following command to check whether the files in the /data path have been modified:
kubectl exec web-local-0 -- ls /data
Expected output:
lost+found static
The static file is retained, indicating that the data in the local PV can be stored persistently.
Related Operations
Operation |
Description |
Procedure |
---|---|---|
Viewing events |
View event names, event types, number of occurrences, Kubernetes events, first occurrence time, and last occurrence time of the PVC or PV. |
|
Viewing a YAML file |
View, copy, or download the YAML file of a PVC or PV. |
|
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