Dynamically Mounting an EVS Disk to a StatefulSet¶
Application Scenarios¶
Dynamic mounting is available only for creating a StatefulSet. It is implemented through a volume claim template (volumeClaimTemplates field) and depends on the storage class to dynamically provision PVs. In this mode, each pod in a multi-pod StatefulSet is associated with a unique PVC and PV. After a pod is rescheduled, the original data can still be mounted to it based on the PVC name. In the common mounting mode for a Deployment, if ReadWriteMany is supported, multiple pods of the Deployment will be mounted to the same underlying storage.
Prerequisites¶
You have created a cluster and installed the CCE Container Storage (Everest) add-on in the cluster.
If you want to create a cluster using commands, use kubectl to connect to the cluster. For details, see Connecting to a Cluster Using kubectl.
(Console) Dynamically Mounting an EVS Disk¶
Log in to the CCE console and click the cluster name to access the cluster console.
In the navigation pane on the left, click Workloads. In the right pane, click the StatefulSets 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 VolumeClaimTemplate (VTC).
Click Create PVC. In the dialog box displayed, configure the PVC parameters.
Click Create.
Parameter
Description
PVC Type
In this example, select EVS.
PVC Name
Enter the name of the PVC. After a PVC is created, a suffix is automatically added based on the number of pods. The format is <Custom PVC name>-<Serial number>, for example, example-0.
Creation Method
You can select Dynamically provision to create a PVC, PV, and underlying storage on the console in cascading mode.
Storage Classes
The storage class for EVS disks is csi-disk.
AZ
Select the AZ of the EVS disk. The AZ must be the same as that of the cluster node.
Note
An EVS disk can only be mounted to a node in the same AZ. After an EVS disk is created, its AZ cannot be changed.
Disk Type
Select an EVS disk type.
Access Mode
EVS disks support only ReadWriteOnce, indicating that a storage volume can be mounted to one node in read/write mode. For details, see Volume Access Modes.
Capacity (GiB)
Capacity of the requested storage volume.
Encryption
You can select Encryption and an encryption key to encrypt underlying storage. Only EVS disks and SFS file systems support encryption.
Resource Tag
You can add resource tags to classify resources, which is supported only when the Everest version in the cluster is 2.1.39 or later.
You can create predefined tags on the TMS console. The predefined tags are available to all resources that support tags. You can use predefined tags to improve the tag creation and resource migration efficiency.
CCE automatically creates system tags CCE-Cluster-ID={Cluster ID}, CCE-Cluster-Name={Cluster name}, and CCE-Namespace={Namespace name}. These tags cannot be modified.
Note
After a dynamic PV of the EVS type is created, the resource tags cannot be updated on the CCE console. To update these resource tags, go to the EVS console.
Enter the path to which the volume is mounted.
Table 1 Mounting a storage volume¶ Parameter
Description
Mount Path
Enter a mount path, for example, /tmp.
This parameter indicates the 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, causing container startup failures or workload creation failures.
Important
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 machine 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 EVS disk.
Dynamically mount and use storage volumes. For details about other parameters, see Creating a StatefulSet. 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.
Dynamically Mounting an EVS Volume Using kubectl¶
Use kubectl to connect to the cluster.
Create a file named statefulset-evs.yaml. In this example, the EVS volume is mounted to the /data path.
apiVersion: apps/v1 kind: StatefulSet metadata: name: statefulset-evs namespace: default spec: selector: matchLabels: app: statefulset-evs template: metadata: labels: app: statefulset-evs spec: containers: - name: container-1 image: nginx:latest volumeMounts: - name: pvc-disk # The value must be the same as that in the volumeClaimTemplates field. mountPath: /data # Location where the storage volume is mounted. imagePullSecrets: - name: default-secret serviceName: statefulset-evs # Headless Service name. replicas: 2 volumeClaimTemplates: - apiVersion: v1 kind: PersistentVolumeClaim metadata: name: pvc-disk namespace: default annotations: everest.io/disk-volume-type: SAS # EVS disk type. everest.io/crypt-key-id: <your_key_id> # (Optional) Encryption key ID. Mandatory for an encrypted disk. everest.io/disk-volume-tags: '{"key1":"value1","key2":"value2"}' # (Optional) Custom resource tags csi.storage.k8s.io/fstype: xfs # (Optional) Set the file system type to xfs. If it is left blank, ext4 is used by default. labels: failure-domain.beta.kubernetes.io/region: <your_region> # Region of the node where the application is to be deployed. failure-domain.beta.kubernetes.io/zone: <your_zone> # AZ of the node where the application is to be deployed. spec: accessModes: - ReadWriteOnce # The value must be ReadWriteOnce for EVS disks. resources: requests: storage: 10Gi # EVS disk capacity, ranging from 1 to 32768. storageClassName: csi-disk # Storage class type for EVS disks. --- apiVersion: v1 kind: Service metadata: name: statefulset-evs # Headless Service name. namespace: default labels: app: statefulset-evs spec: selector: app: statefulset-evs clusterIP: None ports: - name: statefulset-evs targetPort: 80 nodePort: 0 port: 80 protocol: TCP type: ClusterIP
Table 2 Key parameters¶ Parameter
Mandatory
Description
failure-domain.beta.kubernetes.io/region
Yes
Region where the cluster is located.
For details about the value of region, see Regions and Endpoints.
failure-domain.beta.kubernetes.io/zone
Yes
AZ where the EVS volume is created. It must be the same as the AZ planned for the workload.
For details about the value of zone, see Regions and Endpoints.
everest.io/disk-volume-type
Yes
EVS disk type. All letters are in uppercase.
SATA: common I/O
SAS: high I/O
SSD: ultra-high I/O
everest.io/crypt-key-id
No
Mandatory when the EVS disk is encrypted. Enter the encryption key ID selected during EVS disk creation.
To obtain the encryption key ID, log in to the Cloud Server Console. In the navigation pane, choose Elastic Volume Service > Disks. Click the name of the target EVS disk to go to its details page. On the Summary tab page, copy the value of KMS Key ID in the Configuration Information area.
everest.io/disk-volume-tags
No
This field is optional. It is supported when the Everest version in the cluster is 2.1.39 or later.
You can add resource tags to classify resources.
You can create predefined tags on the TMS console. The predefined tags are available to all resources that support tags. You can use predefined tags to improve the tag creation and resource migration efficiency.
CCE automatically creates system tags CCE-Cluster-ID={Cluster ID}, CCE-Cluster-Name={Cluster name}, and CCE-Namespace={Namespace name}. These tags cannot be modified.
csi.storage.k8s.io/fstype
No
This field is optional. It is supported by nodes running CentOS 7 or Ubuntu 22.04, and when Everest version in the cluster is 2.1.53 or later.
You can use it to configure file system type. The value can be ext4 or xfs. If it is left blank, the default value ext4 is used.
storage
Yes
Requested PVC capacity, in Gi. The value ranges from 1 to 32768.
storageClassName
Yes
The storage class name for EVS disks is csi-disk.
Run the following command to create a workload to which the EVS volume is mounted:
kubectl apply -f statefulset-evs.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.
Verifying Data Persistence¶
View the deployed application and EVS volume files.
Run the following command to view the created pod:
kubectl get pod | grep statefulset-evs
Expected output:
statefulset-evs-0 1/1 Running 0 45s statefulset-evs-1 1/1 Running 0 28s
Run the following command to check whether the EVS volume has been mounted to the /data path:
kubectl exec statefulset-evs-0 -- df | grep data
Expected output:
/dev/sdd 10255636 36888 10202364 0% /data
Run the following command to view the files in the /data path:
kubectl exec statefulset-evs-0 -- ls /data
Expected output:
lost+found
Run the following command to create a file named static in the /data path:
kubectl exec statefulset-evs-0 -- touch /data/static
Run the following command to view the files in the /data path:
kubectl exec statefulset-evs-0 -- ls /data
Expected output:
lost+found static
Run the following command to delete the pod named web-evs-auto-0:
kubectl delete pod statefulset-evs-0
Expected output:
pod "statefulset-evs-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 statefulset-evs-0 -- ls /data
Expected output:
lost+found static
If the static file still exists, the data in the EVS volume can be stored persistently.