Dynamically Mounting an EVS Disk to a StatefulSet_Cloud Container Engine

Application Scenarios

Dynamic mounting is available only for creating a StatefulSet. It is implemented through a volume claim template (volumeClaimTemplates field) and depends on dynamic creation of PVs through StorageClass. 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.

When updating a StatefulSet in Kubernetes, it is not allowed to add or delete the volumeClaimTemplates field. This field can only be configured during the creation of the StatefulSet.

Prerequisites

You have created a cluster and installed the CCE Container Storage (Everest) add-on in the cluster.
To create a cluster using commands, ensure kubectl is used. For details, see Connecting to a Cluster Using kubectl.

Dynamically Mounting an EVS Disk on the Console

Log in to the CCE console and click the cluster name to access the cluster console.
Choose Workloads in the navigation pane. 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.

Click Create PVC. In the dialog box displayed, configure 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 default StorageClass for EVS disks is csi-disk. You can customize a StorageClass and configure its reclaim policy and binding mode. For details, see Creating a StorageClass Using the CCE Console.
(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}.
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. EVS disk types vary depending on regions. Obtain the available EVS types on the console. NOTE: If the Everest version is 2.4.4 or later, general-purpose SSD V2 EVS disks are supported. General-purpose SSD V2 disks allow you to specify the disk IOPS and throughput. For details, see EVS performance data.
Capacity (GiB)	Capacity of the requested storage volume.
Billing Mode	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 v2.4.16 or later is installed in the cluster. Options: Yearly/Monthly Resources will be billed on a yearly/monthly basis. To use the yearly/monthly billing mode, you need to select the required duration, and auto-renewal is enabled by default. Your order will automatically renew on a monthly or yearly basis, depending on if you purchased by month or by year. Pay-per-use Resources will be billed based on usage duration. You can provision or delete resources at any time.
Access Mode	EVS volumes support only ReadWriteOnce, indicating that a storage volume can be mounted to one node in read/write mode. For details, see Volume Access Modes.
Encryption	Configure whether to encrypt underlying storage. If you select Enabled (key), an encryption key must be configured. Before using encryption, check whether the region where the EVS disk is located supports disk encryption.
Enterprise Project	The default enterprise project, the enterprise project to which the cluster belongs, or the enterprise project specified by StorageClass is available.
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. For details, see Creating Predefined Tags. 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 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. This may lead to container errors. 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 will be 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.

Click to enlarge

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 Through kubectl

Use kubectl to access 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/enterprise-project-id: <your_project_id>  # (Optional) Enterprise project ID. If an enterprise project is specified, use the same enterprise project when creating a PVC. Otherwise, the PVC cannot be bound to a PV.
          everest.io/disk-iops: '3000'      # (Optional) IOPS of only a GPSSD2 EVS disk
          everest.io/disk-throughput: '125' # (Optional) Throughput of only a GPSSD2 EVS disk
          everest.io/csi.charging-mode: prePaid  # (Optional) Yearly/Monthly billing mode
          everest.io/csi.period-type: month      # Mandatory if the billing mode is set to Yearly/Monthly. month indicates that resources will be billed on a monthly basis.
          everest.io/csi.period-num: '1'         # Mandatory if the billing mode is set to Yearly/Monthly. '1' indicates that the required duration is one month.
          everest.io/csi.volume-name-prefix: test  # (Optional) Storage volume name prefix of the automatically created underlying storage
        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    # StorageClass is EVS
---
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 its value, 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 its value, see Regions and Endpoints.
everest.io/disk-volume-type	Yes	EVS disk type. All letters are in uppercase. SAS: high I/O SSD: ultra-high I/O GPSSD: general-purpose SSD ESSD: extreme SSD GPSSD2: general-purpose SSD v2, which is supported when the Everest version is 2.4.4 or later and the everest.io/disk-iops and everest.io/disk-throughput annotations are configured
everest.io/disk-iops	No	Preconfigured IOPS, which is supported only by general-purpose SSD v2 EVS disks. The IOPS of general-purpose SSD v2 EVS disks ranges from 3000 to 128000, and the maximum value is 500 times of the capacity (GiB). If the IOPS of general-purpose SSD v2 disks is greater than 3000, extra IOPS will be billed. For details, see Price Calculator.
everest.io/disk-throughput	No	Preconfigured throughput, which is supported only by general-purpose SSD v2 EVS disks. The value ranges from 125 MiB/s to 1000 MiB/s. The maximum value is a quarter of IOPS. If the throughput is greater than 125 MiB/s, extra throughput will be billed. For details, see Price Calculator.
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 an 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/enterprise-project-id	No	Optional. Enterprise project ID of the EVS disk. If an enterprise project is specified, use the same enterprise project when creating a PVC. Otherwise, the PVC cannot be bound to a PV. To obtain an enterprise project 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, click the enterprise project in Management Information to access the enterprise project console. Copy the corresponding ID to obtain the ID of the enterprise project to which the EVS disk belongs.
everest.io/csi.charging-mode	No	Optional, indicating the billing mode. If this parameter is left blank, resources will be billed on a pay-per-use basis. 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 v2.4.16 or later is installed in the cluster. Options: prePaid: EVS disks are billed on a yearly/monthly basis, and auto-renewal is enabled by default. Your order will automatically renew on a monthly or yearly basis, depending on if you purchased by month or by year. postPaid: EVS disks are billed on a pay-per-use basis. NOTE: Before creating an EVS disk billed on a yearly/monthly basis, you need to grant the payment permission (bss:order:pay) to cce_cluster_agency. Use your tenant account on the CCE console to perform this operation for the first time. After confirmation, CCE will automatically authorize the agency.
everest.io/csi.period-type	No	Billing cycle, which is mandatory only when the yearly/monthly billing mode is used. Options: month: Resources are billed on a monthly basis. year: Resources are billed on a yearly basis.
everest.io/csi.period-num	No	Required duration, which is mandatory only when the yearly/monthly billing mode is used. Options: For monthly billing, the value of this parameter ranges from 1 to 9. For yearly billing, the value of this parameter is 1.
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 PVC capacity, in Gi. The value ranges from 1 to 32768.
storageClassName	Yes	The StorageClass 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 check 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 check 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
```
The static file is retained, indicating that the data in the EVS volume can be stored persistently.

Related Operations

You can also perform the operations listed in Table 3.

**Table 3** Related operations
Operation	Description	Procedure
Expanding the capacity of an EVS disk	Quickly expand the capacity of an attached EVS disk on the CCE console. Only the capacity of pay-per-use EVS disks can be expanded on the CCE console. To expand the capacity of yearly/monthly EVS disks, click the volume name to go to the EVS console.	Choose Storage in the navigation pane. In the right pane, click the PVCs tab. Click More in the Operation column of the target PVC and select Scale-out. Enter the capacity to be added and click OK.
Viewing events	View event names, event types, number of occurrences, Kubernetes events, first occurrence time, and last occurrence time of the PVC or PV.	Choose Storage in the navigation pane. In the right pane, click the PVCs or PVs tab. Click View Events in the Operation column of the target PVC or PV to view events generated within one hour (events are retained for one hour).
Viewing a YAML file	View, copy, or download the YAML file of a PVC or PV.	Choose Storage in the navigation pane. In the right pane, click the PVCs or PVs tab. Click View YAML in the Operation column of the target PVC or PV to view or download the YAML.

Dynamically Mounting an EVS Disk to a StatefulSet