StorageClass¶
Introduction¶
StorageClass describes the classification of storage types in a cluster and can be represented as a configuration template for creating PVs. When creating a PVC or PV, specify StorageClass.
As a user, you only need to specify storageClassName when defining a PVC to automatically create a PV and underlying storage, significantly reducing the workload of creating and maintaining a PV.
In addition to the default storage classes provided by CCE, you can also customize storage classes.
CCE Default Storage Classes¶
As of now, CCE provides storage classes such as csi-disk, csi-nas, and csi-obs by default. When defining a PVC, you can use a storageClassName to automatically create a PV of the corresponding type and automatically create underlying storage resources.
Run the following kubectl command to obtain the storage classes that CCE supports. Use the CSI add-on provided by CCE to create a storage class.
# kubectl get sc
NAME PROVISIONER AGE
csi-disk everest-csi-provisioner 17d # EVS disk
csi-disk-topology everest-csi-provisioner 17d # EVS disks created with delay
csi-nas everest-csi-provisioner 17d # SFS 1.0
csi-obs everest-csi-provisioner 17d # OBS
csi-sfsturbo everest-csi-provisioner 17d # SFS Turbo
Each storage class contains the default parameters used for dynamically creating a PV. The following is an example of storage class for EVS disks:
kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
name: csi-disk
provisioner: everest-csi-provisioner
parameters:
csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io
csi.storage.k8s.io/fstype: ext4 # (Optional) Set the file system type to xfs or ext4. If it is left blank, ext4 will be used by default.
everest.io/disk-volume-type: SAS
everest.io/passthrough: 'true'
reclaimPolicy: Delete
allowVolumeExpansion: true
volumeBindingMode: Immediate
Parameter | Description |
|---|---|
provisioner | Specifies the storage resource provider, which is the Everest add-on for CCE. Set this parameter to everest-csi-provisioner. |
parameters | Specifies the storage parameters, which vary with storage types. For details, see Table 2. |
reclaimPolicy | Specifies the value of persistentVolumeReclaimPolicy for creating a PV. The value can be Delete or Retain. If reclaimPolicy is not specified when a StorageClass object is created, the value defaults to Delete.
|
allowVolumeExpansion | Specifies whether the PV of this storage class supports dynamic capacity expansion. The default value is false. Dynamic capacity expansion is implemented by the underlying storage add-on. This is only a switch. |
volumeBindingMode | Specifies the volume binding mode, that is, the time when a PV is dynamically created. The value can be Immediate or WaitForFirstConsumer.
|
mountOptions | This field must be supported by the underlying storage. If this field is not supported but is specified, the PV creation will fail. |
Volume Type | Parameter | Mandatory | Description |
|---|---|---|---|
EVS | csi.storage.k8s.io/csi-driver-name | Yes | Driver type. If an EVS disk is used, the parameter value is fixed at disk.csi.everest.io. |
csi.storage.k8s.io/fstype | Yes | If an EVS disk is used, the parameter value can be ext4 or xfs. The restrictions on using xfs are as follows:
| |
everest.io/disk-volume-type | Yes | EVS disk type. All letters are in uppercase.
| |
everest.io/passthrough | Yes | The parameter value is fixed at true, which indicates that the EVS device type is SCSI. Other parameter values are not allowed. | |
SFS | csi.storage.k8s.io/csi-driver-name | Yes | Driver type. If SFS is used, the parameter value is fixed at nas.csi.everest.io. |
csi.storage.k8s.io/fstype | Yes | If SFS is used, the value can be nfs. | |
everest.io/share-access-level | Yes | The parameter value is fixed at rw, indicating that the SFS data is readable and writable. | |
everest.io/share-access-to | Yes | VPC ID of the cluster. | |
everest.io/share-is-public | No | The parameter value is fixed at false, indicating that the file is shared to private. You do not need to configure this parameter when SFS 3.0 is used. | |
everest.io/sfs-version | No | This parameter is mandatory only when SFS 3.0 is used. The value is fixed at sfs3.0. | |
SFS Turbo | csi.storage.k8s.io/csi-driver-name | Yes | Driver type. If SFS Turbo is used, the parameter value is fixed at sfsturbo.csi.everest.io. |
csi.storage.k8s.io/fstype | Yes | If SFS Turbo is used, the value can be nfs. | |
everest.io/share-access-to | Yes | VPC ID of the cluster. | |
everest.io/share-expand-type | No | Extension type. The default value is bandwidth, indicating an enhanced file system. This parameter does not take effect. | |
everest.io/share-source | Yes | The parameter value is fixed at sfs-turbo. | |
everest.io/share-volume-type | No | SFS Turbo storage class. The default value is STANDARD, indicating standard and standard enhanced editions. This parameter does not take effect. | |
OBS | csi.storage.k8s.io/csi-driver-name | Yes | Driver type. If OBS is used, the parameter value is fixed at obs.csi.everest.io. |
csi.storage.k8s.io/fstype | Yes | Instance type, which can be obsfs or s3fs.
| |
everest.io/obs-volume-type | Yes | OBS storage class.
|
Application Scenarios of Custom Storage¶
When using storage resources in CCE, the most common method is to specify storageClassName to define the type of storage resources to be created when creating a PVC. The following configuration shows how to use a PVC to apply for a SAS (high I/O) EVS disk (block storage).
apiVersion: v1
kind: PersistentVolumeClaim
metadata:
name: pvc-evs-example
namespace: default
annotations:
everest.io/disk-volume-type: SAS
spec:
accessModes:
- ReadWriteOnce
resources:
requests:
storage: 10Gi
storageClassName: csi-disk
To specify the EVS disk type on CCE, use the everest.io/disk-volume-type field. SAS indicates the EVS disk type.
The preceding is a basic method of using StorageClass. In real-world scenarios, you can use StorageClass to perform other operations.
Application Scenario | Solution | Procedure |
|---|---|---|
When annotations is used to specify storage configuration, the configuration is complex. For example, the everest.io/disk-volume-type field is used to specify the EVS disk type. | Define PVC annotations in the parameters field of StorageClass. When compiling a YAML file, you only need to specify storageClassName. For example, you can define SAS EVS disk and SSD EVS disk as a storage class, respectively. If a storage class named csi-disk-sas is defined, it is used to create SAS storage. | |
When a user migrates services from a self-built Kubernetes cluster or other Kubernetes services to CCE, the storage class used in the original application YAML file is different from that used in CCE. As a result, a large number of YAML files or Helm chart packages need to be modified when the storage is used, which is complex and error-prone. | Create a storage class with the same name as that in the original application YAML file in the CCE cluster. After the migration, you do not need to modify the storageClassName in the application YAML file. For example, the EVS disk storage class used before the migration is disk-standard. After migrating services to a CCE cluster, you can copy the YAML file of the csi-disk storage class in the CCE cluster, change its name to disk-standard, and create another storage class. | |
storageClassName must be specified in the YAML file to use the storage. If not, the storage cannot be created. | If you set the default StorageClass in the cluster, you can create storage without specifying the storageClassName in the YAML file. |
Custom Storage Class¶
This section uses the custom storage class of EVS disks as an example to describe how to define SAS EVS disk and SSD EVS disk as a storage class, respectively. For example, if you define a storage class named csi-disk-sas, which is used to create SAS storage, the differences are shown in the following figure. When compiling a YAML file, you only need to specify storageClassName.
You can customize a high I/O storage class in a YAML file. For example, the name csi-disk-sas indicates that the disk type is SAS (high I/O).
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: csi-disk-sas # Name of the high I/O storage class, which can be customized. parameters: csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io csi.storage.k8s.io/fstype: ext4 # (Optional) Set the file system type to xfs or ext4. If it is left blank, ext4 will be used by default. everest.io/disk-volume-type: SAS # High I/O EVS disk type, which cannot be customized. everest.io/passthrough: "true" provisioner: everest-csi-provisioner reclaimPolicy: Delete volumeBindingMode: Immediate allowVolumeExpansion: true # true indicates that capacity expansion is allowed.
For an ultra-high I/O storage class, you can set the class name to csi-disk-ssd to create SSD EVS disk (ultra-high I/O).
apiVersion: storage.k8s.io/v1 kind: StorageClass metadata: name: csi-disk-ssd # Name of the ultra-high I/O storage class, which can be customized. parameters: csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io csi.storage.k8s.io/fstype: ext4 # (Optional) Set the file system type to xfs or ext4. If it is left blank, ext4 will be used by default. everest.io/disk-volume-type: SSD # Ultra-high I/O EVS disk type, which cannot be customized. everest.io/passthrough: "true" provisioner: everest-csi-provisioner reclaimPolicy: Delete volumeBindingMode: Immediate allowVolumeExpansion: true
reclaimPolicy: indicates the reclaim policies of the underlying cloud storage. The value can be Delete or Retain.
Delete: When a PVC is deleted, both the PV and the EVS disk are deleted.
Retain: When a PVC is deleted, both the PV and underlying storage resources will be retained. You need to manually delete these resources. After the PVC is deleted, the PV is in the Released state and cannot be bound to a PVC again.
If high data security is required, select Retain to prevent data from being deleted by mistake.
After the definition is complete, run the kubectl create commands to create storage resources.
# kubectl create -f sas.yaml
storageclass.storage.k8s.io/csi-disk-sas created
# kubectl create -f ssd.yaml
storageclass.storage.k8s.io/csi-disk-ssd created
Query StorageClass again. The command output is as follows:
# kubectl get sc
NAME PROVISIONER AGE
csi-disk everest-csi-provisioner 17d
csi-disk-sas everest-csi-provisioner 2m28s
csi-disk-ssd everest-csi-provisioner 16s
csi-disk-topology everest-csi-provisioner 17d
csi-nas everest-csi-provisioner 17d
csi-obs everest-csi-provisioner 17d
csi-sfsturbo everest-csi-provisioner 17d
Specifying a Default Storage Class¶
You can specify a storage class as the default class. In this way, if you do not specify storageClassName when creating a PVC, the PVC is created using the default storage class.
For example, to specify csi-disk-ssd as the default storage class, edit your YAML file as follows:
apiVersion: storage.k8s.io/v1
kind: StorageClass
metadata:
name: csi-disk-ssd
annotations:
storageclass.kubernetes.io/is-default-class: "true" # Specifies the default storage class in a cluster. A cluster can have only one default storage class.
parameters:
csi.storage.k8s.io/csi-driver-name: disk.csi.everest.io
csi.storage.k8s.io/fstype: ext4
everest.io/disk-volume-type: SSD
everest.io/passthrough: "true"
provisioner: everest-csi-provisioner
reclaimPolicy: Delete
volumeBindingMode: Immediate
allowVolumeExpansion: true
Delete the created csi-disk-ssd disk, run the kubectl create command to create a csi-disk-ssd disk again, and then query the storage class. The following information is displayed.
# kubectl delete sc csi-disk-ssd
storageclass.storage.k8s.io "csi-disk-ssd" deleted
# kubectl create -f ssd.yaml
storageclass.storage.k8s.io/csi-disk-ssd created
# kubectl get sc
NAME PROVISIONER AGE
csi-disk everest-csi-provisioner 17d
csi-disk-sas everest-csi-provisioner 114m
csi-disk-ssd (default) everest-csi-provisioner 9s
csi-disk-topology everest-csi-provisioner 17d
csi-nas everest-csi-provisioner 17d
csi-obs everest-csi-provisioner 17d
csi-sfsturbo everest-csi-provisioner 17d
Verification¶
Use csi-disk-sas to create a PVC.
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: sas-disk spec: accessModes: - ReadWriteOnce resources: requests: storage: 10Gi storageClassName: csi-disk-sas
Create a storage class and view its details. As shown below, the object can be created and the value of STORAGECLASS is csi-disk-sas.
# kubectl create -f sas-disk.yaml persistentvolumeclaim/sas-disk created # kubectl get pvc NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE sas-disk Bound pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c 10Gi RWO csi-disk-sas 24s # kubectl get pv NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c 10Gi RWO Delete Bound default/sas-disk csi-disk-sas 30s
View the PVC details on the CCE console. On the PV details page, you can see that the disk type is high I/O.
If storageClassName is not specified, the default configuration is used, as shown below.
apiVersion: v1 kind: PersistentVolumeClaim metadata: name: ssd-disk spec: accessModes: - ReadWriteOnce resources: requests: storage: 10Gi
Create and view the storage resource. You can see that the storage class of PVC ssd-disk is csi-disk-ssd, indicating that csi-disk-ssd is used by default.
# kubectl create -f ssd-disk.yaml persistentvolumeclaim/ssd-disk created # kubectl get pvc NAME STATUS VOLUME CAPACITY ACCESS MODES STORAGECLASS AGE sas-disk Bound pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c 10Gi RWO csi-disk-sas 16m ssd-disk Bound pvc-4d2b059c-0d6c-44af-9994-f74d01c78731 10Gi RWO csi-disk-ssd 10s # kubectl get pv NAME CAPACITY ACCESS MODES RECLAIM POLICY STATUS CLAIM STORAGECLASS REASON AGE pvc-4d2b059c-0d6c-44af-9994-f74d01c78731 10Gi RWO Delete Bound default/ssd-disk csi-disk-ssd 15s pvc-6e2f37f9-7346-4419-82f7-b42e79f7964c 10Gi RWO Delete Bound default/sas-disk csi-disk-sas 17m
View the PVC details on the CCE console. On the PV details page, you can see that the disk type is ultra-high I/O.