Managing storage classes

Storage class (StorageClass) allows administrators to divide the stores they provision into classes with defined parameters.

Managed Service for Kubernetes automatically provides two storage classes, yc-network-hdd and yc-network-ssd, with the following parameters:

• Volume Binding Mode: WaitForFirstConsumer.
• Reclaim Policy: Delete.
• The default class is yc-network-hdd.

These classes only let you use PersistentVolumeClaims and PersistentVolumes in access mode ReadWriteOnce.

Classes differ based on the type of disk created:

• yc-network-hdd uses a standard network drive (network-hdd).
• yc-network-ssd uses a fast network drive (network-ssd).

You can create your own storage class as well as change the default storage class.

Create a storage class

1. Save the storage class creation specification in the my-sc-hdd.yaml YAML file:

   Learn more about the storage class creation specification format.

   kind: StorageClass
   apiVersion: storage.k8s.io/v1
   metadata:
     name: my-sc-hdd
   provisioner: disk-csi-driver.mks.ycloud.io
   volumeBindingMode: WaitForFirstConsumer
   parameters:
     type: network-hdd
     csi.storage.k8s.io/fstype: ext4
   allowVolumeExpansion: false
   reclaimPolicy: Retain
   

2. Run the command:

   kubectl create -f my-sc-hdd.yaml
   

   Result:

   storageclass.storage.k8s.io/my-sc-hdd created
   

3. Check that the storage class was created:

   kubectl get storageclass
   

   Result:

   NAME                      PROVISIONER                    AGE
   my-sc-hdd                 disk-csi-driver.mks.ycloud.io  76s
   yc-network-hdd (default)  disk-csi-driver.mks.ycloud.io  16m
   yc-network-ssd            disk-csi-driver.mks.ycloud.io  16m
   

Specification format for creating a storage class

Each StorageClass object contains the provisioner, parameters, and reclaimPolicy parameters that are used for the dynamic provisioning of PersistentVolumes.

Acceptable parameter values:

• provisioner: disk-csi-driver.mks.ycloud.io.
• parameters
  • type: network-hdd or network-ssd.
  • csi.storage.k8s.io/fstype: ext2, ext3, or ext4.
• reclaimPolicy: Retain or Delete.

YAML file structure:

kind: StorageClass
apiVersion: storage.k8s.io/v1
metadata:
  name: <storage class name> # Used for accessing the storage class.
provisioner: <provisioner name>
volumeBindingMode: WaitForFirstConsumer
parameters: # Storage class parameters.
  type: <disk type>
  csi.storage.k8s.io/fstype: <file system type>
allowVolumeExpansion: false
reclaimPolicy: <reclaim policy>

Change the default storage class

1. Look up which storage class is assigned by default. default is shown next to its name in parentheses.

   kubectl get storageclass
   NAME                       PROVISIONER                     AGE
   my-sc-hdd                  disk-csi-driver.mks.ycloud.io   76s
   yc-network-hdd (default)   disk-csi-driver.mks.ycloud.io   16m
   yc-network-ssd             disk-csi-driver.mks.ycloud.io   16m
   

2. Change the storageclass.kubernetes.io/is-default-class parameter of the default storage class to false, to remove its status as the default class:

   kubectl patch storageclass yc-network-hdd \
             -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"false"}}}'
   

3. Check that yc-network-hdd is no longer the default storage class:

   kubectl get storageclass
   NAME              PROVISIONER                     AGE
   my-sc-hdd         disk-csi-driver.mks.ycloud.io   2m36s
   yc-network-hdd    disk-csi-driver.mks.ycloud.io   17m
   yc-network-ssd    disk-csi-driver.mks.ycloud.io   17m
   

4. Specify a new default storage class, such as my-sc-hdd:

   kubectl patch storageclass my-sc-hdd \
             -p '{"metadata": {"annotations":{"storageclass.kubernetes.io/is-default-class":"true"}}}'
   

5. Check that my-sc-hdd is the default storage class:

   kubectl get storageclass
   NAME                  PROVISIONER                     AGE
   my-sc-hdd (default)   disk-csi-driver.mks.ycloud.io   4m21s
   yc-network-hdd        disk-csi-driver.mks.ycloud.io   19m
   yc-network-ssd        disk-csi-driver.mks.ycloud.io   19m