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

3. Check that the storage class was created:

   $ 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
   

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