Volume Snapshot Classes

This document describes the concept of VolumeSnapshotClass in Kubernetes. Familiarity with volume snapshots and storage classes is suggested.

Introduction

Just like StorageClass provides a way for administrators to describe the “classes” of storage they offer when provisioning a volume, VolumeSnapshotClass provides a way to describe the “classes” of storage when provisioning a volume snapshot.

The VolumeSnapshotClass Resource

Each VolumeSnapshotClass contains the fields driver, deletionPolicy, and parameters, which are used when a VolumeSnapshot belonging to the class needs to be dynamically provisioned.

The name of a VolumeSnapshotClass object is significant, and is how users can request a particular class. Administrators set the name and other parameters of a class when first creating VolumeSnapshotClass objects, and the objects cannot be updated once they are created.

Note: Installation of the CRDs is the responsibility of the Kubernetes distribution. Without the required CRDs present, the creation of a VolumeSnapshotClass fails.

  1. apiVersion: snapshot.storage.k8s.io/v1
  2. kind: VolumeSnapshotClass
  3. metadata:
  4.   name: csi-hostpath-snapclass
  5. driver: hostpath.csi.k8s.io
  6. deletionPolicy: Delete
  7. parameters:

Administrators can specify a default VolumeSnapshotClass for VolumeSnapshots that don’t request any particular class to bind to by adding the snapshot.storage.kubernetes.io/is-default-class: "true" annotation:

  1. apiVersion: snapshot.storage.k8s.io/v1
  2. kind: VolumeSnapshotClass
  3. metadata:
  4.   name: csi-hostpath-snapclass
  5.   annotations:
  6.     snapshot.storage.kubernetes.io/is-default-class: "true"
  7. driver: hostpath.csi.k8s.io
  8. deletionPolicy: Delete
  9. parameters:

Driver

Volume snapshot classes have a driver that determines what CSI volume plugin is used for provisioning VolumeSnapshots. This field must be specified.

DeletionPolicy

Volume snapshot classes have a deletionPolicy. It enables you to configure what happens to a VolumeSnapshotContent when the VolumeSnapshot object it is bound to is to be deleted. The deletionPolicy of a volume snapshot class can either be Retain or Delete. This field must be specified.

If the deletionPolicy is Delete, then the underlying storage snapshot will be deleted along with the VolumeSnapshotContent object. If the deletionPolicy is Retain, then both the underlying snapshot and VolumeSnapshotContent remain.

Parameters

Volume snapshot classes have parameters that describe volume snapshots belonging to the volume snapshot class. Different parameters may be accepted depending on the driver.