# Volume Snapshot Classes

LLMS index: [llms.txt](/llms.txt)

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This document describes the concept of VolumeSnapshotClass in Kubernetes. Familiarity
with [volume snapshots](/docs/concepts/storage/volume-snapshots/) and
[storage classes](/docs/concepts/storage/storage-classes) is suggested.

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## 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.


<div class="alert alert-info" role="note"><h4 class="alert-heading">Note:</h4>Installation of the CRDs is the responsibility of the Kubernetes distribution.
Without the required CRDs present, the creation of a VolumeSnapshotClass fails.</div>


```yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
  name: csi-hostpath-snapclass
driver: hostpath.csi.k8s.io
deletionPolicy: Delete
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:

```yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotClass
metadata:
  name: csi-hostpath-snapclass
  annotations:
    snapshot.storage.kubernetes.io/is-default-class: "true"
driver: hostpath.csi.k8s.io
deletionPolicy: Delete
parameters:
```

If multiple CSI drivers exist, a default VolumeSnapshotClass can be specified
for each of them.

### VolumeSnapshotClass dependencies

When you create a VolumeSnapshot without specifying a VolumeSnapshotClass, Kubernetes
automatically selects a default VolumeSnapshotClass that has a CSI driver matching
the CSI driver of the PVC’s StorageClass.

This behavior allows multiple default VolumeSnapshotClass objects to coexist in a cluster, as long as
each one is associated with a unique CSI driver.

Always ensure that there is only one default VolumeSnapshotClass for each CSI driver. If
multiple default VolumeSnapshotClass objects are created using the same CSI driver,
a VolumeSnapshot creation will fail because Kubernetes cannot determine which one to use.

### 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](/docs/concepts/storage/volume-snapshots/#delete).
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`.