---
title: 卷快照
content_type: concept
weight: 60
---
<!--
reviewers:
- saad-ali
- thockin
- msau42
- jingxu97
- xing-yang
- yuxiangqian
title: Volume Snapshots
content_type: concept
weight: 60
-->

<!-- overview -->

<!--
In Kubernetes, a _VolumeSnapshot_ represents a snapshot of a volume on a storage
system. This document assumes that you are already familiar with Kubernetes
[persistent volumes](/docs/concepts/storage/persistent-volumes/).
-->
在 Kubernetes 中，**卷快照** 是一个存储系统上卷的快照，本文假设你已经熟悉了 Kubernetes
的[持久卷](/zh-cn/docs/concepts/storage/persistent-volumes/)。

<!-- body -->

<!--
## Introduction
-->
## 介绍 {#introduction}

<!--
Similar to how API resources `PersistentVolume` and `PersistentVolumeClaim` are
used to provision volumes for users and administrators, `VolumeSnapshotContent`
and `VolumeSnapshot` API resources are provided to create volume snapshots for
users and administrators.
-->
与 `PersistentVolume` 和 `PersistentVolumeClaim` 这两个 API 资源用于给用户和管理员制备卷类似，
`VolumeSnapshotContent` 和 `VolumeSnapshot` 这两个 API 资源用于给用户和管理员创建卷快照。

<!--
A `VolumeSnapshotContent` is a snapshot taken from a volume in the cluster that
has been provisioned by an administrator. It is a resource in the cluster just
like a PersistentVolume is a cluster resource.
-->
`VolumeSnapshotContent` 是从一个卷获取的一种快照，该卷由管理员在集群中进行制备。
就像持久卷（PersistentVolume）是集群的资源一样，它也是集群中的资源。

<!--
A `VolumeSnapshot` is a request for snapshot of a volume by a user. It is similar
to a PersistentVolumeClaim.
-->
`VolumeSnapshot` 是用户对于卷的快照的请求。它类似于持久卷声明（PersistentVolumeClaim）。

<!--
`VolumeSnapshotClass` allows you to specify different attributes belonging to a
`VolumeSnapshot`. These attributes may differ among snapshots taken from the same
volume on the storage system and therefore cannot be expressed by using the same
`StorageClass` of a `PersistentVolumeClaim`.
-->
`VolumeSnapshotClass` 允许指定属于 `VolumeSnapshot` 的不同属性。在从存储系统的相同卷上获取的快照之间，
这些属性可能有所不同，因此不能通过使用与 `PersistentVolumeClaim` 相同的 `StorageClass` 来表示。

<!--
Volume snapshots provide Kubernetes users with a standardized way to copy a volume's
contents at a particular point in time without creating an entirely new volume. This
functionality enables, for example, database administrators to backup databases before
performing edit or delete modifications.
-->
卷快照能力为 Kubernetes 用户提供了一种标准的方式来在指定时间点复制卷的内容，并且不需要创建全新的卷。
例如，这一功能使得数据库管理员能够在执行编辑或删除之类的修改之前对数据库执行备份。

<!--
Users need to be aware of the following when using this feature:
-->
当使用该功能时，用户需要注意以下几点：

<!--
- API Objects `VolumeSnapshot`, `VolumeSnapshotContent`, and `VolumeSnapshotClass`
  are {{< glossary_tooltip term_id="CustomResourceDefinition" text="CRDs" >}}, not
  part of the core API.
- `VolumeSnapshot` support is only available for CSI drivers.
- As part of the deployment process of `VolumeSnapshot`, the Kubernetes team provides
  a snapshot controller to be deployed into the control plane, and a sidecar helper
  container called csi-snapshotter to be deployed together with the CSI driver.
  The snapshot controller watches `VolumeSnapshot` and `VolumeSnapshotContent` objects
  and is responsible for the creation and deletion of `VolumeSnapshotContent` object.
  The sidecar csi-snapshotter watches `VolumeSnapshotContent` objects and triggers
  `CreateSnapshot` and `DeleteSnapshot` operations against a CSI endpoint.
- There is also a validating webhook server which provides tightened validation on
  snapshot objects. This should be installed by the Kubernetes distros along with
  the snapshot controller and CRDs, not CSI drivers. It should be installed in all
  Kubernetes clusters that has the snapshot feature enabled.
- CSI drivers may or may not have implemented the volume snapshot functionality.
  The CSI drivers that have provided support for volume snapshot will likely use
  the csi-snapshotter. See [CSI Driver documentation](https://kubernetes-csi.github.io/docs/) for details.
- The CRDs and snapshot controller installations are the responsibility of the Kubernetes distribution.
-->
- API 对象 `VolumeSnapshot`，`VolumeSnapshotContent` 和 `VolumeSnapshotClass`
  是 {{< glossary_tooltip term_id="CustomResourceDefinition" text="CRD" >}}，
  不属于核心 API。
- `VolumeSnapshot` 支持仅可用于 CSI 驱动。
- 作为 `VolumeSnapshot` 部署过程的一部分，Kubernetes 团队提供了一个部署于控制平面的快照控制器，
  并且提供了一个叫做 `csi-snapshotter` 的边车（Sidecar）辅助容器，和 CSI 驱动程序一起部署。
  快照控制器监视 `VolumeSnapshot` 和 `VolumeSnapshotContent` 对象，
  并且负责创建和删除 `VolumeSnapshotContent` 对象。
  边车 csi-snapshotter 监视 `VolumeSnapshotContent` 对象，
  并且触发针对 CSI 端点的 `CreateSnapshot` 和 `DeleteSnapshot` 的操作。
- 还有一个验证性质的 Webhook 服务器，可以对快照对象进行更严格的验证。
  Kubernetes 发行版应将其与快照控制器和 CRD（而非 CSI 驱动程序）一起安装。
  此服务器应该安装在所有启用了快照功能的 Kubernetes 集群中。
- CSI 驱动可能实现，也可能没有实现卷快照功能。CSI 驱动可能会使用 csi-snapshotter
  来提供对卷快照的支持。详见 [CSI 驱动程序文档](https://kubernetes-csi.github.io/docs/)
- Kubernetes 负责 CRD 和快照控制器的安装。

<!--
For advanced use cases, such as creating group snapshots of multiple volumes, see the external
[CSI Volume Group Snapshot documentation](https://kubernetes-csi.github.io/docs/group-snapshot-restore-feature.html).
-->
对于高级用例，例如创建多个卷的组快照，请参阅外部
[CSI 卷组快照文档](https://kubernetes-csi.github.io/docs/group-snapshot-restore-feature.html)。

<!--
## Lifecycle of a volume snapshot and volume snapshot content

`VolumeSnapshotContents` are resources in the cluster. `VolumeSnapshots` are requests
for those resources. The interaction between `VolumeSnapshotContents` and `VolumeSnapshots`
follow this lifecycle:
-->
## 卷快照和卷快照内容的生命周期 {#lifecycle-of-a-volume-snapshot-and-volume-snapshot-content}

`VolumeSnapshotContents` 是集群中的资源。`VolumeSnapshots` 是对于这些资源的请求。
`VolumeSnapshotContents` 和 `VolumeSnapshots` 之间的交互遵循以下生命周期：

<!--
### Provisioning Volume Snapshot

There are two ways snapshots may be provisioned: pre-provisioned or dynamically provisioned.
-->
### 制备卷快照 {#provisioning-volume-snapshot}

快照可以通过两种方式进行制备：预制备或动态制备。

<!--
#### Pre-provisioned {#static}

A cluster administrator creates a number of `VolumeSnapshotContents`. They carry the details
of the real volume snapshot on the storage system which is available for use by cluster users.
They exist in the Kubernetes API and are available for consumption.
-->
#### 预制备 {#static}

集群管理员创建多个 `VolumeSnapshotContents`。它们带有存储系统上实际卷快照的详细信息，可以供集群用户使用。
它们存在于 Kubernetes API 中，并且能够被使用。

<!--
#### Dynamic

Instead of using a pre-existing snapshot, you can request that a snapshot to be dynamically
taken from a PersistentVolumeClaim. The [VolumeSnapshotClass](/docs/concepts/storage/volume-snapshot-classes/)
specifies storage provider-specific parameters to use when taking a snapshot.
-->
#### 动态制备 {#dynamic}

可以从 `PersistentVolumeClaim` 中动态获取快照，而不用使用已经存在的快照。
在获取快照时，[卷快照类](/zh-cn/docs/concepts/storage/volume-snapshot-classes/)
指定要用的特定于存储提供程序的参数。

<!--
### Binding

The snapshot controller handles the binding of a `VolumeSnapshot` object with an appropriate
`VolumeSnapshotContent` object, in both pre-provisioned and dynamically provisioned scenarios.
The binding is a one-to-one mapping.
-->
### 绑定 {#binding}

在预制备和动态制备场景下，快照控制器处理绑定 `VolumeSnapshot` 对象和其合适的 `VolumeSnapshotContent` 对象。
绑定关系是一对一的。

<!--
In the case of pre-provisioned binding, the VolumeSnapshot will remain unbound until the
requested VolumeSnapshotContent object is created.
-->
在预制备快照绑定场景下，`VolumeSnapshotContent` 对象创建之后，才会和 `VolumeSnapshot` 进行绑定。

<!--
### Persistent Volume Claim as Snapshot Source Protection

The purpose of this protection is to ensure that in-use
{{< glossary_tooltip text="PersistentVolumeClaim" term_id="persistent-volume-claim" >}}
API objects are not removed from the system while a snapshot is being taken from it
(as this may result in data loss).
-->
### 快照源的持久性卷声明保护   {#persistent-volume-claim-as-snapshot-source-protection}

这种保护的目的是确保在从系统中获取快照时，不会将正在使用的
{{< glossary_tooltip text="PersistentVolumeClaim" term_id="persistent-volume-claim" >}}
API 对象从系统中删除（因为这可能会导致数据丢失）。

<!--
While a snapshot is being taken of a PersistentVolumeClaim, that PersistentVolumeClaim
is in-use. If you delete a PersistentVolumeClaim API object in active use as a snapshot
source, the PersistentVolumeClaim object is not removed immediately. Instead, removal of
the PersistentVolumeClaim object is postponed until the snapshot is readyToUse or aborted.
-->
在为某 `PersistentVolumeClaim` 生成快照时，该 `PersistentVolumeClaim` 处于被使用状态。
如果删除一个正作为快照源使用的 `PersistentVolumeClaim` API 对象，该 `PersistentVolumeClaim` 对象不会立即被移除。
相反，移除 `PersistentVolumeClaim` 对象的动作会被推迟，直到快照状态变为 ReadyToUse 或快照操作被中止时再执行。

<!--
### Delete

Deletion is triggered by deleting the `VolumeSnapshot` object, and the `DeletionPolicy`
will be followed. 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.
-->
### 删除 {#delete}

删除 `VolumeSnapshot` 对象触发删除 `VolumeSnapshotContent` 操作，并且 `DeletionPolicy` 会紧跟着执行。
如果 `DeletionPolicy` 是 `Delete`，那么底层存储快照会和 `VolumeSnapshotContent` 一起被删除。
如果 `DeletionPolicy` 是 `Retain`，那么底层快照和 `VolumeSnapshotContent` 都会被保留。

<!--
## VolumeSnapshots

Each VolumeSnapshot contains a spec and a status.
-->
## 卷快照 {#volume-snapshots}

每个 `VolumeSnapshot` 包含一个 spec 和一个 status。

```yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: new-snapshot-test
spec:
  volumeSnapshotClassName: csi-hostpath-snapclass
  source:
    persistentVolumeClaimName: pvc-test
```

<!--
`persistentVolumeClaimName` is the name of the PersistentVolumeClaim data source
for the snapshot. This field is required for dynamically provisioning a snapshot.

A volume snapshot can request a particular class by specifying the name of a
[VolumeSnapshotClass](/docs/concepts/storage/volume-snapshot-classes/)
using the attribute `volumeSnapshotClassName`. If nothing is set, then the
default class is used if available.
-->
`persistentVolumeClaimName` 是 `PersistentVolumeClaim` 数据源对快照的名称。
这个字段是动态制备快照中的必填字段。

卷快照可以通过指定 [VolumeSnapshotClass](/zh-cn/docs/concepts/storage/volume-snapshot-classes/)
使用 `volumeSnapshotClassName` 属性来请求特定类。如果没有设置，那么使用默认类（如果有）。

<!--
For pre-provisioned snapshots, you need to specify a `volumeSnapshotContentName`
as the source for the snapshot as shown in the following example. The
`volumeSnapshotContentName` source field is required for pre-provisioned snapshots.
-->
如下面例子所示，对于预制备的快照，需要给快照指定 `volumeSnapshotContentName` 作为来源。
对于预制备的快照 `source` 中的`volumeSnapshotContentName` 字段是必填的。

```yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshot
metadata:
  name: test-snapshot
spec:
  source:
    volumeSnapshotContentName: test-content
```

<!--
## Volume Snapshot Contents

Each VolumeSnapshotContent contains a spec and status. In dynamic provisioning,
the snapshot common controller creates `VolumeSnapshotContent` objects. Here is an example:
-->
## 卷快照内容   {#volume-snapshot-contents}

每个 VolumeSnapshotContent 对象包含 spec 和 status。
在动态制备时，快照通用控制器创建 `VolumeSnapshotContent` 对象。下面是例子：

```yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotContent
metadata:
  name: snapcontent-72d9a349-aacd-42d2-a240-d775650d2455
spec:
  deletionPolicy: Delete
  driver: hostpath.csi.k8s.io
  source:
    volumeHandle: ee0cfb94-f8d4-11e9-b2d8-0242ac110002
  sourceVolumeMode: Filesystem
  volumeSnapshotClassName: csi-hostpath-snapclass
  volumeSnapshotRef:
    name: new-snapshot-test
    namespace: default
    uid: 72d9a349-aacd-42d2-a240-d775650d2455
```

<!--
`volumeHandle` is the unique identifier of the volume created on the storage
backend and returned by the CSI driver during the volume creation. This field
is required for dynamically provisioning a snapshot.
It specifies the volume source of the snapshot.

For pre-provisioned snapshots, you (as cluster administrator) are responsible
for creating the `VolumeSnapshotContent` object as follows.
-->
`volumeHandle` 是存储后端创建卷的唯一标识符，在卷创建期间由 CSI 驱动程序返回。
动态设置快照需要此字段。它指出了快照的卷源。

对于预制备快照，你（作为集群管理员）要按如下命令来创建 `VolumeSnapshotContent` 对象。

```yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotContent
metadata:
  name: new-snapshot-content-test
spec:
  deletionPolicy: Delete
  driver: hostpath.csi.k8s.io
  source:
    snapshotHandle: 7bdd0de3-aaeb-11e8-9aae-0242ac110002
  sourceVolumeMode: Filesystem
  volumeSnapshotRef:
    name: new-snapshot-test
    namespace: default
```

<!--
`snapshotHandle` is the unique identifier of the volume snapshot created on
the storage backend. This field is required for the pre-provisioned snapshots.
It specifies the CSI snapshot id on the storage system that this
`VolumeSnapshotContent` represents.
-->
`snapshotHandle` 是存储后端创建卷的唯一标识符。对于预制备的快照，这个字段是必需的。
它指定此 `VolumeSnapshotContent` 表示的存储系统上的 CSI 快照 ID。

<!--
`sourceVolumeMode` is the mode of the volume whose snapshot is taken. The value
of the `sourceVolumeMode` field can be either `Filesystem` or `Block`. If the
source volume mode is not specified, Kubernetes treats the snapshot as if the
source volume's mode is unknown.
-->
`sourceVolumeMode` 是创建快照的卷的模式。`sourceVolumeMode` 字段的值可以是
`Filesystem` 或 `Block`。如果没有指定源卷模式，Kubernetes 会将快照视为未知的源卷模式。

<!--
`volumeSnapshotRef` is the reference of the corresponding `VolumeSnapshot`. Note that
when the `VolumeSnapshotContent` is being created as a pre-provisioned snapshot, the
`VolumeSnapshot` referenced in `volumeSnapshotRef` might not exist yet.
-->
`volumeSnapshotRef` 字段是对相应的 `VolumeSnapshot` 的引用。
请注意，当 `VolumeSnapshotContent` 被创建为预配置快照时。
`volumeSnapshotRef` 中引用的 `VolumeSnapshot` 可能还不存在。

<!--
## Converting the volume mode of a Snapshot {#convert-volume-mode}

If the `VolumeSnapshots` API installed on your cluster supports the `sourceVolumeMode`
field, then the API has the capability to prevent unauthorized users from converting
the mode of a volume.

To check if your cluster has capability for this feature, run the following command:
-->
## 转换快照的卷模式 {#convert-volume-mode}

如果在你的集群上安装的 `VolumeSnapshots` API 支持 `sourceVolumeMode`
字段，则该 API 可以防止未经授权的用户转换卷的模式。

要检查你的集群是否具有此特性的能力，可以运行如下命令：

```shell
kubectl get crd volumesnapshotcontent -o yaml
```

<!--
If you want to allow users to create a `PersistentVolumeClaim` from an existing
`VolumeSnapshot`, but with a different volume mode than the source, the annotation
`snapshot.storage.kubernetes.io/allow-volume-mode-change: "true"`needs to be added to
the `VolumeSnapshotContent` that corresponds to the `VolumeSnapshot`.
-->
如果你希望允许用户从现有的 `VolumeSnapshot` 创建 `PersistentVolumeClaim`，
但是使用与源卷不同的卷模式，则需要添加注解
`snapshot.storage.kubernetes.io/allow-volume-mode-change: "true"`
到对应 `VolumeSnapshot` 的 `VolumeSnapshotContent` 中。

<!--
For pre-provisioned snapshots, `spec.sourceVolumeMode` needs to be populated
by the cluster administrator.

An example `VolumeSnapshotContent` resource with this feature enabled would look like:
-->
对于预制备的快照，`spec.sourceVolumeMode` 需要由集群管理员填充。

启用此特性的 `VolumeSnapshotContent` 资源示例如下所示：

```yaml
apiVersion: snapshot.storage.k8s.io/v1
kind: VolumeSnapshotContent
metadata:
  name: new-snapshot-content-test
  annotations:
    - snapshot.storage.kubernetes.io/allow-volume-mode-change: "true"
spec:
  deletionPolicy: Delete
  driver: hostpath.csi.k8s.io
  source:
    snapshotHandle: 7bdd0de3-aaeb-11e8-9aae-0242ac110002
  sourceVolumeMode: Filesystem
  volumeSnapshotRef:
    name: new-snapshot-test
    namespace: default
```

<!--
## Provisioning Volumes from Snapshots
-->
## 从快照制备卷 {#provisioning-volumes-from-snapshots}

<!--
You can provision a new volume, pre-populated with data from a snapshot, by using
the _dataSource_ field in the `PersistentVolumeClaim` object.
-->
你可以制备一个新卷，该卷预填充了快照中的数据，在 `PersistentVolumeClaim` 对象中使用 **dataSource** 字段。

<!--
For more details, see
[Volume Snapshot and Restore Volume from Snapshot](/docs/concepts/storage/persistent-volumes/#volume-snapshot-and-restore-volume-from-snapshot-support).
-->
更多详细信息，
请参阅[卷快照和从快照还原卷](/zh-cn/docs/concepts/storage/persistent-volumes/#volume-snapshot-and-restore-volume-from-snapshot-support)。