CSI external-snapshotter

Status and Releases

Git Repository: https://github.com/kubernetes-csi/external-snapshotter

Status: GA v4.0.0+

Supported Versions

Unsupported Versions

To use the snapshot beta and GA feature, a snapshot controller is also required. For more information, see this snapshot-controller page.

Snapshot Beta/GA

Description

The CSI external-snapshotter sidecar watches the Kubernetes API server for VolumeSnapshotContent CRD objects. The CSI external-snapshotter sidecar is also responsible for calling the CSI RPCs CreateSnapshot, DeleteSnapshot, and ListSnapshots.

Volume Group Snapshot support can be enabled with the --enable-volume-group-snapshots option. When enabled, the CSI external-snapshotter sidecar watches the API server for VolumeGroupSnapshotContent CRD object, and will be responsible for calling the CSI RPCs CreateVolumeGroupSnapshot, DeleteVolumeGroupSnapshot and GetVolumeGroupSnapshot.

VolumeSnapshotClass and VolumeGroupSnapshotClass Parameters

When provisioning a new volume snapshot, the CSI external-snapshotter sets the map<string, string> parameters field in the CSI CreateSnapshotRequest call to the key/values specified in the VolumeSnapshotClass it is handling.

When volume group snapshot support is enabled, the map<string, string> parameters field is set in the CSI CreateVolumeGroupSnapshotRequest call to the key/values specified in the VolumeGroupSnapshotClass it is handling.

The CSI external-snapshotter also reserves the parameter keys prefixed with csi.storage.k8s.io/. Any VolumeSnapshotClass or VolumeGroupSnapshotClass keys prefixed with csi.storage.k8s.io/ are not passed to the CSI driver as an opaque parameter.

The following reserved VolumeSnapshotClass parameter keys trigger behavior in the CSI external-snapshotter:

• csi.storage.k8s.io/snapshotter-secret-name (v1.0.1+)
• csi.storage.k8s.io/snapshotter-secret-namespace (v1.0.1+)
• csi.storage.k8s.io/snapshotter-list-secret-name (v2.1.0+)
• csi.storage.k8s.io/snapshotter-list-secret-namespace (v2.1.0+)

For more information on how secrets are handled see Secrets & Credentials.

VolumeSnapshot, VolumeSnapshotContent, VolumeGroupSnapshot and VolumeGroupSnapshotContent Parameters

The CSI external-snapshotter (v4.0.0+) introduces the --extra-create-metadata flag, which automatically sets the following map<string, string> parameters in the CSI CreateSnapshotRequest and CreateVolumeGroupSnapshotRequest:

• csi.storage.k8s.io/volumesnapshot/name
• csi.storage.k8s.io/volumesnapshot/namespace
• csi.storage.k8s.io/volumesnapshotcontent/name

These parameters are internally generated using the name and namespace of the source VolumeSnapshot and VolumeSnapshotContent.

For detailed snapshot beta design changes, see the design doc here.

For detailed information about volume snapshot and restore functionality, see Volume Snapshot & Restore.

Usage

CSI drivers that support provisioning volume snapshots and the ability to provision new volumes using those snapshots should use this sidecar container, and advertise the CSI CREATE_DELETE_SNAPSHOT controller capability.

CSI drivers that support provisioning volume group snapshots should use this side container too, and advertise the CSI CREATE_DELETE_GET_VOLUME_GROUP_SNAPSHOT controller capability.

For detailed information (binary parameters, RBAC rules, etc.), see https://github.com/kubernetes-csi/external-snapshotter/blob/release-6.2/README.md.

Deployment

The CSI external-snapshotter is deployed as a sidecar controller. See deployment section for more details.

For an example deployment, see this example which deploys external-snapshotter and external-provisioner with the Hostpath CSI driver.

Snapshot Alpha

Description

The CSI external-snapshotter is a sidecar container that watches the Kubernetes API server for VolumeSnapshot and VolumeSnapshotContent CRD objects.

The creation of a new VolumeSnapshot object referencing a SnapshotClass CRD object corresponding to this driver causes the sidecar container to trigger a CreateSnapshot operation against the specified CSI endpoint to provision a new snapshot. When a new snapshot is successfully provisioned, the sidecar container creates a Kubernetes VolumeSnapshotContent object to represent the new snapshot.

The deletion of a VolumeSnapshot object bound to a VolumeSnapshotContent corresponding to this driver with a delete deletion policy causes the sidecar container to trigger a DeleteSnapshot operation against the specified CSI endpoint to delete the snapshot. Once the snapshot is successfully deleted, the sidecar container also deletes the VolumeSnapshotContent object representing the snapshot.

Usage

CSI drivers that support provisioning volume snapshots and the ability to provision new volumes using those snapshots should use this sidecar container, and advertise the CSI CREATE_DELETE_SNAPSHOT controller capability.

For detailed information (binary parameters, RBAC rules, etc.), see https://github.com/kubernetes-csi/external-snapshotter/blob/release-1.2/README.md.

Deployment

The CSI external-snapshotter is deployed as a controller. See deployment section for more details.

For an example deployment, see this example which deploys external-snapshotter and external-provisioner with the Hostpath CSI driver.