Velero with Longhorn CSI snapshot support

[ehemmerlin]

We are currently using Velero's Container Storage Interface (CSI) snapshot support and it's CSI volume data movement feature. connected to Longhorn storage which supports CSI snapshots.

The issue we face is that the backups use a lot of disk space, as Longhorn replicates the data of each snapshot the same way it does for all of our Kubernetes volumes. Moreover it retains these volumes, as it's the default behaviour of our storage class, so volumes created during backups are never deleted even if the backup has expired and no longer exists.

We are looking for a way to remove the volumes created by the snapshots after the backup is deleted: is there a way to specify a different storage class for Velero's backup (we could create one with a Delete reclaim policy instead of a Retain one) or another way to solve this issue and delete the volumes from expired backups?

[MartMet]

You need to provide a VolumeSnapshotClass with a special parameter so longhorn can decide its a "longhorn-backup" or "longhorn-snapshot" - both can be snapshotted via CSI but backups will remain, while snapshots will be deleted. Detailed explanation

volumesnapshotclass.yaml

kind: VolumeSnapshotClass
apiVersion: snapshot.storage.k8s.io/v1
metadata:
  name: longhorn-backup-vsc
  labels:
    velero.io/csi-volumesnapshot-class: "true"
driver: driver.longhorn.io
deletionPolicy: Delete
parameters:
  type: snap

[blackpiglet]

Users have several choices when selecting VolumeSnapshotClass in the Velero CSI backup.
Please check this document for details:
https://velero.io/docs/v1.14/csi/#implementation-choices

[ehemmerlin]

Thank you @MartMet and @blackpiglet for your answers. @blackpiglet you are right, as VolumeSnapshots created by the Velero CSI plugins are retained only for the lifetime of the backup even if the DeletionPolicy on the VolumeSnapshotClass is set to Retain, the issue we had is fixed and this question can be closed.

Congratulations to the Velero team for the good work done!

VolumeSnapshots created by the Velero CSI plugins are retained only for the lifetime of the backup even if the DeletionPolicy on the VolumeSnapshotClass is set to Retain. To accomplish this, during deletion of the backup the prior to deleting the VolumeSnapshot, VolumeSnapshotContent object is patched to set its DeletionPolicy to Delete. Deleting the VolumeSnapshot object will result in cascade delete of the VolumeSnapshotContent and the snapshot in the storage provider.

Quoted from: https://velero.io/docs/main/csi/#implementation-choices