Velero snapshot metadata during data upload

[hasethuraman]

Hi,

I see that we delete the CSI snapshots while moving the data. Also I see we create the backup volume snapshot and content during backup-pvc creation for moving the data.

1. So the backup volume pvc & snapshot that we have created here will also be backed up ?
2. What happens to the existing pvc metadata?
3. Lets say, if we backup snapshot metadata (but not backup-pvc) in (1) and existing-pvc metadata will be backed up in (2), during restore how do we know that this snapshot metadata is for this existing backed up pvc?

Apologize, if my question is not clear

[hasethuraman]

In fact I see that we delete the backup objects at the end of data upload completion. I am wondering now, that we dont have snapshot metadata at all?

func (e *csiSnapshotExposer) CleanUp(ctx context.Context, ownerObject corev1.ObjectReference, vsName string, sourceNamespace string) {
	backupPodName := ownerObject.Name
	backupPVCName := ownerObject.Name
	backupVSName := ownerObject.Name

	kube.DeletePodIfAny(ctx, e.kubeClient.CoreV1(), backupPodName, ownerObject.Namespace, e.log)
	kube.DeletePVAndPVCIfAny(ctx, e.kubeClient.CoreV1(), backupPVCName, ownerObject.Namespace, cleanUpTimeout, e.log)

	csi.DeleteVolumeSnapshotIfAny(ctx, e.csiSnapshotClient, backupVSName, ownerObject.Namespace, e.log)
	csi.DeleteVolumeSnapshotIfAny(ctx, e.csiSnapshotClient, vsName, sourceNamespace, e.log)
}

In Expose() of csi_snapshot.go, I see this which deletes the original metadata?

	err = csi.EnsureDeleteVS(ctx, e.csiSnapshotClient, volumeSnapshot.Name, volumeSnapshot.Namespace, csiExposeParam.OperationTimeout)
	err = csi.EnsureDeleteVSC(ctx, e.csiSnapshotClient, vsc.Name, csiExposeParam.OperationTimeout)

Does it mean we are left only with data moved? I am missing something and could not understand how we know during that this data is for this pvc.

[blackpiglet]

This design document may help understand how the CSI snapshot data movement works.
https://github.com/vmware-tanzu/velero/blob/main/design/Implemented/volume-snapshot-data-movement/volume-snapshot-data-movement.md

The DataUpload has information to reference the target Pod and PVC.

[hasethuraman]

Thanks for the doc reference. I am going through that doc still (as well as code) but I am not sure if I am missing to infer the below question

1. I have the volume snapshot in k8s cluster and has handle - 'X'
2. Now as part of data mover, I moved it to a different location - 'Y'
3. Now, I believe we cant update the volume snapshot content metadata to have the new handle - 'Y'. Or should data mover supposed to create a new snapshot metadata and delete old one? Or data mover to handover 'Y' information to velero which will take care of updating existing metadata.
4. After the backup, can the snapshot metadata have 'Y'

[blackpiglet]

The CSI snapshot data mover assumes the backup and restore environments can share the snapshots to work.
For your mentioned scenario, I think the CSI snapshot data mover cannot work.
The filesystem backup should be choosed: https://velero.io/docs/v1.15/file-system-backup/