VolumeSnapshot Using KubeStash

This guide will give you an overview of how VolumeSnapshot process works in KubeStash.

How Backup Process Works?

The following diagram shows how KubeStash creates VolumeSnapshot via Kubernetes native API. Open the image in a new tab to see the enlarged version.

  

The VolumeSnapshot process consists of the following steps:

1. At first, a user creates a Secret with access credentials of the backend where the backed-up data will be stored.

2. Then, she creates a BackupStorage custom resource that specifies the backend information, along with the Secret containing the credentials needed to access the backend.

3. KubeStash operator watches for BackupStorage custom resources. When it finds a BackupStorage object, it initializes the BackupStorage by uploading the metadata.yaml file to the target storage.

4. Then, she creates a BackupConfiguration custom resource that specifies the targeted workload/PVC, the Addon info with a specified task, etc. It also provides information about one or more repositories, each indicating a path and a BackupStorage for storing the metadata.

5. KubeStash operator watches for BackupConfiguration custom resources.

6. Once the KubeStash operator finds a BackupConfiguration object, it creates Repository with the information specified in the BackupConfiguration.

7. KubeStash operator watches for Repository custom resources. When it finds the Repository object, it Initializes Repository by uploading repository.yaml file to the spec.sessions[*].repositories[*].directory path specified in the BackupConfiguration.

8. Then, it creates a CronJob with the schedule specified in BackupConfiguration to trigger backup periodically.

9. On the next scheduled slot, the CronJob triggers a backup by creating a BackupSession custom resource.

10. KubeStash operator watches for BackupSession custom resources.

11. When it finds a BackupSession object, it creates a Snapshot custom resource for each Repository specified in the respective session of the BackupConfiguration.

12. Then, it resolves the respective Addon and Function and prepares a volume snapshotter Job definition.

13. Then, It creates a volume snapshotter Job to capture snapshots of the targeted volumes.

14. The volume snapshotter Job creates a VolumeSnapshot(s) object for each Persistent Volume Claims (PVC) associated the target and waits for the Container Storage Interface (CSI) driver to complete snapshotting. The VolumeSnapshot(s) are created with the following naming format:

      <PVC name>-<BackupSession creation timestamp in Unix epoch seconds>
    

15. Container Storage Interface (CSI) external-snapshotter controller watches for VolumeSnapshot resources.

16. When it finds a VolumeSnapshot object, it backups VolumeSnapshot to the respective cloud storage.

17. After the snapshotting process is completed, the volume snapshotter Job updates the status.components[*] field of the Snapshot resources withVolumeSnapshot information.

How Restore Process Works?

The following diagram shows how KubeStash restores PersistentVolumeClaims from snapshot using Kubernetes VolumeSnapshot API. Open the image in a new tab to see the enlarged version.

  

The restore process consists of the following steps:

1. At first, a user creates a RestoreSession custom resource that specifies the volumeClaimTemplates, Addon info with a specified task, and a DataSource that determines the Snapshot from which the data will be restored.

2. KubeStash operator watches for RestoreSession custom resources.

3. Once it finds a RestoreSession object, it resolves the respective Addon and Function and prepares a restore Job definition.

4. Then, it creates a Restore Job to restore PVC from the volumeSnapshot.

5. The restore job retrieves VolumeSnapshot information from the Snapshot. It starts by creating PVCs based on volumeClaimTemplates and assigns the corresponding VolumeSnapshot name to the spec.dataSourceRef of each PVC.

6. Container Storage Interface (CSI) external-snapshotter controller watches for PVCs.

7. When it finds a new PVC with spec.dataSource field set, it reads the information about the VolumeSnapshot.

8. The controller downloads the respective data from the cloud and populates the PVC.

9. Once completed, the job updates the status.components[*] field of the Restoresession to reflect restore completion.

Next Steps

1. See a step by step guide to snapshot a stand-alone PVC here.
2. See a step by step guide to snapshot the volumes of a Deployment here.
3. See a step by step guide to snapshot the volumes of a StatefulSet here.