VM backup restore use Longhorn v1.5+ attach/detach mechanism

• Related issues: #4907 [ENHANCEMENT] Take advantage of the attach/detach mechanism in Longhorn v1.5+

Category:

• Backup and Restore

Verification Steps

Case 1: snapshot can work on a stopped VM.

• This test have already been covered in e2e backend automation of test plan
  • test_restore_from_vm_snapshot_while_pvc_detached_from_source in test_4_vm_snapshot.py L457-L487

Case 2: restore a snapshot from detached volumes can work.

• This test have already been covered in e2e backend automation of test plan
  • test_create_vm_snapshot_while_pvc_detached in test_4_vm_snapshot.py L425-L453

Case 3: backup can work on a stopped VM

1. Create a VM.
2. After the VM is ready, stop the VM.
3. Check VM volumes are detached.
4. Take a backup on the VM. The backup can be ready.

Case 4: race condition doesn’t break VMBackup

1. Create a VM.
2. After the VM is ready, stop the VM.
3. Check VM volumes are detached.
4. Take multiple backup on the VM in a short time. All backup can be ready.

Case 5: restore a backup from detached volumes can work:

1. Follow Case 3.
2. Make sure VM volumes are detached.
3. Restore the backup to a new VM. The new VM can be ready.
4. Restore the backup to replace the old VM. The old VM can be ready.

Expected Results

• Case 1: snapshot can work on a stopped VM

  • VM volumes are detached after we stop VM.

    node1:~ # kubectl get volume -A
    NAMESPACE         NAME                                       STATE      ROBUSTNESS   SCHEDULED   SIZE          NODE   AGE
    longhorn-system   pvc-5a861225-920d-4059-b501-f02b2fd0ff27   detached   unknown                  10737418240          19m
    

  • Take the vm snapshot, The snapshot of vm in off state can be ready.

• Case 2: restore a snapshot from detached volumes can work.

  • Restore the snapshot to a new VM. The new VM can be ready.
  • Restore the snapshot to replace the old VM. The old VM can be ready.

• Case 3: backup can work on a stopped VM.

  • VM volumes are detached after we stop VM.

    NAMESPACE         NAME                                       STATE      ROBUSTNESS   SCHEDULED   SIZE          NODE   AGE
    longhorn-system   pvc-d1226d97-ab90-4d40-92f9-960b668093c2   detached   unknown                  10737418240          5m12s
    

  • Take the vm backup, The backup of vm in off state can be ready.

• Case 4: race condition doesn’t break VMBackup

  • Take multiple backup on the VM in a short time. All backup can be ready.

• Case 5: restore a backup from detached volumes can work

  • Restore the backup to a new VM. The new VM can be ready.
  • Restore the backup to replace the old VM. (Retain Volume), The old VM can be ready.
  • Restore the backup to replace the old VM. (Delete Volume), The old VM can be ready.