protected override async Task RunAsync(CancellationToken cancellationToken)
{
  // ...

  while (true)
  {
    cancellationToken.ThrowIfCancellationRequested();
    BackupDescription myBackupDescription = new BackupDescription(BackupOption.Full, this.BackupCallbackAsync);
    await this.BackupAsync(myBackupDescription);

    // ...

    await Task.Delay(TimeSpan.FromSeconds(1), cancellationToken);
  }
}

private async Task<bool> BackupCallbackAsync(BackupInfo backupInfo, CancellationToken cancellationToken)
{
  var backupId = Guid.NewGuid();
  // backup files copied to external storage here ...
  return true;
}

Connect-ServiceFabricCluster
$s = "fabric:/WebReferenceApplication/InventoryService"
$p = Get-ServiceFabricApplication | Get-ServiceFabricService -ServiceName $s | Get-ServiceFabricPartition | Select -First 1
$p | Invoke-ServiceFabricPartitionDataLoss -DataLossMode FullDataLoss -ServiceName $s