monitor.backfill() in datadrift tutorial is quite time consuming

Hello Microsoft Team,

I am studying datadrift monitoring and following [Azure datadrift tutorial](https://github.com/Azure/MachineLearningNotebooks/blob/master/how-to-use-azureml/work-with-data/datadrift-tutorial/datadrift-tutorial.ipynb) but when I go to `monitor.backfill()` step, it is quite time consuming to execute.

```
from azureml.widgets import RunDetails

backfill = monitor.backfill(dt.datetime.now() - dt.timedelta(weeks=6), dt.datetime.now())

RunDetails(backfill).show()
backfill.wait_for_completion()
```

As you can see in the capture picture. It have been wasting me up to 9h but have not yet completed. My baseline and target data keep the same as example and I run on compute instance with configuration:

```
Virtual machine size
Standard_DS11_v2 (4 cores, 14 GB RAM, 28 GB disk)
```
Can you explain what error happen with this example tutorial?

Comienza con datadrift-tutorial.ipynb y la celda de monitor.backfill() mostrada en el informe. Ejecuta el mismo backfill de seis semanas en la instancia de cómputo Standard_DS11_v2 indicada e inspecciona la salida de RunDetails y el comportamiento al completarse. Se considera terminado cuando se identifica por qué el backfill del tutorial no se completa en un tiempo razonable o se documenta la corrección necesaria.

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