Understanding VM scale sets

VM scale sets are used for deploying multiple VMs at once without the need for manual actions or using scripts. You can then manage them all at once from a single place. VM scale sets are typically used to build large-scale infrastructures, where keeping all of your VMs in sync is key. The maintenance of VMs, including keeping them in sync, is handled by Azure. VM scale sets use Availability Sets under the hood. VMs inside a scale set are automatically spread over the fault and update domains by the underlying platform. VM scale sets use Azure autoscale by default. You can, however, add or remove instances yourself instead of using autoscale.

You can configure the autoscale settings to scale out (add instances) or in (reduce the number of instances) based on CPU thresholds. For example, you can create a rule to add additional instances if the CPU threshold is over 80% for 5 minutes. You can then have the scale set scaled back if the CPU threshold drops...