Box 1: 3 -
Need three host groups to meet the third scenario requirement below.
Scenario: App1 must meet the following requirements:
Be hosted in an Azure region that supports availability zones.
Be hosted on Azure virtual machines that support automatic scaling.
Maintain availability if two availability zones in the local Azure region fail.
Box 2: 3 -
The availability setting of your host group should match your scale set.
* The host group and the scale set must be using the same availability zone.
* The fault domain count for the host group level should match the fault domain count for your scale set.
Reference:
https://docs.microsoft.com/en-us/azure/virtual-machines/dedicated-hosts
