Merge pull request #295646 from seligj95/patch-3

add temporary note about 2AZ stamps

Author: prmerger-automator[bot]

articles/reliability/reliability-app-service.md

@@ -62,6 +62,10 @@ Instance spreading with a zone-redundant deployment is determined using the foll
 - The instances spread evenly if you specify a capacity larger than three, and the number of instances is divisible by three.
 - Any instance counts beyond 3*N are spread across the remaining one or two zones.
 
+> [!NOTE]
+> In some cases, your workload is hosted on a [scale unit](/azure/app-service/overview-hosting-plans#how-does-my-app-run-and-scale) (also known as a stamp or VMSS compute cluster) that is deployed across two zones rather than three zones. For these cases, the instances are evenly spread across the two zones if the number of instances is divisible by two. Any instance count beyond 2*n is placed in one of the zones. 
+> 
+
 When the App Service platform allocates instances for a zone-redundant App Service plan, it uses best effort zone balancing offered by the underlying Azure virtual machine scale sets. An App Service plan is *balanced* if each zone has either the same number of virtual machines, or plus or minus one, in all of the other zones. For more information, see [Zone balancing](/azure/virtual-machine-scale-sets/virtual-machine-scale-sets-use-availability-zones#zone-balancing).
 
 For App Service plans that aren't configured as zone redundant, virtual machine instances aren't resilient to availability zone failures. They can experience downtime during an outage in any zone in that region.