Microsoft Azure Architect Design (AZ-304) Practice Test

How many instances of App1 will remain available during planned maintenance if it is run on seven Azure virtual machines in an Availability Set with three fault domains and twenty update domains?

1. 1

2. 2

3. 6

4. 7

The correct answer is: 6

The correct answer indicates that six instances of App1 will remain available during planned maintenance, and this is determined by the concepts of fault domains and update domains within an Availability Set. In Azure, an Availability Set is designed to ensure that VMs are distributed across multiple fault domains and update domains to increase availability and resilience. Fault domains represent the physical separation of underlying hardware, ensuring that VMs do not share the same power source or network switch, thereby reducing the risk of simultaneous hardware failures affecting all instances. Update domains, on the other hand, are logical groupings that allow Azure to perform maintenance on the virtual machines in a staggered manner. In this scenario, with three fault domains and twenty update domains, during planned maintenance, updates are applied to VMs across these update domains in a rolling fashion. The infrastructure ensures that not all VMs in the same fault domain are taken offline at the same time. Given that there are seven instances of App1 spread across three fault domains, at least one instance from each fault domain will remain available during updates. However, since the number of update domains significantly exceeds the number of virtual machines, it allows for many instances to stay online while others are being updated. As a result, with all update domains utilized