AZ-305 Question 133
Select 2You are designing a mission-critical web application hosted on Azure Virtual Machines. The application must remain available during both planned maintenance and unplanned hardware failures in the same region. Which two solutions should you implement to maximize high availability for the compute tier?
- A
Deploy multiple Azure VMs in a single Availability Set and place them behind an Azure Load Balancer.
- B
Use a single Azure VM in an Availability Zone-based Scale Set.
- C
Deploy Azure VMs across multiple Availability Zones and place them behind an Azure Load Balancer or Application Gateway.
- D
Use Azure Site Recovery to replicate a single VM to another region for automatic failover.
Show answer and explanation
Correct answers: A, C
Explanation
To ensure maximum uptime in a single Azure region, you should deploy at least two VMs across different fault/update domains (with an Availability Set) or availability zones, then place them behind a load balancer to distribute traffic. This approach protects against both planned maintenance and unexpected hardware failures. For more information, see Microsoft’s documentation on creating highly available Azure VMs: https://learn.microsoft.com/azure/virtual-machines/availability-overview.
- A. Correct.
Option 1: Correct. Placing multiple VMs in an Availability Set spreads them across fault and update domains, ensuring at least one VM remains operational during maintenance or hardware failures. Combining this with an Azure Load Balancer provides traffic distribution and further resiliency.
- B. Incorrect.
Option 2: Incorrect. A single VM in a Scale Set, even if using an Availability Zone, cannot ensure high availability if the zone experiences an outage. At least two instances in different zones are needed for zone-level resiliency.
- C. Correct.
Option 3: Correct. Distributing VMs across multiple Availability Zones protects against zone-wide failures. Using an Azure Load Balancer or Application Gateway helps balance traffic and ensures that requests are routed to healthy VMs.
- D. Incorrect.
Option 4: Incorrect. Azure Site Recovery primarily addresses disaster recovery between regions, not day-to-day high availability within the same region. Relying on this alone won't protect against local hardware or maintenance events.