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Difficulty: HardHigh Availability, Scalability, and Elasticity

A company hosts a critical web application on Azure Virtual Machine Scale Sets. To handle variable user demand, they configure autoscale rules to automatically add or remove virtual machines. All virtual machines in the scale set are deployed within a single Availability Zone. Is the statement that this design ensures high availability because the application can scale out automatically to handle traffic spikes true or false?

Answer: Answer

Answer

False
The correct answer is False because scaling out automatically (elasticity) only addresses demand fluctuations, whereas high availability requires physical redundancy across distinct failure domains (such as multiple Availability Zones) to prevent downtime from hardware or datacenter outages.

Step-by-Step Solution

1
Analyze the configuration details of the Virtual Machine Scale Set.
The scale set is configured with autoscale rules (providing elasticity/scalability) but is restricted to a single Availability Zone.
To evaluate the claim about high availability, we must separate the concepts of scale/elasticity from fault tolerance and availability zone boundaries.
2
Evaluate the impact of a zonal outage on the deployment.
If the single Availability Zone hosting the scale set experiences an outage, all virtual machine instances within that zone will become unavailable.
Availability Zones are physically separate locations within an Azure region designed to protect against datacenter failures.
3
Determine if the design achieves High Availability (HA).
Because there is a single point of failure at the zone level, the system lacks the redundancy required for High Availability, meaning the statement is false.
High availability focuses on keeping services running with minimum downtime during failures, which requires distributing resources across multiple Availability Zones or regions.

Key Concept

High Availability vs. Elasticity
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Topics

High Availability, Scalability, and Elasticity

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