The answer is an Availability Set. This is the correct choice because an Availability Set logically groups Azure VMs to protect against failures within a single datacenter by distributing them across multiple fault domains—separate racks with independent power, cooling, and network—and update domains, ensuring that if one VM fails due to hardware issues or planned maintenance, another VM in a different fault domain continues serving users. On the Microsoft Azure Fundamentals AZ-900 exam, this concept tests your understanding of high availability within a datacenter, often appearing as a direct scenario where you must distinguish it from Availability Zones, which protect across datacenters. A common trap is confusing Availability Sets with Availability Zones; remember that sets are for intra-datacenter resilience, while zones are for inter-datacenter resilience. Memory tip: think of an Availability Set as a “safety net” inside one building, keeping your VMs on separate racks so a single power outage doesn’t take them all down.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company runs a critical application on Azure VMs. They need to ensure that if one VM fails, the application continues to serve users with another VM. The VMs should be placed in a configuration that protects against failures within a single datacenter. Which feature should they use?
Correct. An availability set protects against failures within a datacenter by distributing VMs across different fault and update domains.
B
Availability Zone
Why wrong: Incorrect. Availability zones protect against datacenter-level failures by placing VMs in physically separate locations within a region, not within a single datacenter.
C
Resource Group
Why wrong: Incorrect. A resource group is a logical container for resources, not a high-availability configuration for VMs.
D
Scale Set
Why wrong: Incorrect. A virtual machine scale set enables scaling VMs in and out, but does not by itself provide protection against single-datacenter failures; it often combines with availability zones or availability sets.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Availability Set
An Availability Set ensures that VMs are distributed across multiple fault domains (separate racks with independent power, cooling, and network) and update domains within a single Azure datacenter. This protects against hardware failures or maintenance events within that datacenter, so if one VM fails, another in a different fault domain continues serving users.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✓
Availability Set
Why this is correct
Correct. An availability set protects against failures within a datacenter by distributing VMs across different fault and update domains.
Related concept
Read the scenario before looking for a memorised answer.
✗
Availability Zone
Why it's wrong here
Incorrect. Availability zones protect against datacenter-level failures by placing VMs in physically separate locations within a region, not within a single datacenter.
✗
Resource Group
Why it's wrong here
Incorrect. A resource group is a logical container for resources, not a high-availability configuration for VMs.
✗
Scale Set
Why it's wrong here
Incorrect. A virtual machine scale set enables scaling VMs in and out, but does not by itself provide protection against single-datacenter failures; it often combines with availability zones or availability sets.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Availability Zones (which protect against datacenter-wide outages) with Availability Sets (which protect against failures within a single datacenter), leading them to choose Zones when the question explicitly specifies 'within a single datacenter'.
Detailed technical explanation
How to think about this question
An Availability Set groups VMs into up to 3 fault domains (each representing a physical rack with dedicated power and network) and up to 20 update domains (for planned maintenance). Under the hood, Azure ensures that VMs in the same Availability Set are placed on different hardware to avoid a single point of failure. In a real-world scenario, if a power supply fails in one rack, only VMs in that fault domain are affected, while others remain operational.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
TExam Day Tips
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
An e-commerce site experiences heavy traffic on Black Friday and near-zero traffic during off-peak weeks. Rather than provisioning permanent large VMs, the team uses auto-scaling groups that add capacity automatically under load and reduce it overnight. Questions like this test whether you understand elasticity, availability zones, and cloud compute scaling patterns.
Related glossary terms
Concepts from this question explained
These glossary pages explain the core terms tested in this AZ-900 question in full detail.
Describe Azure architecture and services — This question tests Describe Azure architecture and services — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Availability Set — An Availability Set ensures that VMs are distributed across multiple fault domains (separate racks with independent power, cooling, and network) and update domains within a single Azure datacenter. This protects against hardware failures or maintenance events within that datacenter, so if one VM fails, another in a different fault domain continues serving users.
What should I do if I get this AZ-900 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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