Question 550 of 1,031

Describe Azure architecture and services →mediumMultiple ChoiceObjective-mapped

Quick Answer

The answer is that placing both VMs in the same availability set distributes them across different fault domains and update domains within the datacenter. This is correct because fault domains isolate VMs onto separate physical racks with independent power, cooling, and networking, so a single hardware failure cannot take down both servers. Simultaneously, update domains group VMs into batches that are rebooted sequentially during planned Azure maintenance, ensuring that only one domain is updated at a time. On the AZ-900 exam, this concept tests your understanding of high availability at the infrastructure layer, often appearing as a scenario where you must choose between availability sets, zones, or scale sets. A common trap is assuming that placing VMs in the same set guarantees they run on the same hardware, when the opposite is true. Remember the mnemonic “Fault for Failure, Update for Upkeep” to recall that fault domains protect against hardware crashes while update domains protect against planned patching.

AZ-900 Describe Azure architecture and services Practice Question

This AZ-900 practice question tests your understanding of describe azure architecture and services. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 deploys two Azure virtual machines (VMs) into the same availability set. The first VM runs a web server and the second runs a database server. The company's primary concern is that during Azure platform maintenance events (e.g., OS updates to the underlying host) or in the event of a hardware failure in the datacenter, both VMs should not be impacted at the same time. Which benefit does placing the VMs in the same availability set provide?

Clue words in this question

Noticing these words before you look at the options changes how you read each choice.

Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Clue: "primary"
Why it matters: Asks for the main purpose or function, not a secondary benefit. Eliminate answers that describe side-effects or partial functions.

Question 1mediummultiple choice

Full question →

A
Both VMs will be placed on the same physical server for performance consistency.
Why wrong: Incorrect. An availability set intentionally separates VMs across multiple physical servers (fault domains) to avoid a single point of failure. Placing them on the same server would create a single point of failure, which is the opposite of the intended benefit.
B
The VMs will be distributed across different fault domains and update domains within the datacenter.
Correct. When VMs are added to an availability set, Azure automatically distributes them across up to three fault domains and multiple update domains. This distribution ensures that a hardware failure or planned maintenance event affects only one fault domain or update domain at a time, keeping the other VM running.
C
The VMs will be automatically load-balanced and scaled based on CPU usage.
Why wrong: Incorrect. An availability set does not provide load balancing or auto-scaling. Load balancing requires a separate Azure Load Balancer or Application Gateway. Auto-scaling requires a Virtual Machine Scale Set. The sole purpose of an availability set is to improve availability by separating VMs within a datacenter.
D
The VMs will be replicated to a second Azure region for disaster recovery.
Why wrong: Incorrect. An availability set operates only within a single Azure region and datacenter. For cross-region disaster recovery, you would need Azure Site Recovery or paired regions. Availability sets provide intra-datacenter resilience, not geo-redundancy.

Full breakdown with real-world context →

Answer choices

Why each option matters

Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.

Correct answer & explanation

✓

The VMs will be distributed across different fault domains and update domains within the datacenter.

An availability set ensures that VMs are distributed across different fault domains (separate power, cooling, and network racks) and update domains (groups that are updated sequentially during planned maintenance). This isolation guarantees that a hardware failure or a platform maintenance event will not affect both VMs simultaneously, meeting the company's primary concern.

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.

✗
Both VMs will be placed on the same physical server for performance consistency.
Why it's wrong here
Incorrect. An availability set intentionally separates VMs across multiple physical servers (fault domains) to avoid a single point of failure. Placing them on the same server would create a single point of failure, which is the opposite of the intended benefit.
✓
The VMs will be distributed across different fault domains and update domains within the datacenter.
Why this is correct
Correct. When VMs are added to an availability set, Azure automatically distributes them across up to three fault domains and multiple update domains. This distribution ensures that a hardware failure or planned maintenance event affects only one fault domain or update domain at a time, keeping the other VM running.
Clue confirmation
The clue words "first", "primary" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
The VMs will be automatically load-balanced and scaled based on CPU usage.
Why it's wrong here
Incorrect. An availability set does not provide load balancing or auto-scaling. Load balancing requires a separate Azure Load Balancer or Application Gateway. Auto-scaling requires a Virtual Machine Scale Set. The sole purpose of an availability set is to improve availability by separating VMs within a datacenter.
✗
The VMs will be replicated to a second Azure region for disaster recovery.
Why it's wrong here
Incorrect. An availability set operates only within a single Azure region and datacenter. For cross-region disaster recovery, you would need Azure Site Recovery or paired regions. Availability sets provide intra-datacenter resilience, not geo-redundancy.

Common exam traps

Common exam trap: answer the scenario, not the keyword

The trap here is that candidates often confuse availability sets with availability zones or assume that placing VMs in the same set means they are co-located for performance, when in fact the set is designed to spread them apart for resilience.

Detailed technical explanation

How to think about this question

An availability set logically groups VMs into up to 3 fault domains and up to 20 update domains. Fault domains represent physical isolation (separate racks with independent power and networking), while update domains ensure that during a platform update, only one update domain is rebooted at a time. This design aligns with the Azure SLA of 99.95% for two or more VMs in an availability set, as opposed to 99.9% for a single VM.

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.

What to study next

Got this wrong? Here's your next step.

Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.

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FAQ

Questions learners often ask

What does this AZ-900 question test?

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: The VMs will be distributed across different fault domains and update domains within the datacenter. — An availability set ensures that VMs are distributed across different fault domains (separate power, cooling, and network racks) and update domains (groups that are updated sequentially during planned maintenance). This isolation guarantees that a hardware failure or a platform maintenance event will not affect both VMs simultaneously, meeting the company's primary concern.

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.

Are there clue words in this question I should notice?

Yes — watch for: "first", "primary". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.

What is the key concept behind this question?

Read the scenario before looking for a memorised answer.

About these practice questions

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Same concept, more angles

1 more ways this is tested on AZ-900

These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.

Variation 1. What is the purpose of Azure Availability Sets?

easy

A.To deploy VMs across multiple Azure regions for global availability
✓ B.To protect VMs from hardware failures and planned maintenance within a single datacenter
C.To automatically scale the number of VMs based on CPU utilization
D.To provide dedicated physical servers for a single organization

Why B: Azure Availability Sets protect VMs from hardware failures and planned maintenance within a single datacenter by grouping VMs into fault domains (to isolate against rack-level failures) and update domains (to sequence planned maintenance reboots). This ensures at least one VM instance remains available during Azure infrastructure updates or unexpected hardware issues.

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