- A
Availability Zones
Why wrong: Availability Zones provide redundancy across physically separate datacenters within a region. This would satisfy the maintenance and rack failure requirements, but it may introduce additional costs due to inter-zone data transfer fees, and the requirement states that the solution must not incur additional costs beyond the VMs themselves. Therefore, Availability Zones are not the best choice.
- B
Availability Set
An Availability Set groups VMs across multiple fault domains (separate server racks) and update domains (for planned maintenance). This ensures that at least one VM remains available during maintenance and that a single rack failure does not affect both VMs. No additional cost is incurred for using an Availability Set.
- C
Azure Site Recovery
Why wrong: Azure Site Recovery (ASR) is a disaster recovery service used to replicate workloads to a secondary region for recovery during a regional outage. It is not designed for within-region high availability during maintenance or rack-level hardware failures, and it adds significant cost for replication and failover.
- D
Azure Load Balancer
Why wrong: An Azure Load Balancer distributes incoming traffic across multiple VMs. While it can work with an Availability Set to provide high availability, by itself it does not protect against rack failures or platform maintenance events. It also does not guarantee that VMs are placed on separate fault or update domains.
Quick Answer
The answer is the Availability Set. This feature distributes your two VMs across separate fault domains—essentially different server racks with independent power and networking—and separate update domains, which ensures that during Azure platform-initiated maintenance only one domain is rebooted at a time, leaving at least one VM running. A hardware failure in one rack will not affect the other VM because it resides in a different fault domain, and since Availability Sets incur no extra cost beyond the VMs themselves, they perfectly satisfy all three requirements. On the AZ-900 exam, this scenario tests your understanding of the fundamental difference between an Availability Set and an Availability Zone: the former protects against rack-level failures within a single datacenter, while the latter protects against entire datacenter outages across physically separate locations. A common trap is choosing Availability Zones because they sound more robust, but they would require additional cost for cross-zone traffic and do not meet the “no additional cost” requirement. Remember the mnemonic: “Set for the rack, Zone for the back”—an Availability Set handles failures in the server rack, while a Zone handles failures in the datacenter’s back end.
AZ-900 Describe Azure architecture and services Practice Question
This AZ-900 practice question tests your understanding of describe azure architecture and services. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. 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 plans to deploy two Azure virtual machines that host a critical web application. Both VMs will be in the same Azure region and the same virtual network. The company’s requirements are: 1) During Azure platform-initiated maintenance (e.g., OS updates), at least one VM must remain running. 2) If a hardware failure occurs in the server rack that hosts one VM, the other VM must not be affected. 3) The solution must not incur additional costs beyond the VMs themselves. Which Azure feature should the company configure?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"least"Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
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
Availability Set
An Availability Set distributes VMs across multiple fault domains (different server racks with independent power and networking) and update domains (groups that undergo platform maintenance sequentially). This ensures that during Azure-initiated maintenance, only one update domain is rebooted at a time, leaving at least one VM running, and that a hardware failure in one fault domain does not affect VMs in other fault domains. Availability Sets are free of charge beyond the cost of the VMs themselves, meeting all requirements.
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 Zones
Why it's wrong here
Availability Zones provide redundancy across physically separate datacenters within a region. This would satisfy the maintenance and rack failure requirements, but it may introduce additional costs due to inter-zone data transfer fees, and the requirement states that the solution must not incur additional costs beyond the VMs themselves. Therefore, Availability Zones are not the best choice.
- ✓
Availability Set
Why this is correct
An Availability Set groups VMs across multiple fault domains (separate server racks) and update domains (for planned maintenance). This ensures that at least one VM remains available during maintenance and that a single rack failure does not affect both VMs. No additional cost is incurred for using an Availability Set.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Azure Site Recovery
Why it's wrong here
Azure Site Recovery (ASR) is a disaster recovery service used to replicate workloads to a secondary region for recovery during a regional outage. It is not designed for within-region high availability during maintenance or rack-level hardware failures, and it adds significant cost for replication and failover.
- ✗
Azure Load Balancer
Why it's wrong here
An Azure Load Balancer distributes incoming traffic across multiple VMs. While it can work with an Availability Set to provide high availability, by itself it does not protect against rack failures or platform maintenance events. It also does not guarantee that VMs are placed on separate fault or update domains.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse Availability Zones (which provide physical separation across data centers) with Availability Sets (which provide fault and update domain isolation within a single data center), leading them to choose Availability Zones despite the cost and networking constraints that make Availability Sets the correct answer for this scenario.
Detailed technical explanation
How to think about this question
An Availability Set groups VMs into up to 3 fault domains (each representing a separate server rack with dedicated power and network switches) and up to 20 update domains (logical groups that determine the order of platform updates). During planned maintenance, Azure reboots VMs one update domain at a time, ensuring that at most one update domain is unavailable at any moment. This design guarantees a 99.95% SLA for multi-VM deployments when using an Availability Set, as opposed to the 99.9% SLA for individual VMs.
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
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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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: Availability Set — An Availability Set distributes VMs across multiple fault domains (different server racks with independent power and networking) and update domains (groups that undergo platform maintenance sequentially). This ensures that during Azure-initiated maintenance, only one update domain is rebooted at a time, leaving at least one VM running, and that a hardware failure in one fault domain does not affect VMs in other fault domains. Availability Sets are free of charge beyond the cost of the VMs themselves, meeting all requirements.
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: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Same concept, more angles
2 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. A company deploys virtual machines in Azure. They want to ensure that the VMs are distributed across multiple fault domains and update domains within an Azure datacenter to protect against hardware failures and maintenance. Which Azure construct should they use?
medium- ✓ A.A) Availability Set
- B.B) Availability Zone
- C.C) Region Pair
- D.D) Resource Group
Why A: An Availability Set is the correct Azure construct because it logically groups VMs to protect against both hardware failures (via fault domains) and planned maintenance (via update domains) within a single Azure datacenter. Fault domains distribute VMs across separate racks with independent power, cooling, and network, while update domains ensure VMs in different groups are not rebooted simultaneously during Azure host updates. This directly matches the requirement to isolate VMs across multiple fault and update domains within a datacenter.
Variation 2. A company deploys three Azure virtual machines (VMs) that host a critical line-of-business application. All three VMs are located in the same Azure region. The company notices that during planned maintenance events triggered by the Azure platform, such as host OS updates, all three VMs are updated simultaneously, causing the application to become unavailable. The company requires that during such maintenance, at least two VMs remain running to preserve application uptime. Which Azure feature should the company implement to logically group the VMs and ensure they are updated in separate batches?
medium- A.Azure Availability Zone
- ✓ B.Azure Availability Set
- C.Azure Virtual Machine Scale Set
- D.Azure Site Recovery
Why B: An Azure Availability Set logically groups VMs to protect against platform updates and faults. By placing VMs into an availability set, Azure assigns them to different update domains (default 5) and fault domains (default 2). During planned maintenance, only one update domain is rebooted at a time, ensuring that at most one of the three VMs is updated simultaneously, thus keeping at least two VMs running.
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Last reviewed: Jun 11, 2026
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