AZ-900 Describe Azure architecture and services Practice Question
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?
⚠ Common exam trap
It's easy for candidates to 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.
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.
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.
When this WOULD be correct
This option would be correct if the question asked about a single VM or multiple VMs that need to be placed on the same physical server for low-latency communication or to meet licensing requirements, such as in a tightly coupled application where performance consistency is critical.
- ✓
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.
- ✗
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.
When this WOULD be correct
If the question asked about ensuring high availability and distributing traffic across multiple VMs while automatically adjusting capacity based on demand, then using an Azure Load Balancer with a Virtual Machine Scale Set would be correct.
- ✗
The VMs will be replicated to a second Azure region for disaster recovery.
Why it's wrong here
An availability set operates entirely within a single Azure datacenter and region; it provides no mechanism for replicating VMs or their data to another geographic location. Cross-region disaster recovery requires separate services such as Azure Site Recovery to replicate virtual machines to a secondary region, or Azure paired regions for storage replication. Therefore, while the availability set improves intra-datacenter resilience, it has no effect on disaster recovery beyond the local datacenter boundary.
When this WOULD be correct
This option would be correct if the question asked about a solution to protect against a regional outage, such as using Azure Site Recovery or geo-redundant storage to replicate VMs to a secondary region.
Option-by-option analysis
Why each answer is right or wrong
Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The AZ-900 exam frequently reuses these exact scenarios with slightly different constraints.
✓The VMs will be distributed across different fault domains and update domains within the datacenter.Correct answer▾
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.
✗Both VMs will be placed on the same physical server for performance consistency.Wrong answer — click to see why▾
Why this is wrong here
Placing VMs in the same availability set does not place them on the same physical server; instead, it distributes them across different fault and update domains to avoid simultaneous impact from hardware failures or maintenance.
★ When this WOULD be the correct answer
This option would be correct if the question asked about a single VM or multiple VMs that need to be placed on the same physical server for low-latency communication or to meet licensing requirements, such as in a tightly coupled application where performance consistency is critical.
Why candidates choose this
Candidates may mistakenly think that availability sets group VMs together physically for performance benefits, confusing the concept of availability with performance optimization.
✗The VMs will be automatically load-balanced and scaled based on CPU usage.Wrong answer — click to see why▾
Why this is wrong here
Placing VMs in an availability set does not automatically configure load balancing or scaling; those require separate Azure services like Load Balancer and Scale Sets.
★ When this WOULD be the correct answer
If the question asked about ensuring high availability and distributing traffic across multiple VMs while automatically adjusting capacity based on demand, then using an Azure Load Balancer with a Virtual Machine Scale Set would be correct.
Why candidates choose this
Candidates may confuse availability sets with load balancing and scaling features, assuming that grouping VMs together inherently provides these capabilities.
✗The VMs will be replicated to a second Azure region for disaster recovery.Wrong answer — click to see why▾
Why this is wrong here
Placing VMs in an availability set does not provide disaster recovery across regions; it only protects against failures within a single datacenter by distributing VMs across fault and update domains.
★ When this WOULD be the correct answer
This option would be correct if the question asked about a solution to protect against a regional outage, such as using Azure Site Recovery or geo-redundant storage to replicate VMs to a secondary region.
Why candidates choose this
Candidates may confuse high availability within a datacenter with disaster recovery across regions, or think that 'replication' is a general feature of availability sets.
Analysis generated from the official AZ-900blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”
Go deeper
Related to this question
Learn chapter
Azure Regions and Geographies
Key term
Availability set
An Availability set is a cloud computing feature that groups virtual machines across multiple fault domains and update domains to ensure high availability during hardware failures or planned maintenance.
Key term
Availability
Availability is the measure of how often a system or service is operational and accessible when needed, typically expressed as a percentage of uptime.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-900 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the AZ-900 exam.