AZ-104 Deploy and Manage Azure Compute Practice Question
Two backend VMs must remain available if an Azure host is patched or fails. A full datacenter outage is not part of the requirement, and the team wants the VMs to stay in the same region with predictable east-west latency. Which placement option should the administrator choose?
⚠ Common exam trap
Many candidates confuse availability zones (which protect against datacenter failures) with availability sets (which protect against host failures within a single datacenter), leading them to choose zones even when the requirement explicitly excludes a full datacenter outage.
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
✓
An availability set
An availability set distributes VMs across multiple fault domains (separate physical racks with independent power, cooling, and network) within a single Azure datacenter. This protects against host patching and hardware failures while keeping VMs in the same datacenter, ensuring predictable east-west latency. The requirement explicitly excludes a full datacenter outage, so availability zones (which span separate datacenters) are unnecessary.
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 in separate datacenters
Why it's wrong here
Availability zones place VMs in separate physical datacenters within a region, which protects against an entire datacenter failure, not just a single host failure. This level of isolation is overkill for the stated requirement and introduces higher latency between VMs and additional cross-zone data transfer costs, so it is more complex and expensive than the simple host-failure protection an availability set provides.
When this WOULD be correct
If the requirement were to protect against a full datacenter outage (e.g., due to fire or flooding) while still staying within the same region, availability zones would be correct. For example: 'Two backend VMs must remain available if an entire Azure datacenter fails, but must stay in the same region for low latency.'
- ✓
An availability set
Why this is correct
An availability set spreads the two backend VMs across multiple fault domains (distinct racks with separate power and network switches) and update domains (hosts rebooted one at a time during patching). By placing each VM in a different fault domain, Azure guarantees that at least one VM stays running when a single physical host fails or undergoes maintenance, so this directly meets the resilience requirement with minimal configuration.
- ✗
A proximity placement group
Why it's wrong here
A proximity placement group only controls the physical closeness of VMs to reduce network latency; it does not enforce any separation into fault domains or update domains. If both backend VMs are placed in the same proximity group, they can still land on the same host, which means a single host failure can take both VMs offline, so it fails the stated availability requirement.
When this WOULD be correct
An administrator needs to minimize east-west latency between VMs for a high-performance computing workload, and availability is not a primary concern—only low latency matters.
- ✗
A single VM scale set instance
Why it's wrong here
A single VM scale set instance is just one virtual machine—if the host running that lone instance fails, the backend server becomes entirely unavailable, and there is no second VM to absorb the traffic. The requirement explicitly states two backend VMs must remain available, so a single instance cannot satisfy the need for redundancy at the individual host level.
When this WOULD be correct
When the requirement is to automatically scale out multiple identical VMs based on load, and high availability is achieved by using multiple instances in the scale set across availability zones or an availability set. For example, 'Deploy a scalable web application that can handle variable traffic with at least two VMs.'
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-104 exam frequently reuses these exact scenarios with slightly different constraints.
✓An availability setCorrect answer▾
Why this is correct
An availability set spreads the two backend VMs across multiple fault domains (distinct racks with separate power and network switches) and update domains (hosts rebooted one at a time during patching). By placing each VM in a different fault domain, Azure guarantees that at least one VM stays running when a single physical host fails or undergoes maintenance, so this directly meets the resilience requirement with minimal configuration.
✗Availability zones in separate datacentersWrong answer — click to see why▾
Why this is wrong here
Availability zones place VMs in physically separate datacenters within a region, which protects against a single host failure but also introduces cross-zone latency. The requirement specifies predictable east-west latency and staying within the same region without needing full datacenter redundancy, making availability sets a better fit.
★ When this WOULD be the correct answer
If the requirement were to protect against a full datacenter outage (e.g., due to fire or flooding) while still staying within the same region, availability zones would be correct. For example: 'Two backend VMs must remain available if an entire Azure datacenter fails, but must stay in the same region for low latency.'
Why candidates choose this
Candidates may think availability zones are always the best for high availability, not realizing they introduce cross-zone latency and are overkill when only host-level redundancy is needed.
✗A proximity placement groupWrong answer — click to see why▾
Why this is wrong here
A proximity placement group reduces network latency between VMs but does not protect against host patching or failure; it can place VMs on the same host, increasing failure risk.
★ When this WOULD be the correct answer
An administrator needs to minimize east-west latency between VMs for a high-performance computing workload, and availability is not a primary concern—only low latency matters.
Why candidates choose this
Candidates may confuse low latency with high availability, assuming that grouping VMs closely together also provides redundancy.
✗A single VM scale set instanceWrong answer — click to see why▾
Why this is wrong here
A single VM scale set instance does not provide high availability; it is just one VM. The requirement for two backend VMs to remain available during host patching or failure necessitates redundancy, which a single instance cannot offer.
★ When this WOULD be the correct answer
When the requirement is to automatically scale out multiple identical VMs based on load, and high availability is achieved by using multiple instances in the scale set across availability zones or an availability set. For example, 'Deploy a scalable web application that can handle variable traffic with at least two VMs.'
Why candidates choose this
Candidates may think a VM scale set inherently provides high availability because it can manage multiple VMs, but a single instance scale set offers no redundancy, confusing scalability with availability.
Analysis generated from the official AZ-104blueprint 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
Managed Identities for Azure Resources
Key term
Region
A region is a distinct geographic location where a cloud provider operates multiple data centers that are connected by low-latency networks and provide cloud services.
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.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-104 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-104 exam.