AZ-104 Deploy and Manage Azure Compute Practice Question
Exhibit
Workload notes: - Region: East US - Two application VMs will run in the same region - Requirement: survive planned host maintenance and a host failure - Requirement: no need for datacenter-level resilience
Based on the exhibit, the business wants two Azure VMs to stay available if a host is patched or fails. A full datacenter outage is not part of the requirement. What should you use?
⚠ Common exam trap
Watch out — candidates often confuse availability zones (which protect against datacenter-level failures) with availability sets (which protect against host-level failures), 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
✓
Deploy the VMs in an availability set.
An availability set protects against failures within a single datacenter by distributing VMs across multiple fault domains (physical racks with separate power and network) and update domains (groups that are patched sequentially). This ensures that during host patching or a host failure, at least one VM remains available, meeting the requirement without needing to survive a full datacenter outage.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Deploy the VMs in an availability set.
Why this is correct
An availability set is designed to protect VMs from host-level issues such as planned maintenance and individual hardware failures. It spreads VMs across update and fault domains, which fits the requirement exactly when datacenter-level protection is not needed.
- ✗
Deploy the VMs in the same availability zone.
Why it's wrong here
Placing both VMs in the same availability zone ties them to the same independently powered and cooled datacenter facility within the region. A zone-level outage—such as a datacenter-wide power failure—would take both VMs offline, so this configuration still does not address host-level failures; moreover, VMs within a single zone can reside on the same physical host, making them vulnerable to the exact host maintenance and hardware issues the business wants to avoid. The requirement is about surviving planned maintenance and a specific hardware failure, not an entire datacenter failure, so using an availability zone is both overkill and insufficient. Proper zone-based high availability would require placing the VMs in separate zones.
When this WOULD be correct
If the business requirement were to protect against a full datacenter outage (e.g., due to a natural disaster or power failure), deploying VMs in different availability zones would be correct. For example, a question stating 'The VMs must remain available if an entire datacenter fails' would make B the answer.
- ✗
Use a virtual machine scale set with autoscale only.
Why it's wrong here
A virtual machine scale set with autoscale rules only adjusts the instance count based on metrics like CPU or memory usage; it does not inherently guarantee placement across fault domains or update domains unless you explicitly configure an availability zone or use multiple placement groups. Autoscaling is designed to handle load changes, not to provide host-level fault tolerance, and with only two instances, an underlying host failure could still affect both instances if they happen to share the same physical host. While scale sets can be part of a high-availability architecture, simply enabling autoscale fails to meet the specific requirement of keeping two VMs running through host maintenance and hardware failures.
When this WOULD be correct
When the requirement is to automatically adjust the number of VM instances based on CPU or memory metrics to handle variable load, and availability during host maintenance is not a primary concern. For example, a web app that needs to scale out during peak hours and scale in during off-peak.
- ✗
Place both VMs on a dedicated host.
Why it's wrong here
A dedicated host is a single physical server allocated exclusively to you, and all VMs placed on it share that same underlying hardware. If the host experiences a hardware failure or requires planned maintenance, every VM on that host fails or restarts simultaneously, creating a single point of failure. An availability set, by contrast, spreads VMs across different hosts in multiple fault domains and update domains, which directly protects against host-level outages. Therefore, a dedicated host does not meet the requirement for the two VMs to stay available during host-level events.
When this WOULD be correct
If the requirement included compliance or licensing needs that mandate physical isolation from other customers, and the business accepted the risk of a single host failure, then deploying VMs on a dedicated host would be correct.
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.
✓Deploy the VMs in an availability set.Correct answer▾
Why this is correct
An availability set is designed to protect VMs from host-level issues such as planned maintenance and individual hardware failures. It spreads VMs across update and fault domains, which fits the requirement exactly when datacenter-level protection is not needed.
✗Deploy the VMs in the same availability zone.Wrong answer — click to see why▾
Why this is wrong here
Availability zones protect against datacenter-level failures, not host-level failures. The requirement is only for host patching or failure, so an availability set (which protects against host failures within a single datacenter) is sufficient and more cost-effective.
★ When this WOULD be the correct answer
If the business requirement were to protect against a full datacenter outage (e.g., due to a natural disaster or power failure), deploying VMs in different availability zones would be correct. For example, a question stating 'The VMs must remain available if an entire datacenter fails' would make B the answer.
Why candidates choose this
Candidates may confuse availability zones with availability sets, thinking that zones provide higher availability for all scenarios, or they may over-engineer the solution by choosing a more expensive option that addresses a broader failure scope than required.
✗Use a virtual machine scale set with autoscale only.Wrong answer — click to see why▾
Why this is wrong here
A virtual machine scale set with autoscale only does not guarantee availability during host patching or failure; it scales out based on load, not to maintain a fixed number of VMs across fault domains. The requirement is for two VMs to stay available, not to scale dynamically.
★ When this WOULD be the correct answer
When the requirement is to automatically adjust the number of VM instances based on CPU or memory metrics to handle variable load, and availability during host maintenance is not a primary concern. For example, a web app that needs to scale out during peak hours and scale in during off-peak.
Why candidates choose this
Candidates may think that a scale set inherently provides high availability because it can create multiple instances, but they overlook that autoscale alone does not distribute VMs across fault domains to protect against host failures.
✗Place both VMs on a dedicated host.Wrong answer — click to see why▾
Why this is wrong here
Dedicated hosts isolate VMs from other tenants but do not protect against host patching or failure within the same host; a single dedicated host is a single point of failure, so both VMs would still be affected by a host issue.
★ When this WOULD be the correct answer
If the requirement included compliance or licensing needs that mandate physical isolation from other customers, and the business accepted the risk of a single host failure, then deploying VMs on a dedicated host would be correct.
Why candidates choose this
Candidates may think dedicated hosts provide high availability by isolating VMs from other tenants, but they overlook that VMs on the same dedicated host share the same physical hardware and thus are not resilient to host-level failures.
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?”
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Dynamic Membership Groups
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.
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
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