AZ-305 Design infrastructure solutions Practice Question
A company has virtual machines in Azure that need to be grouped across multiple fault domains and update domains to ensure high availability. They plan to deploy three VMs running the same application tier. Which Azure feature should they use to provide redundancy within a single region?
⚠ Common exam trap
Many candidates confuse Availability Zones (which provide datacenter-level isolation) with Availability Sets (which provide rack-level isolation within a single datacenter), leading them to select Availability Zones when the scenario only requires intra-datacenter redundancy.
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 (shared hardware, power, and networking) and update domains (planned maintenance) within a single Azure datacenter. This ensures that at least one VM remains available during both hardware failures and Azure patching cycles. For three VMs running the same application tier, an Availability Set provides the required redundancy without the complexity of zone-level isolation.
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 Zone
Why it's wrong here
Availability Zones are physically separate datacenters within an Azure region, each with independent power, cooling, and networking. Deploying VMs across zones protects against a complete datacenter failure and provides a higher 99.99% SLA, but it does not serve the requirement of grouping VMs within a single datacenter across fault and update domains. Using zones would also introduce cross-zone network latency and is more expensive than an Availability Set, making it the wrong choice for this scenario.
- ✓
Availability Set
Why this is correct
An Availability Set is the correct grouping construct because it logically groups VMs so that Azure automatically distributes them across fault domains (distinct hardware racks with shared power and network switches) and update domains (groups that undergo planned maintenance one at a time). This placement ensures that during either hardware failure or Azure patching, at least one VM in the set remains available, meeting the high-availability requirement within a single datacenter. Availability Sets do not require identical VM configurations, allowing heterogeneous workloads to be protected together.
- ✗
Virtual Machine Scale Set with manual scaling
Why it's wrong here
A Virtual Machine Scale Set is designed for running a large number of identical VMs that can be automatically scaled in or out based on demand, not for general-purpose grouping of heterogeneous VMs for high availability. Even when scaling is set to manual, the scale set still treats instances as a uniform pool and does not provide the same fault-domain and update-domain placement guarantees as an Availability Set unless it is explicitly configured with availability zones or an availability set. For this question, the requirement is simply grouping VMs for HA, not elastic scaling, so a scale set with manual scaling is an inappropriate and overcomplicated choice.
- ✗
Azure Site Recovery
Why it's wrong here
Azure Site Recovery is a disaster recovery service that replicates Azure VMs or on-premises machines to a secondary Azure region, enabling failover in the event of a catastrophic regional outage. It is entirely focused on recovery after a disaster, not on the initial high-availability placement of VMs within a single region or datacenter. Site Recovery introduces replication overhead and recovery time objectives, whereas the requirement here is for continuous availability during local hardware or maintenance events, which is exactly what an Availability Set provides.
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JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This AZ-305 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-305 exam.