Protect VMs During Planned Maintenance
Two application VMs are in the same Azure region. They must stay available during planned host maintenance, but the business does not require protection from a full datacenter outage. Which placement option should you use?
Quick Answer
The answer is an availability set, because it provides planned maintenance protection for VMs in the same region without covering full datacenter outages. An availability set logically groups VMs across multiple update domains—up to 20—so that during Azure host maintenance, only one update domain is rebooted at a time, keeping your application VMs available. This directly meets the requirement to stay online during planned updates while avoiding the cost and complexity of an availability zone, which would protect against a full datacenter failure. On the AZ-104 exam, this question tests your ability to distinguish between high-availability options: availability sets for intra-datacenter resilience versus availability zones for cross-datacenter protection. A common trap is choosing zones when only planned maintenance is needed, but remember that zones add redundancy across separate physical locations. Memory tip: think of an availability set as a “neighborhood” within one datacenter—if one house (update domain) is under maintenance, the rest stay powered on.
⚠ Common exam trap
A common mix-up: candidates choose Availability zones because they see 'high availability' and assume it's always the best option, missing the explicit constraint that only planned host maintenance needs to be covered, not 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
✓
Availability set
An availability set distributes VMs across multiple fault domains (up to 3) and update domains (up to 20) within a single Azure datacenter. This ensures that during planned host maintenance, only one update domain is taken offline at a time, keeping the application VMs available. Since the requirement does not include protection from a full datacenter outage, an availability set is the correct and cost-effective placement 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 set
Why this is correct
An availability set spreads VMs across fault and update domains so planned maintenance affects only part of the group at a time.
- ✗
Availability zone
Why it's wrong here
A zone can improve resilience, but it is more than required when only host maintenance protection is needed.
When this WOULD be correct
If the question required protection from a full datacenter outage (e.g., 'must survive a datacenter failure') or demanded 99.99% uptime SLA, availability zones would be correct. For example: 'Two VMs must remain available during a regional disaster; which placement option?'
- ✗
Shared disk
Why it's wrong here
A shared disk supports clustering scenarios, but it does not place VMs to reduce maintenance impact.
When this WOULD be correct
When the question asks for a solution to enable two VMs to share a single block storage volume for a failover cluster application (e.g., SQL Server FCI) in the same availability set or zone.
- ✗
Snapshot set
Why it's wrong here
Snapshots help capture disk state for recovery, but they do not distribute running VMs across maintenance boundaries.
When this WOULD be correct
If the question asked for a method to create point-in-time backups of managed disks for a VM, or to replicate disks across regions for disaster recovery, then 'Snapshot set' (or snapshot) 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.
✓Availability setCorrect answer▾
Why this is correct
An availability set spreads VMs across fault and update domains so planned maintenance affects only part of the group at a time.
✗Availability zoneWrong answer — click to see why▾
Why this is wrong here
Availability zones protect against datacenter-level failures, but the question explicitly states no protection from a full datacenter outage is required. Zones also incur cross-zone latency and cost, which are unnecessary for planned host maintenance.
★ When this WOULD be the correct answer
If the question required protection from a full datacenter outage (e.g., 'must survive a datacenter failure') or demanded 99.99% uptime SLA, availability zones would be correct. For example: 'Two VMs must remain available during a regional disaster; which placement option?'
Why candidates choose this
Candidates confuse 'availability' with 'high availability' and assume zones always provide better uptime, overlooking the specific requirement for planned maintenance only, not disaster recovery.
✗Shared diskWrong answer — click to see why▾
Why this is wrong here
Shared disks allow multiple VMs to access the same managed disk simultaneously for clustered applications, but they do not provide high availability against planned host maintenance or datacenter outages.
★ When this WOULD be the correct answer
When the question asks for a solution to enable two VMs to share a single block storage volume for a failover cluster application (e.g., SQL Server FCI) in the same availability set or zone.
Why candidates choose this
Candidates may confuse shared disks with high availability features, thinking that sharing storage inherently provides redundancy against maintenance events.
✗Snapshot setWrong answer — click to see why▾
Why this is wrong here
Snapshot set is not a valid Azure placement option; it refers to a collection of disk snapshots used for backup or disaster recovery, not for VM placement during planned maintenance.
★ When this WOULD be the correct answer
If the question asked for a method to create point-in-time backups of managed disks for a VM, or to replicate disks across regions for disaster recovery, then 'Snapshot set' (or snapshot) would be correct.
Why candidates choose this
Candidates may confuse 'snapshot set' with availability sets due to the word 'set', or incorrectly think snapshots can provide high availability during maintenance.
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
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
Azure datacenter
An Azure datacenter is a physical facility that houses Microsoft's cloud computing infrastructure, including servers, storage, and networking equipment, to deliver Azure services globally.
About these practice questions
One of 1,049 original AZ-104 practice questions on Courseiva, each with a full explanation and wrong-answer analysis — not 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-104
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. Two application VMs run in the same Azure region. The business wants to reduce the chance that both VMs are rebooted during planned host maintenance, but a datacenter outage is not part of the requirement. What should the administrator configure?
easy- ✓ A.Availability set
- B.Availability zone
- C.Azure Load Balancer
- D.Virtual machine scale set
Why A: An availability set ensures that VMs are placed on different fault domains and update domains within the same Azure datacenter. This configuration guarantees that during planned host maintenance, only one update domain is rebooted at a time, reducing the chance that both VMs are rebooted simultaneously. Since the requirement explicitly excludes a datacenter outage, an availability set is the correct choice to protect against planned maintenance events.
Variation 2. A company has two application VMs in the same Azure region. The main requirement is to reduce downtime during planned host maintenance. The business does not require protection from a complete datacenter outage. Which option should you choose?
easy- A.Availability zones
- ✓ B.Availability set
- C.Virtual machine scale set
- D.Proximity placement group
Why B: An availability set distributes VMs across multiple fault domains and update domains within a single Azure datacenter. During planned host maintenance, Azure updates one update domain at a time, ensuring that only a subset of VMs are rebooted simultaneously, thereby reducing downtime. This meets the requirement of protecting against planned maintenance without needing cross-datacenter redundancy.
JA
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.