- A
Use an ephemeral OS disk.
An ephemeral OS disk is the cheapest OS storage choice for a VM that can be recreated from image often. It is acceptable here because the scenario explicitly says the OS can be lost on reimage.
- B
Place build caches and artifacts on a separate managed data disk.
A separate managed data disk provides persistence for build caches and artifacts across nightly rebuilds. That keeps the stateful pieces safe even though the OS disk itself is disposable.
- C
Use a Premium SSD OS disk so the reimage is preserved.
Why wrong: A premium OS disk is not what preserves the VM during reimage, and it is more expensive than necessary. The scenario specifically allows the OS disk to be lost.
- D
Store the caches only on the temporary resource disk.
Why wrong: Temporary resource disks are not durable and are cleared during host changes or deallocation events. They are unsuitable for data that must persist across rebuilds.
- E
Use an availability set to make the OS disk persistent.
Why wrong: Availability sets improve placement resilience, but they do not turn the OS disk into durable persistent storage. Persistence is provided by the disk type, not by the availability feature.
Quick Answer
The answer is to use an ephemeral OS disk combined with a separate managed data disk. This works because the ephemeral OS disk uses local VM storage that is destroyed on deallocation or reimage, satisfying the requirement that the OS can be lost, while the separate managed data disk persists independently of the OS lifecycle and can be reattached to the new VM instance. On the AZ-104 exam, this scenario tests your understanding of Azure disk types and their lifecycle behaviors, often appearing as a two-part selection where candidates mistakenly choose a standard OS disk or forget to pair the ephemeral disk with a data disk. A common trap is assuming a managed OS disk alone will persist caches, but reimaging still wipes it. Remember the mnemonic: "Ephemeral for the OS, persistent for the payload" to keep the two roles straight.
AZ-104 Deploy and Manage Azure Compute Practice Question
This AZ-104 practice question tests your understanding of deploy and manage azure compute. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A build agent VM is recreated from image every night. The OS can be lost on reimage, but build caches and artifacts must persist across rebuilds. The team also wants the cheapest OS storage option that supports this pattern. Which two choices should you make? Select two.
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
Use an ephemeral OS disk.
Option A is correct because an ephemeral OS disk uses the local VM storage or temp SSD, which is destroyed when the VM is deallocated or reimaged. This matches the requirement that the OS can be lost on reimage. Option B is correct because placing build caches and artifacts on a separate managed data disk ensures they persist independently of the OS disk lifecycle; data disks are not affected by OS reimaging and can be reattached to the new VM instance.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding 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.
- ✓
Use an ephemeral OS disk.
Why this is correct
An ephemeral OS disk is the cheapest OS storage choice for a VM that can be recreated from image often. It is acceptable here because the scenario explicitly says the OS can be lost on reimage.
Related concept
Read the scenario before looking for a memorised answer.
- ✓
Place build caches and artifacts on a separate managed data disk.
Why this is correct
A separate managed data disk provides persistence for build caches and artifacts across nightly rebuilds. That keeps the stateful pieces safe even though the OS disk itself is disposable.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
Use a Premium SSD OS disk so the reimage is preserved.
Why it's wrong here
A premium OS disk is not what preserves the VM during reimage, and it is more expensive than necessary. The scenario specifically allows the OS disk to be lost.
- ✗
Store the caches only on the temporary resource disk.
Why it's wrong here
Temporary resource disks are not durable and are cleared during host changes or deallocation events. They are unsuitable for data that must persist across rebuilds.
- ✗
Use an availability set to make the OS disk persistent.
Why it's wrong here
Availability sets improve placement resilience, but they do not turn the OS disk into durable persistent storage. Persistence is provided by the disk type, not by the availability feature.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the temporary resource disk (which is also ephemeral) with a managed data disk, or assume that Premium SSD or availability sets provide persistence, when in fact only a separate managed data disk ensures data survives OS reimaging.
Trap categories for this question
Scenario analysis trap
A premium OS disk is not what preserves the VM during reimage, and it is more expensive than necessary. The scenario specifically allows the OS disk to be lost.
Detailed technical explanation
How to think about this question
Ephemeral OS disks are backed by the VM's local temporary storage (SSD or NVMe) and are not replicated to Azure Storage, making them cost-free for the OS disk itself (only compute and managed data disks incur charges). When a VM is reimaged, the ephemeral OS disk is reset to the original image, while any attached managed data disks remain intact and can be reattached to the rebuilt VM. This pattern is common for stateless build agents where the OS is disposable but build outputs must survive.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A startup's cloud architect reviews their monthly bill and notices costs are higher than expected for a long-running batch job. Switching from on-demand instances to Reserved Instances — or using Spot/Preemptible VMs — can reduce compute costs by up to 72 %. Questions like this test whether you understand the tradeoffs between commitment, flexibility, and cost across cloud pricing models.
What to study next
Got this wrong? Here's your next step.
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FAQ
Questions learners often ask
What does this AZ-104 question test?
Deploy and Manage Azure Compute — This question tests Deploy and Manage Azure Compute — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Use an ephemeral OS disk. — Option A is correct because an ephemeral OS disk uses the local VM storage or temp SSD, which is destroyed when the VM is deallocated or reimaged. This matches the requirement that the OS can be lost on reimage. Option B is correct because placing build caches and artifacts on a separate managed data disk ensures they persist independently of the OS disk lifecycle; data disks are not affected by OS reimaging and can be reattached to the new VM instance.
What should I do if I get this AZ-104 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Last reviewed: Jun 11, 2026
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.
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