- A
A Premium SSD managed OS disk
Why wrong: Premium SSD is durable, but it is not the fastest choice for a disposable OS disk.
- B
An ephemeral OS disk
Ephemeral OS disks use local storage and provide very fast boot with no persistence requirement.
- C
A Standard SSD managed OS disk
Why wrong: Standard SSD is durable, but it still stores the OS disk persistently and boots more slowly.
- D
The VM temporary disk as the operating system disk
Why wrong: The temporary disk is not intended to be used as the official persistent OS disk choice.
Question 314 of 1,170
Use Ephemeral OS Disks for Fastest Boot Times on Development VMs That Don't Need Persistence
This AZ-104 practice question tests your understanding of deploy and manage azure compute. Match the stated requirement to the specific cloud service, access model, or configuration option — many options are valid in isolation but not for this scenario. 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 development VM is recreated from scratch every week. The team wants the operating system disk to boot as quickly as possible and does not need the OS disk contents to survive deallocation. Which disk choice should the administrator make?
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 ephemeral OS disk
An ephemeral OS disk is created on the local VM host storage, not on Azure managed storage, which eliminates network latency and provides significantly faster boot times. Since the team does not need the OS disk contents to survive deallocation and recreates the VM weekly, ephemeral disks are ideal as they are reset to the original image state on each deployment.
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.
- ✗
A Premium SSD managed OS disk
Why it's wrong here
Premium SSD is durable, but it is not the fastest choice for a disposable OS disk.
When this WOULD be correct
When the VM requires persistent OS disk data across deallocations and needs high performance for I/O-intensive workloads, such as a production database server that must retain OS state after shutdown.
- ✓
An ephemeral OS disk
Why this is correct
Ephemeral OS disks use local storage and provide very fast boot with no persistence requirement.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
A Standard SSD managed OS disk
Why it's wrong here
Standard SSD is durable, but it still stores the OS disk persistently and boots more slowly.
When this WOULD be correct
When the VM requires persistent OS disk data across deallocations and reboots, and cost is a concern over performance, such as for a development VM that needs to retain state between sessions but does not require high IOPS.
- ✗
The VM temporary disk as the operating system disk
Why it's wrong here
The temporary disk is not intended to be used as the official persistent OS disk choice.
When this WOULD be correct
If the question asked for a disk to store page files or temporary application data that can be lost without impact, and cost savings are prioritized, using the temporary disk 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.
✓An ephemeral OS diskCorrect answer▾
Why this is correct
Ephemeral OS disks use local storage and provide very fast boot with no persistence requirement.
✗A Premium SSD managed OS diskWrong answer — click to see why▾
Why this is wrong here
Premium SSD managed disks persist data even after deallocation, which contradicts the requirement that OS disk contents do not survive deallocation. They also do not boot faster than ephemeral disks.
★ When this WOULD be the correct answer
When the VM requires persistent OS disk data across deallocations and needs high performance for I/O-intensive workloads, such as a production database server that must retain OS state after shutdown.
Why candidates choose this
Candidates often associate Premium SSD with 'fastest boot' and overlook the ephemeral disk option, not realizing that ephemeral disks are optimized for stateless, fast-boot scenarios.
✗A Standard SSD managed OS diskWrong answer — click to see why▾
Why this is wrong here
Standard SSD managed disks persist data even after deallocation, which contradicts the requirement that OS disk contents do not need to survive deallocation. Additionally, they are slower than ephemeral disks for boot performance.
★ When this WOULD be the correct answer
When the VM requires persistent OS disk data across deallocations and reboots, and cost is a concern over performance, such as for a development VM that needs to retain state between sessions but does not require high IOPS.
Why candidates choose this
Candidates may choose Standard SSD as a cost-effective compromise, not realizing that the question explicitly prioritizes boot speed and does not require persistence, making ephemeral disks the optimal choice.
✗The VM temporary disk as the operating system diskWrong answer — click to see why▾
Why this is wrong here
The VM temporary disk (D: drive on Windows, /dev/sdb on Linux) is not supported as an OS disk; it is intended for temporary data and is not bootable.
★ When this WOULD be the correct answer
If the question asked for a disk to store page files or temporary application data that can be lost without impact, and cost savings are prioritized, using the temporary disk would be correct.
Why candidates choose this
Candidates may confuse the temporary disk's fast, local storage with the ephemeral OS disk's purpose, thinking both provide similar speed and data loss tolerance.
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?”
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often choose Premium SSD for 'fastest boot' without realizing that ephemeral OS disks bypass network storage entirely, offering even lower latency for boot operations, and that the temporary disk cannot be used as an OS disk despite its local nature.
Detailed technical explanation
How to think about this question
Ephemeral OS disks leverage the local NVMe or SSD storage of the Azure host, achieving read/write speeds up to 10x faster than managed disks for boot operations. They are supported on specific VM series (e.g., Dsv3, Esv3) and require the VM size to have a cache size at least as large as the OS disk. A key subtlety is that ephemeral disks cannot be used with certain features like Azure Backup or encryption at rest, and the OS disk is automatically deleted when the VM is deallocated or stopped.
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 media company stores terabytes of video archives that are accessed once a year for audit purposes. Moving these objects to a cold storage tier (Azure Archive, S3 Glacier, or Google Nearline) costs a fraction of hot storage. Questions like this test whether you understand storage tiers, access frequency tradeoffs, and retrieval latency requirements.
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: An ephemeral OS disk — An ephemeral OS disk is created on the local VM host storage, not on Azure managed storage, which eliminates network latency and provides significantly faster boot times. Since the team does not need the OS disk contents to survive deallocation and recreates the VM weekly, ephemeral disks are ideal as they are reset to the original image state on each deployment.
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
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, 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. A development VM is rebuilt often and does not need its operating system disk contents to survive deallocation. The team wants the lowest practical disk latency for the OS. Which disk option should the administrator choose?
easy- A.Standard HDD managed disk
- ✓ B.Ephemeral OS disk
- C.Geo-redundant storage for the OS disk
- D.A data disk formatted as the boot disk
Why B: Ephemeral OS disks use the local VM storage (SSD) rather than Azure managed disks, providing the lowest latency for OS read/write operations. Since the VM is rebuilt often and disk persistence is not required, the ephemeral disk is ideal because its contents are lost when the VM is deallocated, eliminating the need for a separate managed disk.
Variation 2. A development environment uses temporary test VMs that can be rebuilt at any time. The administrator wants the operating system disk to provide the lowest practical latency and does not need the disk data to survive a deallocate operation. Which OS disk option should be selected?
medium- A.Standard HDD managed disk.
- B.Premium SSD managed disk.
- ✓ C.Ephemeral OS disk.
- D.Ultra Disk managed disk.
Why C: Ephemeral OS disks use the local VM storage (temporary disk) rather than remote managed storage, which provides the lowest possible latency because data is stored directly on the host node. Since the test VMs can be rebuilt at any time and the disk data does not need to survive a deallocate operation, the ephemeral disk is ideal—it is automatically deleted when the VM is deallocated or deleted, and it avoids the cost and performance overhead of managed disks.
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Last reviewed: Jun 11, 2026
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