AZ-104 Deploy and Manage Azure Compute Practice Question
Exhibit
Development environment notes: - The VM is recreated frequently from an image - The OS disk contents do not need to be preserved after the VM is deallocated - The team wants the lowest practical OS disk latency - Data durability is not the top priority for this VM
Based on the exhibit, which OS disk option best fits a development VM that is rebuilt often and does not need the disk contents to survive deallocation?
⚠ Common exam trap
Watch out — candidates often assume a Standard HDD managed disk is the cheapest option for a development VM, overlooking that ephemeral disks incur no storage cost and automatically reset the OS on each rebuild, which is more cost-effective and operationally simpler for the described use case.
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 and not stored in Azure Storage, so it provides lower latency and is automatically deleted when the VM is deallocated. This makes it ideal for development VMs that are rebuilt often and do not require disk persistence across deallocations.
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 Standard HDD managed OS disk.
Why it's wrong here
A Standard HDD managed OS disk uses magnetic spinning media, resulting in significantly higher I/O latency and lower IOPS than an ephemeral OS disk, which is stored on high-speed local SSD or NVMe on the VM host. While Standard HDD is cheap and durable, it directly contradicts the requirement for the lowest practical latency for the OS disk. An ephemeral OS disk sacrifices persistence to achieve the best performance, which is exactly what a rebuildable development virtual machine requires.
When this WOULD be correct
This option would be correct for a development VM that needs to retain its OS disk data across deallocations (e.g., to preserve installed tools or configurations) and has low cost as a priority, with no need for high performance.
- ✓
An ephemeral OS disk.
Why this is correct
An ephemeral OS disk is the best match because it provides very fast local storage for the operating system and does not need to preserve data after deallocation. This is ideal for rebuildable development VMs where performance matters more than retaining the OS disk contents.
- ✗
A premium managed data disk used as the OS disk.
Why it's wrong here
A premium managed data disk is a separate volume used for application data, not a valid boot disk for a VM. Although a premium managed disk can be used as an OS disk, the wording 'data disk' indicates it is not attached as the boot disk; and in this scenario, the requirement explicitly asks for the lowest practical latency for a rebuildable development VM. An ephemeral OS disk on local VM storage provides lower latency than any attached managed disk and avoids paying for durability that will never be used.
When this WOULD be correct
This option would be correct if the question asked for a high-performance data disk for a production VM running I/O-intensive workloads, where the disk must persist across VM deallocations and be attached as a data disk.
- ✗
A shared disk attached to multiple VMs.
Why it's wrong here
Azure shared disks are designed for clustered workloads such as SQL Server Failover Cluster Instances or Scale-Out File Server, where multiple VMs need concurrent read/write access to the same storage volume. An OS disk must be dedicated to a single VM and cannot be shared; each VM boots from its own unique OS disk, and shared disks are intended as data disks only. Choosing a shared disk would not satisfy the requirement for a single development VM and would introduce cluster complexity without improving OS disk latency.
When this WOULD be correct
A shared disk is correct when the question asks for a shared storage solution for a failover cluster or a horizontally scaled application where multiple VMs need concurrent read/write access to the same data disk, such as for SQL Server FCI or Scale-Out File Server.
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 disk.Correct answer▾
Why this is correct
An ephemeral OS disk is the best match because it provides very fast local storage for the operating system and does not need to preserve data after deallocation. This is ideal for rebuildable development VMs where performance matters more than retaining the OS disk contents.
✗A Standard HDD managed OS disk.Wrong answer — click to see why▾
Why this is wrong here
A Standard HDD managed OS disk persists its contents even after VM deallocation, which contradicts the requirement that disk contents do not survive deallocation. Ephemeral OS disks are designed to be temporary and are lost on deallocation.
★ When this WOULD be the correct answer
This option would be correct for a development VM that needs to retain its OS disk data across deallocations (e.g., to preserve installed tools or configurations) and has low cost as a priority, with no need for high performance.
Why candidates choose this
Candidates may think Standard HDD is the cheapest option and suitable for development, overlooking the specific requirement that disk contents should not survive deallocation, which is a key feature of ephemeral disks.
✗A premium managed data disk used as the OS disk.Wrong answer — click to see why▾
Why this is wrong here
A premium managed data disk cannot be used as an OS disk in Azure; OS disks must be managed disks attached as OS disks, not data disks. Additionally, premium disks are overkill for a development VM that is rebuilt often and does not need persistence.
★ When this WOULD be the correct answer
This option would be correct if the question asked for a high-performance data disk for a production VM running I/O-intensive workloads, where the disk must persist across VM deallocations and be attached as a data disk.
Why candidates choose this
Candidates may confuse 'premium' with 'better' for all scenarios, or mistakenly think a data disk can serve as an OS disk, overlooking Azure's disk type restrictions.
✗A shared disk attached to multiple VMs.Wrong answer — click to see why▾
Why this is wrong here
A shared disk cannot be used as an OS disk; it is only for data disks and requires cluster-aware file systems, so it cannot host the VM's operating system.
★ When this WOULD be the correct answer
A shared disk is correct when the question asks for a shared storage solution for a failover cluster or a horizontally scaled application where multiple VMs need concurrent read/write access to the same data disk, such as for SQL Server FCI or Scale-Out File Server.
Why candidates choose this
Candidates may confuse 'shared' with 'ephemeral' or think that attaching a disk to multiple VMs could provide redundancy or cost savings for development, not realizing the OS disk attachment limitation.
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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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.