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?
Ephemeral OS disks are designed specifically for stateless workloads like temporary test VMs. The disk is hosted on the local VM storage rather than Azure Storage, providing the lowest possible read/write latency for the OS. When the VM is stopped, deallocated, or redeployed, the disk content is lost, which is exactly what you want for disposable test environments—no persistent storage cost or orphaned disks to clean up.
Why this answer
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.
Exam trap
The trap here is that candidates often choose Premium SSD (B) because they associate 'lowest latency' with premium managed disks, forgetting that ephemeral OS disks use local storage which is inherently faster and also meets the 'no persistence' requirement, while managed disks always persist data across deallocations.
Why the other options are wrong
Standard HDD managed disks have the highest latency among Azure disk types, which contradicts the requirement for the lowest practical latency. Additionally, they are persistent and survive deallocation, which is unnecessary for temporary VMs that can be rebuilt.
Premium SSD provides low latency but its data persists through deallocate, which contradicts the requirement that disk data does not need to survive deallocate. Ephemeral OS disk is the correct choice for lowest latency and data loss on deallocate.
Ultra Disk provides extremely low latency, but it is a managed disk that persists data through deallocate operations and is not ephemeral. The question requires the disk to not survive deallocation, so Ultra Disk does not meet that requirement.