AZ-305 Question 155
Single answerA company hosts a stateless web application that relies on external data storage and frequently scales out to handle spikes in traffic. They want to reduce both VM provisioning times and overall storage costs for their new Azure VMs. The OS disk does not need to retain any data once a VM is deprovisioned. Which VM disk configuration best meets these requirements?
- A
Use ephemeral OS disks for each VM
- B
Implement premium SSD managed disks with read/write caching
- C
Deploy standard HDD managed disks and enable read caching
- D
Attach premium SSD data disks while using unmanaged OS disks
Show answer and explanation
Correct answer: A
Explanation
Ephemeral OS disks are optimized for stateless workloads that require rapid provisioning and reimaging. Because ephemeral disks are created in the local host cache rather than in Azure Storage, deployments start up more quickly and do not incur additional disk storage costs when VMs are decommissioned. This design aligns with Microsoft-recommended best practices for modern, stateless VM architectures in Azure (see Microsoft Docs: 'Use ephemeral OS disks for Azure virtual machines').
- A. Correct.
Correct. Ephemeral OS disks are ideal for stateless scenarios where the OS state can be discarded upon deprovisioning. They significantly reduce provisioning time compared to managed disks, as the OS is hosted on the local VM cache rather than in Azure Storage. This offers faster startup and cost savings, provided persistent data is stored externally.
- B. Incorrect.
Incorrect. While premium SSD managed disks provide high performance, they are stored and persisted in Azure Storage, making provisioning times longer than ephemeral OS disks. This approach also incurs additional monthly storage costs that aren’t needed for stateless workloads.
- C. Incorrect.
Incorrect. Standard HDD managed disks are less expensive than premium SSDs, but they are still persisted in Azure Storage. Provisioning times are generally slower, and the OS disk remains in storage even after deprovisioning, which is unnecessary for stateless VMs.
- D. Incorrect.
Incorrect. Premium SSD data disks do not address the requirement to quickly provision and discard the OS. Also, unmanaged OS disks are generally not recommended for new deployments, and they would persist in storage, defeating the purpose of a stateless OS configuration.