How Should You Back Up Failover Cluster Drives P and S in Azure?
Short answer
For drive P, select an Azure Backup enhanced policy with selective disk backup enabled; for drive S, select Azure Disk Backup, which supports shared Premium SSDs with crash-consistent snapshots.
Question
You have an Azure subscription. The subscription contains multiple virtual machines that run Windows Server and host Failover Clustering workloads. Each cluster contains the drives shown in the following table.
You need to recommend a backup solution for drives P and S. The solution must meet the following requirements:
• The backup of drive P must be application-consistent.
• The backup of drive S must be crash-consistent.
• Costs must be minimized.
What should you include in the recommendation for each disk? To answer, select the appropriate options in the answer area.
NOTE: Each correct selection is worth one point.
Key Takeaways
The exam tests whether you can separate application consistency (VM-level enhanced policy with VSS) from crash consistency (block-level Azure Disk Backup) and then trim cost with selective disk backup rather than protecting every disk.
This AZ-305 hotspot asks you to pick a cost-minimized Azure backup approach for two cluster drives: drive P must be application-consistent and drive S only crash-consistent. The page confirms that drive P maps to an Azure Backup enhanced policy with selective disk backup, while drive S maps to Azure Disk Backup for shared Premium SSDs.
Common mistake: The most common wrong approach is to back up the entire VM (or use the default policy) for both drives, which either fails the application-consistent requirement for drive P or needlessly protects non-required disks and inflates cost, and to assume Azure Disk Backup can deliver application consistency.
Expert Analysis
Why the Answer Is Correct
Drive P hosts a Failover Clustering workload that requires an application-consistent recovery point, and only a VM-level Azure Backup policy in enhanced mode triggers the Windows VSS writer chain to quiesce the application before the snapshot. Because the subscription holds many disks that are not part of the requirement, the enhanced policy should have selective disk backup enabled so only drive P is protected, which is exactly the cost-minimization lever the question is pointing at. Drive S is a cluster shared disk; Azure Disk Backup snapshots managed disks at the block storage tier, supports shared Premium SSDs, and produces crash-consistent recovery points, which satisfies the requirement without paying for a full VM backup. Pairing the two services gives application consistency where it is mandated and the cheaper block-level protection where only crash consistency is needed.
Why Other Candidate Answers Are Wrong
The default (standard) VM backup policy on a Windows VM yields file-system-consistent snapshots, not application-consistent ones, so it does not satisfy drive P's requirement. Protecting the whole VM with all disks attached meets consistency but violates the cost requirement, since drives with no backup requirement would be included. Using Azure Disk Backup for drive P is wrong because disk backup is crash-consistent only, and Azure Site Recovery is a replication/disaster-recovery service, not a per-disk backup that produces application-consistent recovery points. Backing up the cluster shared volume through the VM-level policy is also unreliable, because VM backup cannot consistently snapshot shared disks attached to multiple cluster nodes.
Community Comment Notes
As gpais noted, drive P is served by "an enhanced policy that has selective disk backup enabled", which is precisely the combination of consistency plus cost control the scenario asks for. The same commenter pointed out for drive S that "Azure Disk Backup explicitly supports shared Premium SSDs at the block storage tier", confirming the shared cluster disk is in scope for disk-level snapshots. That community reading matches the vendor documentation and the exam's intent, so the pairing of enhanced policy (P) plus Azure Disk Backup (S) is the verdict this page publishes.
Official Reference
https://learn.microsoft.com/en-us/azure/backup/backup-managed-disks
This link opens the official vendor documentation in a new tab.
Exam Strategy
Read the consistency wording first: "application-consistent" always pulls you toward a VM-level Azure Backup policy (enhanced policy with VSS), while "crash-consistent" on a shared or standalone disk points to Azure Disk Backup. Then apply the cost clause as a filter — if only one drive matters, enable selective disk backup instead of backing up every disk on the VM.
Frequently Asked Questions
Why can't Azure Disk Backup be used for drive P instead of an enhanced VM backup policy?
Does Azure Disk Backup support the cluster shared disk used for drive S?
Discussion 1 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 1
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gpais 👍 1drive P : • An enhanced policy that has selective disk backup enabled drive S: is a cluster Shared disk. Azure Disk Backup explicitly supports shared Premium SSDs at the block storage tier.
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