AZ-305 Design business continuity solutions Practice Question
You are designing a disaster recovery solution for a multi-tier web application on Azure VMs. The solution must meet an RPO of 15 minutes and an RTO of 1 hour. The application includes a SQL Server database. Which THREE actions should you take? (Choose THREE.)
⚠ Common exam trap
Candidates often confuse Azure Backup's 1-hour backup frequency with the ability to meet a 15-minute RPO, not realizing that backup frequency is the interval between backups, not the recovery point granularity, and that synchronous replication (Always On) is required for sub-hour RPOs.
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
✓
Use Azure Premium SSD managed disks for the VMs to ensure low latency replication.
Azure Premium SSD managed disks provide low-latency, high-throughput storage that is essential for synchronous replication in SQL Server Always On Availability Groups. The synchronous commit mode requires fast disk I/O to avoid transaction delays, and Premium SSDs meet the sub-millisecond latency needed to achieve an RPO of 15 minutes and RTO of 1 hour across regions.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
Use Azure Backup for the SQL Server database with 1-hour backup frequency.
Why it's wrong here
Azure Backup creates periodic snapshots and transaction log backups, but a 1-hour backup frequency yields recovery points spaced 60 minutes apart. If a regional outage occurs, all transactions committed since the last backup are lost, directly exceeding the required 15-minute RPO. Azure Backup is a backup/disaster-recovery service, not continuous replication, so it cannot provide sub-hour recovery points unless a more frequent log shipping mechanism is used.
- ✓
Use Azure Premium SSD managed disks for the VMs to ensure low latency replication.
Why this is correct
Azure Premium SSD managed disks deliver single-digit millisecond latencies and high IOPS, which are essential for sustaining synchronous or continuous replication traffic between the primary and secondary regions without storage-level bottlenecks. When VMs are replicated via Azure Site Recovery or contain SQL Server transaction log replicas, the underlying disk performance directly influences replication lag; Premium SSD ensures that I/O operations are not throttled, helping maintain an RPO below 15 minutes. This makes Premium SSD a supported and recommended configuration for I/O-sensitive replication workloads.
- ✓
Configure SQL Server Always On Availability Groups with synchronous commit between regions.
Why this is correct
SQL Server Always On Availability Groups with synchronous commit mode synchronously copy transaction log blocks from the primary replica to the secondary replica before the transaction is committed. This guarantees zero data loss (RPO = 0) and, with a synchronous secondary configured for automatic failover, allows the database tier to automatically fail over to the secondary region within seconds. This meets and exceeds the 15-minute RPO and provides a rapid RTO, making it the correct data-tier protection mechanism.
- ✗
Deploy read-scale replicas of the SQL Server in the secondary region.
Why it's wrong here
Read-scale replicas are a feature of Azure SQL Database and SQL Server that offload read-only workloads to a secondary replica; they are not writable and cannot be promoted to become the primary database. In a disaster, read-scale replicas only serve as read targets and do not accept writes, so any un-replicated transactions in the primary would be lost and writes would be rejected, failing the RPO and RTO. Therefore, read-scale replicas are not a valid failover solution for the SQL tier.
- ✓
Configure Azure Site Recovery to replicate the web and app tier VMs to a secondary region.
Why this is correct
Azure Site Recovery (ASR) for Azure VMs continuously replicates the operating system and application data of web and app tier VMs to a secondary region, creating application-consistent recovery points every few minutes and enabling a one-click failover to a secondary region. With an RPO in the range of minutes and manageable RTO through recovery plans, ASR satisfies the 15-minute RPO requirement for the stateless/stateful web and app layers. It is often paired with data-tier replication such as Always On, as ASR is not optimized for active databases that require transaction-consistent failover.
Go deeper
Related to this question
Learn chapter
Storage Account Design Decisions
Key term
BIA and RPO RTO Design
Business Impact Analysis and the design of Recovery Point Objective and Recovery Time Objective define how much data loss and downtime a business can tolerate after an IT failure, guiding the architecture of backup and disaster recovery systems.
Key term
Azure Site Recovery
Azure Site Recovery is a Microsoft Azure service that keeps your business applications and data running by automatically replicating them to a secondary location and failing over if the primary site goes down.
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Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
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