An enterprise is designing a disaster recovery (DR) solution from the Germany West Central… — Microsoft Azure Solutions Architect (AZ-305)

An enterprise is designing a disaster recovery (DR) solution from the Germany West Central region to the Germany North region for a mission-critical enterprise resource planning (ERP) system. The system consists of:

* Three web and application VMs hosted on Standard_D4s_v5 instances, each with a total write churn of less than $1\text{ MB/s}$ .
* One database VM hosted on a Standard_E16s_v5 instance with the following storage configuration:
* Disk 1 (Operating System): Standard SSD ( $128\text{ GB}$ ) with a write churn of $0.5\text{ MB/s}$ .
* Disk 2 (Database Data): Premium SSD ( $1\text{ TB}$ ) with a write churn of $15\text{ MB/s}$ .
* Disk 3 (Transaction Logs): Premium SSD ( $1\text{ TB}$ ) with a write churn of $58\text{ MB/s}$ .

The total write churn for the database VM is $73.5\text{ MB/s}$ . The business requirements specify a Recovery Point Objective (RPO) of $15\text{ minutes}$ and a Recovery Time Objective (RTO) of $1\text{ hour}$ .

Which disaster recovery replication strategy should you recommend to meet the requirements while ensuring a supported technical configuration?

A
Enable Azure Site Recovery with the High Churn replication tier for all VMs, configuring write-order fidelity across the database VM disks.
B
Migrate the database to Azure SQL Database with active geo-replication, and use Azure Site Recovery to replicate the database transaction logs to Germany North.
Replicate the web and application VMs using Azure Site Recovery, and implement native database streaming replication to a standby VM in Germany North for the database tier.Answer
D
Implement Azure Backup cross-region restore (CRR) for all VMs, scheduling backup snapshots every 15 minutes.

Answer

Replicate the web and application VMs using Azure Site Recovery, and implement native database streaming replication to a standby VM in Germany North for the database tier.

The correct strategy combines Azure Site Recovery (ASR) for the low-churn web and application VMs and native database replication for the database VM. Azure Site Recovery has an absolute limit of

54\text{ MB/s}

write churn per disk, even when using the High Churn replication tier. Because the transaction logs disk has a write churn of

58\text{ MB/s}

, the database VM cannot be supported by ASR. Replicating the web/application tier with ASR and using native database replication for the database tier provides a fully supported and reliable disaster recovery solution that meets the RPO and RTO goals.

Step-by-Step Solution

Analyze the disk-level write churn metrics of the database VM.

Disk 3 (Transaction Logs) has a write churn rate of

58\text{ MB/s}

Azure Site Recovery (ASR) imposes strict thresholds on write churn per disk. Even with the High Churn tier enabled, the maximum supported write churn is

54\text{ MB/s}

per disk.

Evaluate ASR supportability for the database VM.

Since Disk 3's churn (

58\text{ MB/s}

) exceeds the

54\text{ MB/s}

limit, ASR cannot be used to replicate the database VM.

High churn rates beyond limits prevent replication from keeping up, violating RPO and causing replication health degradation.

Select the replication strategy for the low-churn VMs.

Replicate the three web/application VMs (each

< 1\text{ MB/s}

) using ASR.

Web/application VMs are well within ASR limits and can easily meet the

15\text{-minute}

RPO and

1\text{-hour}

RTO.

Select the replication strategy for the high-churn database tier.

Recommend native database replication (such as PostgreSQL streaming replication) to a target VM in Germany North.

Native database replication bypasses hypervisor-level storage replication limits, supports high transaction churn, and guarantees transactional consistency.

Key Concept

Azure Site Recovery limits and hybrid database disaster recovery design

Estimated Time:3m 0s

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