A logistics company hosts a maritime cargo tracking application on Azure virtual machines … — Microsoft Azure Solutions Architect (AZ-305)

A logistics company hosts a maritime cargo tracking application on Azure virtual machines in the East US region. The application architecture consists of the following components:

* `VM-App`: Runs the application front-end and middle-tier. It contains three Standard SSD disks, with a maximum write churn of $3\text{ MB/s}$ per disk and a total VM write churn of $8\text{ MB/s}$ .
* `VM-DB`: Runs a Microsoft SQL Server database. It contains four Premium SSD disks. The transaction log disk experiences a continuous write churn of $22\text{ MB/s}$ , and the total VM write churn is $38\text{ MB/s}$ .

You need to design a disaster recovery (DR) solution to the West US region that meets the following requirements:

* A Recovery Point Objective (RPO) of $15$ minutes or less
* A Recovery Time Objective (RTO) of $2$ hours or less

Which of the following replication strategies should you recommend? (Select TWO.)

Replicate VM-App to the West US region using Azure Site Recovery.Answer
Implement SQL Server Always On Availability Groups to replicate the databases on VM-DB to a destination VM in the West US region.Answer
C
Replicate VM-DB to the West US region using Azure Site Recovery.
D
Configure Azure SQL Database Auto-Failover Groups to replicate the databases on VM-DB to the West US region.

Answer

Replicate the application server using Azure Site Recovery, and implement SQL Server Always On Availability Groups for the database server.

The correct replication strategy uses Azure Site Recovery for the application tier VM-App, which has low disk churn (3 MB/s per disk) well within ASR limits. For the database tier VM-DB, since the write churn on the log disk (22 MB/s) exceeds ASR's disk-level limits, the database must be replicated natively using SQL Server Always On Availability Groups.

Step-by-Step Solution

Analyze the write churn metrics of the application server virtual machine (VM-App).

The write churn on VM-App is 3 MB/s per disk, and the total VM churn is 8 MB/s. Both values are within the standard limits of Azure Site Recovery (8 MB/s per Standard SSD disk).

To determine if Azure Site Recovery is a viable solution for replication of the application tier.

Analyze the write churn metrics of the database server virtual machine (VM-DB).

The log disk write churn is 22 MB/s, which exceeds the Azure Site Recovery limit for Premium SSD (10 MB/s per disk for standard, and 20 MB/s for high-churn replication).

To evaluate if VM-DB can be replicated using Azure Site Recovery without exceeding supported capacity limits.

Select replication options that satisfy both the churn limits and the 15-minute RPO / 2-hour RTO requirements.

Recommend replication via Azure Site Recovery for VM-App, and native database-level replication via SQL Server Always On Availability Groups to West US for the SQL Server workload on VM-DB.

To ensure that both tiers are replicated using supported mechanisms that meet business continuity objectives.

Key Concept

Azure Site Recovery limits require separating high-churn database workloads into native application-level replication mechanisms like SQL Server Always On Availability Groups.

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