An organization is designing a disaster recovery (DR) solution from the East US region to … — Microsoft Azure Solutions Architect (AZ-305)

An organization is designing a disaster recovery (DR) solution from the East US region to the West US region for an inventory management system. The system consists of two Web tier VMs (each with a $100\text{ GB}$ Premium SSD and a write churn of $0.5\text{ MB/s}$ ), two App tier VMs (each with a $128\text{ GB}$ Premium SSD and a write churn of $1.5\text{ MB/s}$ ), and one Database tier VM running SQL Server on an Azure VM. The Database VM has one OS disk with a write churn of $2\text{ MB/s}$ , one data disk with a write churn of $8\text{ MB/s}$ , and one transaction log disk with a write churn of $26\text{ MB/s}$ . All disks on the Database VM are Premium SSDs. The organization requires a target recovery point objective (RPO) of $15\text{ minutes}$ and a recovery time objective (RTO) of $2\text{ hours}$ . Which disaster recovery design should you recommend?

Replicate the Web and App tier VMs using Azure Site Recovery, and configure SQL Server Always On Availability Groups to replicate the database to a SQL Server instance running on an Azure VM in the West US region.Cevap
B
Replicate all virtual machines, including the Database VM, to the West US region using Azure Site Recovery with the high-churn replication profile enabled.
C
Replicate the Web and App tier VMs using Azure Site Recovery, and configure Azure SQL Database auto-failover groups to replicate the database tier VM to the West US region.
D
Replicate the Web and App tier VMs using Azure Site Recovery, and host the database transaction logs on a Read-Access Geo-Redundant Storage (RA-GRS) account to allow active-active database write operations in both regions.

Cevap

Replicate the Web and App tier VMs using Azure Site Recovery, and configure SQL Server Always On Availability Groups to replicate the database to a SQL Server instance running on an Azure VM in the West US region.

The correct design uses Azure Site Recovery to replicate the Web and App tier VMs, while using SQL Server Always On Availability Groups to replicate the database. This is because the Database VM's transaction log disk has a write churn of

26\text{ MB/s}

, which exceeds the maximum support limit of

20\text{ MB/s}

per Premium SSD disk for Azure Site Recovery (even with the high-churn profile enabled). Utilizing SQL Server Always On Availability Groups bypasses this ASR limitation and ensures the database is replicated with minimal latency, satisfying the

15\text{ minutes}

RPO and

2\text{ hours}

RTO.

Adım Adım Çözüm

Analyze the write churn metrics for all disks in the workload.

The Web VMs have a churn of

0.5\text{ MB/s}

per disk. The App VMs have a churn of

1.5\text{ MB/s}

per disk. The Database VM has disk churn rates of

2\text{ MB/s}

(OS disk),

8\text{ MB/s}

(data disk), and

26\text{ MB/s}

(transaction log disk). The total Database VM churn is

36\text{ MB/s}

This step evaluates whether each virtual machine and its individual disks fall within the support limits of Azure Site Recovery.

Compare disk write churn rates against Azure Site Recovery capacity limits.

The Web and App tier VMs are within both standard and high churn limits. For the Database VM, the transaction log disk's write churn of

26\text{ MB/s}

exceeds the maximum limit of

20\text{ MB/s}

per Premium SSD disk supported by Azure Site Recovery (even under the high-churn capability).

This determines that the Database VM cannot be replicated using Azure Site Recovery and requires a different disaster recovery method.

Select a disaster recovery replication strategy for the database tier that supports high write churn and meeting the RPO/RTO.

SQL Server Always On Availability Groups running on Azure VMs in the target region support replication of database transaction logs natively and can easily handle a write churn rate of

26\text{ MB/s}

while meeting the

15\text{ minutes}

RPO.

This completes the hybrid design by pairing Azure Site Recovery for the supported tiers with a native database availability solution for the high-churn SQL Server tier.

Anahtar Kavram

Azure Site Recovery (ASR) has strict write churn limits per disk (

10\text{ MB/s}

standard,

20\text{ MB/s}

high churn for Premium SSD v1) and per VM. For virtual machines running database engines with write-intensive transaction logs that exceed these limits, database-native replication mechanisms (such as SQL Server Always On Availability Groups) must be used instead of ASR.

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