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Zorluk: OrtaDesign Azure Site Recovery Solutions

An automotive manufacturing company runs a critical assembly line coordination system on Azure virtual machines in the UK South region. The system consists of two tiers:
1. An application tier with three stateless web servers (`VM-App1`, `VM-App2`, and `VM-App3`).
2. A database tier running SQL Server on a virtual machine (`VM-DB1`).

The data and log disks on `VM-DB1` have a combined write churn of 75 MB/s75\text{ MB/s}, with the transaction log disk alone reaching a continuous write churn of 60 MB/s60\text{ MB/s}. The business requires a Recovery Point Objective (RPO) of 1515 minutes and a Recovery Time Objective (RTO) of 22 hours for the entire system.

Which disaster recovery strategy should you recommend to meet the requirements?

  1. A
    Replicate all virtual machines, including the database server, to the target region using Azure Site Recovery with a high-churn replication policy.
  2. B
    Configure Azure Backup with Cross-Region Restore enabled to perform hourly backups of all virtual machines, and restore them in the secondary region in the event of a disaster.
  3. Replicate the application tier virtual machines using Azure Site Recovery, and configure SQL Server Always On Availability Groups to replicate the database to the target region.Cevap
  4. D
    Configure Read-Access Geo-Redundant Storage for the virtual machine disks, and manually create new virtual machines in the target region using the read-only disk copies during a failover.

Cevap

Replicate the application tier virtual machines using Azure Site Recovery, and configure SQL Server Always On Availability Groups to replicate the database to the target region.
The correct strategy uses Azure Site Recovery for the application tier virtual machines, which fall well within supported limits, and SQL Server Always On Availability Groups for the database tier. Azure Site Recovery enforces a maximum write churn limit of 54 MB/s54\text{ MB/s} per disk for Premium SSDs under the high-churn replication policy. Because the database transaction log disk has a continuous write churn of 60 MB/s60\text{ MB/s}, block-level replication via Azure Site Recovery will fail. Using SQL Server Always On Availability Groups provides database-level replication that bypasses these storage-tier limits while meeting the 1515-minute RPO and 22-hour RTO.

Adım Adım Çözüm

1
Evaluate the write churn requirements of the database tier virtual machine against Azure Site Recovery limits.
The database transaction log disk has a continuous write churn of 60 MB/s60\text{ MB/s}, which exceeds the maximum supported limit of 54 MB/s54\text{ MB/s} per disk for Azure Site Recovery (even with the high-churn replication policy enabled).
This establishes that the database virtual machine cannot be replicated as-is using Azure Site Recovery block-level replication.
2
Determine the optimal disaster recovery mechanism for the SQL Server database tier.
SQL Server Always On Availability Groups replicates database transactions directly at the SQL application layer, bypassing Azure Site Recovery block-level disk limits, and satisfies the near-zero data loss (RPO) and fast failover (RTO) requirements.
To select a replication technology that natively supports high-churn database workloads and meets the strict RTO and RPO requirements.
3
Determine the optimal disaster recovery mechanism for the stateless web application tier.
The application tier VMs (`VM-App1`, `VM-App2`, and `VM-App3`) are stateless and have low write churn, making them ideal candidates for standard Azure Site Recovery replication.
To minimize replication cost and administrative overhead for non-database workloads while securing VM orchestration and failover capabilities.

Anahtar Kavram

Disaster recovery design involving mixed workloads with high write churn that exceed Azure Site Recovery limits.
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Design Azure Site Recovery Solutions

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