4.1.2. Design for Azure Site Recovery

💡 First Principle: An orchestrated, automated disaster recovery service is essential for enabling rapid and reliable failover of entire workloads to a secondary location, minimizing business disruption from regional outages.

Scenario: You are designing a DR solution for an on-premises enterprise application running on VMware VMs. This application is critical and needs to be recovered in Azure with an RTO of 4 hours and an RPO of 15 minutes in case of a regional disaster. You also need to regularly test this DR plan without impacting the production environment.

ASR is an Azure service that contributes to your disaster recovery (DR) strategy by replicating and failing over workloads to Azure or a secondary location.

Key Design Considerations:

• Replication: ASR continuously replicates data from primary sites (on-premises VMware, Hyper-V, Azure VMs) to Azure, ensuring up-to-date recovery points.
• Failover & Failback: Supports planned and unplanned failover with orchestrated recovery plans, enabling low Recovery Time Objective (RTO) and Recovery Point Objective (RPO). Failback allows workloads to return to the original site.
• Supported Workloads: Protects Azure VMs, VMware VMs, Hyper-V VMs, and physical servers, offering flexibility for hybrid architectures.
• Network Design: Facilitates IP address retention and automated DNS updates during failover, reducing reconfiguration time and ensuring seamless connectivity.
• Testing: Enables non-disruptive disaster recovery drills, allowing organizations to validate recovery plans without impacting production workloads.

⚠️ Common Pitfall: Failing to account for dependencies in a recovery plan. A recovery plan must orchestrate the startup of dependent services in the correct order (e.g., Active Directory first, then databases, then application servers) to be successful.

Key Trade-Offs:

• RPO vs. Network Bandwidth/Cost: A lower RPO (more frequent replication) requires more network bandwidth and can increase costs, especially for on-premises to Azure replication.

Reflection Question: How does designing for Azure Site Recovery (ASR), leveraging its continuous replication, orchestrated failover/failback capabilities, and non-disruptive testing, fundamentally deliver automated disaster recovery as a service, enabling rapid recovery of workloads and minimizing business disruption?