Azure Site Recovery (ASR) is a critical Disaster Recovery as a Service (DRaaS) solution that Azure Administrators use to ensure Business Continuity and Disaster Recovery (BCDR). It is designed to keep applications and workloads running during planned and unplanned outages by orchestrating replicati…Azure Site Recovery (ASR) is a critical Disaster Recovery as a Service (DRaaS) solution that Azure Administrators use to ensure Business Continuity and Disaster Recovery (BCDR). It is designed to keep applications and workloads running during planned and unplanned outages by orchestrating replication, failover, and recovery processes.
In the context of monitoring and maintenance, ASR allows administrators to replicate workloads from a primary site to a secondary location. This includes replicating on-premises physical servers, VMware, and Hyper-V VMs to Azure, or replicating Azure VMs from one Azure region to another to protect against regional failures. The service helps maintain low Recovery Point Objectives (RPO) and Recovery Time Objectives (RTO).
Key components include:
1. **Replication:** Data is continuously mirrored to the target site. Admins configure policies to define snapshot frequency and retention.
2. **Failover:** During an outage, the administrator triggers a failover, creating VMs in the target region based on replicated data to resume operations.
3. **Failback:** Once the primary site is restored, ASR synchronizes changes back to the original location.
Administrators also utilize **Recovery Plans** to group multi-tier applications, ensuring VMs start in a specific order (e.g., database before web server) and triggering Azure Automation runbooks for custom configuration. Furthermore, ASR supports **Test Failovers** (DR Drills), allowing the validation of recovery strategies in an isolated network without impacting production environments. This capability is essential for compliance and verifying that the resources are being properly monitored and maintained for high availability.
Azure Site Recovery (ASR) Guide for AZ-104
What is Azure Site Recovery (ASR)?
Azure Site Recovery is a Disaster Recovery as a Service (DRaaS) solution provided by Microsoft. While Azure Backup protects your data, Azure Site Recovery protects your applications by keeping business apps and workloads running during outages. It creates replicas of your workloads (virtual machines or physical servers) and keeps them synchronized. If your primary site goes down, you fail over to a secondary location to access your apps.
Why is it Important?
For the AZ-104 exam and real-world administration, ASR is critical for a Business Continuity and Disaster Recovery (BCDR) strategy. It helps organizations meet strict recovery goals:
• Recovery Time Objective (RTO): The duration of time within which a business process must be restored after a disaster (how fast can we get back up?). • Recovery Point Objective (RPO): The maximum acceptable amount of data loss measured in time (how much data did we lose?).
How it Works
ASR orchestrates replication, failover, and failback. It does not move the VMs technically; it replicates the disk data to a Recovery Services Vault in a secondary region or site.
1. Replication Scenarios: • Azure to Azure: Replicates Azure VMs from one Azure region to another (usually a paired region). • On-Premises to Azure: Replicates VMware VMs, Hyper-V VMs, and physical servers to Azure. • AWS to Azure: Treats AWS instances as physical servers for migration or DR.
2. The Process: • Replication: Data is continuously synced to the target location. • Failover: When the primary site fails, you initiate a failover. ASR builds VMs in the target environment using the replicated data. • Failback: Once the primary site is restored, ASR replicates the changes back to the original location and switches traffic back.
3. Key Components: • Recovery Services Vault: The storage entity in Azure that houses the replication data. • Mobility Service: An agent installed on the source VM (required for VMware and Physical servers; Azure-to-Azure uses an extension) to track data changes. • Recovery Plans: Customized plans that define the order in which machines fail over (e.g., database first, then app server, then web server).
Exam Tips: Answering Questions on Azure Site Recovery (ASR)
In the AZ-104 exam, look for specific keywords and scenarios to differentiate ASR from Azure Backup or High Availability solutions:
1. Distinguish Backup vs. ASR: If the question asks about recovering a deleted file or corrupted data, the answer is Azure Backup. If the question asks about keeping an application running during a region-wide outage or disaster, the answer is Azure Site Recovery.
2. Test Failover (Drills): Exam questions often ask how to verify DR capabilities without affecting production. The answer is a Test Failover. This creates a copy of the VM in an isolated network (sandbox) in Azure. It does not impact the live primary VM or the ongoing replication.
3. Recovery Plans are for Orchestration: If a scenario involves a multi-tier application where the SQL backend must start before the web frontend, you must select Recovery Plans. Recovery plans allow you to group VMs and add manual steps or scripts (Azure Automation Runbooks) to the boot process.
4. Regional Pairs: For Azure-to-Azure replication, Microsoft recommends using Regional Pairs (e.g., East US and West US) because they are physically isolated but connected via a high-speed network, and platform updates are staggered to prevent simultaneous downtime.
5. Failover Types: • Planned Failover: Used for expected outages (maintenance). Zero data loss implies shutting down the source machine first. • Unplanned Failover: Used during actual disasters. May result in some data loss depending on the replication frequency.