Azure Site Recovery (ASR) and Availability Zones – Configuration & Operations Guide

Part 1: Azure Site Recovery (ASR)

📘 What is Azure Site Recovery?

Azure Site Recovery (ASR) is Microsoft’s disaster recovery-as-a-service (DRaaS) solution. It helps you replicate, fail over, and recover workloads—including VMs, physical servers, and Azure VMs—to a secondary location during outages.

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🛠️ ASR Key Components

Component	Purpose
Source Environment	Where the protected workloads reside
Recovery Services Vault	Central hub for managing backup and replication
Replication Policy	Defines RPO, recovery points, and retention
Process Server	For physical/VMs in on-prem replication
Configuration Server	Coordinates replication (on-prem to Azure)

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✅ ASR Supported Scenarios

• On-premises → Azure
• Azure region → Azure region
• VMware/Hyper-V → Azure
• Physical servers → Azure

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📋 ASR Configuration Steps

🔹 Scenario: On-premises to Azure (VMware/Physical)

1. Create a Recovery Services Vault
   • Azure Portal → Search “Recovery Services Vault” → Create
2. Set up Site Recovery
   • In the vault → Site Recovery → Choose source (On-prem) and target (Azure)
3. Download & Install Configuration Server
   • Install on a dedicated Windows server (must be domain-joined)
4. Register Configuration Server
   • Use vault credentials to register it to Azure
5. Install Mobility Agent
   • Install on each source machine to replicate
6. Create Replication Policy
   • Define RPO (Recovery Point Objective), app-consistent snapshots, and retention
7. Enable Replication
   • Map source to target resource group, subnet, and VM size
8. Test Failover
   • Perform a test failover to validate replication (no production impact)
9. Planned / Unplanned Failover
   • Switch to Azure in case of disaster, choose direction of failback

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🔁 Azure-to-Azure Replication

1. Select the source Azure VM
2. Choose target region
3. Configure network mapping, disks, and VM sizes
4. Enable replication, monitor health and perform test failovers

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📊 ASR Monitoring and Operations

• Recovery Services Vault Dashboard → See replication health, events, jobs
• Azure Monitor + Log Analytics → Alerts and automation
• Cost optimization → Use Reserved Instances for secondary region

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🔹 Part 2: Azure Availability Zones

📘 What are Availability Zones?

Availability Zones are physically separate datacenters within an Azure region. Each zone has independent power, cooling, and networking to ensure high availability.

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🛡️ Benefits of Using Availability Zones

• Protect against datacenter-level failures
• Provide 99.99% uptime SLA for zone-redundant services
• Ensure resiliency and fault isolation

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🏗️ Availability Zones Architecture

• Zone 1, Zone 2, Zone 3 → Each with isolated infra
• Services like VMs, managed disks, load balancers, databases can be spread across zones

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🔧 Configuring Availability Zones

For Azure VMs:

1. During VM creation → Choose the region with support for Zones
2. Select a specific zone (1, 2, or 3) or use zone balancing
3. Use Availability Sets if deploying across fault and update domains (within a zone)

For Load Balancing:

• Use Standard Load Balancer to direct traffic across multiple zones
• Zone-aware frontend and backend pool

For Data:

• Use Zone-Redundant Storage (ZRS) for blob storage to replicate data across zones
• Use Azure SQL zone-redundant deployments for HA

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🔄 ASR + Availability Zones – Combined Resilience

• ASR replicates across regions (Geo-resilience)
• AZs provide intra-region redundancy
• For full DR: Deploy zone-redundant VMs + enable ASR to replicate to another region

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🧠 Best Practices

• Use Proximity Placement Groups (PPG) for low latency when needed
• Schedule test failovers quarterly
• Monitor RTO/RPO compliance
• Tag all resources for DR drill tracking