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  • 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.

    🛠️ ASR Key Components

    ComponentPurpose
    Source EnvironmentWhere the protected workloads reside
    Recovery Services VaultCentral hub for managing backup and replication
    Replication PolicyDefines RPO, recovery points, and retention
    Process ServerFor physical/VMs in on-prem replication
    Configuration ServerCoordinates replication (on-prem to Azure)

    ✅ ASR Supported Scenarios

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

    📋 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

    🔁 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

    📊 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

    🔹 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.

    🛡️ Benefits of Using Availability Zones

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

    🏗️ 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

    🔧 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

    🔄 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

    🧠 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