Azure SQL Database Disaster Recovery

Last updated: October 26, 2023

Disaster recovery (DR) for Azure SQL Database is a critical aspect of ensuring business continuity and minimizing data loss in the event of an outage or disaster. Azure SQL Database offers robust, built-in capabilities for protecting your data and applications.

Understanding Disaster Recovery in Azure SQL Database

Disaster recovery refers to the strategies and processes used to recover and protect a business's IT infrastructure in the event of a natural, man-made, or technological disaster. For Azure SQL Database, this typically involves ensuring that your data is available and can be restored with minimal downtime and data loss.

Key DR Concepts:

  • Recovery Point Objective (RPO): The maximum acceptable amount of data loss measured in time.
  • Recovery Time Objective (RTO): The maximum acceptable downtime for an application after a disaster.
  • High Availability (HA): Ensures that your database is available even during planned maintenance or unplanned outages within a single datacenter region.
  • Business Continuity (BC): The overarching strategy to ensure that critical business functions can continue during and after a disaster.

Azure SQL Database DR Capabilities

Azure SQL Database provides several features that contribute to its disaster recovery strategy:

1. Automated Backups

Azure SQL Database automatically takes full, differential, and transaction log backups of your databases. These backups are stored redundantly in Azure Storage, ensuring durability. These backups are the foundation for point-in-time restore (PITR) and long-term backup retention (LTR).

  • Point-in-Time Restore (PITR): Allows you to restore your database to a specific point in time within your backup retention period (configurable up to 35 days).
  • Long-Term Retention (LTR): Lets you configure full backup copies to be stored for longer periods (up to 10 years) in separate Azure Storage for compliance or archival purposes.

2. Geo-Restore

Geo-restore uses the geo-replicated backups to restore your database to any other Azure region. This is a crucial capability for disaster recovery scenarios where the primary region becomes unavailable. The RPO for geo-restore is typically within minutes, depending on how frequently transaction log backups are geo-replicated.

Tip:

Geo-restore is the simplest way to recover from a regional outage. It restores a copy of your database from a geo-replicated backup to a new server in any Azure region.

3. Active Geo-Replication

Active geo-replication allows you to maintain readable secondary databases in different Azure regions. These secondaries are continuously updated with changes from the primary database. This provides:

  • Fast failover: You can manually fail over to a secondary database with minimal downtime.
  • Readable secondaries: Offload read-intensive workloads to secondary replicas without impacting the performance of the primary database.
  • Lower RTO/RPO: Offers a lower RTO and RPO compared to geo-restore for critical applications that require near-continuous availability.

You can configure multiple active secondaries in different regions, and you can fail over to any of them.

4. Auto-Failover Groups

Auto-failover groups build upon active geo-replication. They allow you to manage the replication and failover of a group of databases from a primary server to a secondary server in another region. Key features include:

  • Automatic failover: Can be configured to automatically fail over databases if the primary region becomes unavailable.
  • Graceful failover: Allows for planned failovers with minimal interruption.
  • Read-write and read-only listener endpoints: Provides stable endpoints for your application, regardless of which region is active.

Important:

Auto-failover groups are the recommended solution for most disaster recovery scenarios requiring automatic or managed failover. They simplify the management of multiple databases and ensure application connectivity through stable endpoints.

Designing Your DR Strategy

When designing your disaster recovery strategy for Azure SQL Database, consider the following:

  • RTO and RPO requirements: Determine the acceptable downtime and data loss for your applications.
  • Application architecture: Understand how your application connects to the database and how it will handle failovers.
  • Cost considerations: Different DR solutions have varying costs associated with them (e.g., geo-replication incurs costs for data transfer and secondary replica resources).
  • Testing: Regularly test your disaster recovery plan to ensure it works as expected.

Example DR Scenarios:

  • Minimal downtime requirement: Use Auto-Failover Groups with active geo-replication.
  • Cost-effective DR for less critical data: Rely on Geo-Restore from automated backups.
  • Compliance and long-term archival: Implement Long-Term Retention (LTR) policies.

Getting Started

You can configure these disaster recovery features directly through the Azure portal, Azure PowerShell, or Azure CLI. Refer to the official Azure documentation for detailed step-by-step guides and best practices.

For more information on specific features, see:

Note:

This article provides an overview. Always consult the latest official Microsoft documentation for the most up-to-date information and detailed technical specifications.