seniorT-SQL
What is HADR (High Availability Disaster Recovery) in SQL Server?
Updated May 17, 2026
Short answer
HADR provides high availability using technologies like Always On Availability Groups and Failover Clusters.
Deep explanation
SQL Server HADR architecture ensures minimal downtime using synchronous or asynchronous replication of transaction logs. Always On Availability Groups replicate database changes to secondary replicas. Failover Cluster Instances protect instance-level availability using shared storage.
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