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HA & DR Concepts


What is HA? And Why Is HA used?

HA: - High Availability. We use High Availability technique to keep the database always online, and always available to the users, without any human interventions the databases will failover from one node to another to keep the databases available always.

What is DR? And Why is DR used?

DR: Disaster Recovery. We use Disaster Recovery technique to keep the data in database safe and databases available to the users, only with the human intervention the databases will failover from one node to another to keep the data and database available always.

  • The main difference between HA and DR is, In HA the database will flip/failover from one node to another without any human interventions, but in DR the databases will flip/failover only with human interventions.

Some of the HA and DR techniques in SQL server are:

  1. Log Shipping – DR Plan
  2. Mirroring – can be a HA or DR
  3. Replication – DR Plan
  4. AOAG – Always on Availability Group – Can be a HA or DR
  5. Clustering – Can be a HA 

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