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Difference between High Availability and Disaster Recovery

25 April,2019 by Tom Collins

Question: What is the difference between High Availability (HA) and  Disaster Recovery (DR)? I often hear these terms being used interchangeably ,and would like to hear some specific definitions .

Answer:  High Availability  and Disaster Recovery  are often interchanged but there is a difference - and once we define the attributes of both High Availability and Disaster Recovery  , you can then use them accordingly.   

HA is a system feature , with an objective to achieve an agreed operational uptime for a higher than normal period

DR refers to procedures and policies to facilitate recovery of critical systems and infrastructure supporting those systems - in reaction to a disaster  . Typically a disaster is "declared" and the DR procedures are enforced.

Both DR and HA can be challenging, it is not always easy to foresee every situation. Organizations invest significant time and money into designing HA and DR systems - repeatedly simulating HA failover and DR scenarios.

SQL Server system redundancy and high availability       is all about identifying the HA stack such as physical locations, electricity, servers, database layer , then agreeing on the level of redundancy you want to build. The level of redundancy you is dependent on factors such as expertise, cost , and service level agreements .

Creating a Disaster Recovery Plan    requires analysis  of typical causes of downtime and then understanding the impact \ consequences of downtime on the organization.






Author: Tom Collins (


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