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Automatic failover in AlwaysOnHighAvailability RRS feed

  • Question

  • Hi,

    Does AlwaysOn supports automatic failover when 

    1] primary server shut down unexpectedly .

    2] By stopping MSSQLSERVER service from services option.

    Does Mirroring with witness server supports above two scenarios with automatic failover.

    Thanks,

    Ni3.

    Friday, November 30, 2018 10:50 PM

Answers

  • Hi,

    Yes. Always On supports failover in the first case you've mentioned, however, I have doubt that it won't do the failover as it's considered the intentional operation. For mirroring to work with automatic failover you will have to have DBM with the synchronous mode. Just in case you are interested how it works read this document. 

    Hope this helps

    Thank you



    Hemantgiri S. Goswami | SQL Server Consultant
    SQL Server Citation | Twitter | Facebook
    Author of the book - SQL Server 2008 High Availability



    • Edited by Hemantgiri Goswami Monday, December 3, 2018 7:45 AM
    • Marked as answer by Ni3NB Monday, December 3, 2018 10:36 AM
    Monday, December 3, 2018 7:29 AM

All replies

  • For AlwaysOn:

    Yes. As long as you your databases syched in synchronous mode, have a witness setup, Availability group is set to automatic fail over, and a quorum can be reached, services will fail over in the above scenarios.

    For Mirrorring:

    Yes. If you are running the in High safety (Synchronous mode), and the mirrored database is already synchronized, and the principal server lost communication with rest of the mirroring configuration, which the mirror server and witness can retain the quorum.

    https://docs.microsoft.com/en-us/sql/database-engine/database-mirroring/role-switching-during-a-database-mirroring-session-sql-server?view=sql-server-2017#ConditionsForAutoFo

    Friday, November 30, 2018 11:02 PM
  • 1) The primary replica and one secondary replica are configured for synchronous-commit mode with automatic failover.

    https://social.technet.microsoft.com/wiki/contents/articles/37872.sql-server-installation-on-centos-linux.aspx

    Saturday, December 1, 2018 6:04 AM
  • With AO there is no need to setup witness.....

    Best Regards,Uri Dimant SQL Server MVP, http://sqlblog.com/blogs/uri_dimant/

    MS SQL optimization: MS SQL Development and Optimization
    MS SQL Consulting: Large scale of database and data cleansing
    Remote DBA Services: Improves MS SQL Database Performance
    SQL Server Integration Services: Business Intelligence

    Sunday, December 2, 2018 5:36 AM
  • Hi,

    Yes. Always On supports failover in the first case you've mentioned, however, I have doubt that it won't do the failover as it's considered the intentional operation. For mirroring to work with automatic failover you will have to have DBM with the synchronous mode. Just in case you are interested how it works read this document. 

    Hope this helps

    Thank you



    Hemantgiri S. Goswami | SQL Server Consultant
    SQL Server Citation | Twitter | Facebook
    Author of the book - SQL Server 2008 High Availability



    • Edited by Hemantgiri Goswami Monday, December 3, 2018 7:45 AM
    • Marked as answer by Ni3NB Monday, December 3, 2018 10:36 AM
    Monday, December 3, 2018 7:29 AM