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best witness and quorrum model for always on conf RRS feed

  • General discussion

  • hello,

    I'd like to configure always on between 2 sites (each with 2  SQL 2012 VMs )

    Need your support to understand how to configure witness and quorum for a zero downtime/

    Thanks

    Sunday, August 12, 2018 9:19 PM

All replies

  • What are the windows servers' and SQL Server versions and editions?

    What is the number of nodes in the WSFC? How many nodes will be participating in AlwaysOn AG?


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    Sunday, August 12, 2018 9:46 PM
  • hello,

    SQL server 2012

    I have 4 nodes (2 in each sites)

    would like to have the 4 of them on the always on AG

    Thanks

    Monday, August 13, 2018 2:20 PM
  • I suggest you read this:

    https://blogs.msdn.microsoft.com/john_daskalakis/2014/01/07/information-you-need-to-know-before-setting-up-geoclustering-at-sql-server-2008-or-sql-server-2012/

    Note:  There is always downtime in a failover.  There is no such thing as 0 downtime.  The duration of the downtime is dependent on many variables.  It can be a few seconds to several minutes.


    • Edited by Tom Phillips Monday, August 13, 2018 7:16 PM corrected link
    Monday, August 13, 2018 7:13 PM
  • thanks, I want to a automate as much as I can the failover.

    I have just 2 sites so the witness won't be on a third site

    Sunday, August 19, 2018 11:42 AM
  • You generally do not want automatic failover between different sites due to many factors which can affect the "heartbeat" between the sites causing unintentional failovers. 

    Monday, August 20, 2018 11:33 AM
  • thanks for your reply

    I understand this risk and I'll try to find a way to limit this.

    My question now is that is it possible to configure more than a witness: I mean a witness per datacenter

    Thanks

    Saturday, August 25, 2018 12:50 AM
  • thanks for your reply

    I understand this risk and I'll try to find a way to limit this.

    My question now is that is it possible to configure more than a witness: I mean a witness per datacenter

    Thanks

    First of all are you sure you need "zero downtime", do you really understand what is zero downtime. In AG no matter whatever model you choose you may have downtime. This is because every time primary replica is down a failover will occur and there would be some "small" downtime. So before you start anything first understand the concept.

    There is NO witness per DC, it would be single witness

    Now if you want minimum downtime then the question makes sense. So you have 4 nodes in AG in which 2 of them are on one site and other 2 on other site. For this quorum model recommended is Node and fileshare majority. The file share should not reside on any of the DC where the 2 nodes are residing it should be on 3 rd site accessible to all the 4 nodes. The best thing to do is cloud witness but it has its few limitations


    Cheers,

    Shashank

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    Saturday, August 25, 2018 5:28 AM