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database on one server in DAG drops when internet offline

    Question

  • we have two member exchange 2013 dag group. 

    one exchange server at site 1, second at remote site 2.  witness server is at site 2.

    couple of months ago I had issue with the router at site 2, and site 2 was down.  unexpectedly the exchange server at site 1 (which was primary) dismounted the database, so email was down.  once I went to site 2, and got the router working site 1 exchange came up after a reboot.  

    well yesterday there was an internet outage for over an hour where our site 2 was located.

    and once again, this caused the exchange server at site 1 to have dismounted database.  as soon as site 2 came up again, exchange at site 1 database was mounted and everything worked fine.

    we have had this exact same setup for 2-3 years, and have tested it in the past and rebooting the exchange server at site 1 or site 2 never caused the database to dismount at site 1.

    although to be honest, we tested by rebooting one or the other server, we did not take the internet offline at either site.

    test replication-health shows everything fine, get-mailboxdatabasecopystatus also looks fine.

    do we just have something configured wrong, or is it because the witness server is at site 2?

    the tech who helped us setup the DAG recommended we place the witness server at site 2.

    Friday, July 6, 2018 8:22 PM

Answers

  • If the witness server is at site 2, a network outage will cause the database at site 1 to dismount because the server cannot contact a node majority or half the nodes plus the witness server.

    Seriously, you shouldn't consider what you've deployed to be high availability because a network outage will leave one site without service.  What you are experiencing is the way it's designed to work.


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Friday, July 6, 2018 11:54 PM
    Moderator

All replies

  • If the witness server is at site 2, a network outage will cause the database at site 1 to dismount because the server cannot contact a node majority or half the nodes plus the witness server.

    Seriously, you shouldn't consider what you've deployed to be high availability because a network outage will leave one site without service.  What you are experiencing is the way it's designed to work.


    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Friday, July 6, 2018 11:54 PM
    Moderator
  • got it.

    the 2nd site is ran by a local ISP, so I'm sure the theory is that it should never go offline.

    and in 3 years, this is the only outage they have had.

    so for HA, would moving the witness server to a third location work?


    Monday, July 9, 2018 11:46 AM
  • That might be a viable solution, but for both sites I would want to ensure that my network connection to the FSW site would be independent of the connection to the other Exchange server site.

    Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."
    Celebrating 20 years of providing Exchange peer support!

    Monday, July 9, 2018 10:04 PM
    Moderator