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Exchange 2016 DAG RRS feed

  • Question

  • Hi,

    We have data center at two sites (Site A and Site B).
    Site A has 3 Exchange 2016 servers and 1 witness server.
    Users at Site A and Site B connect to the Exchange servers at Site A.

    We are planning to setup Exchange servers at Site B so as to achieve the following:
    - If data center and wan link is up, users at Site B will connect to Exchange servers at Site B and users at Site A will connect to Exchange servers at Site A.
    - If data center at one site (example: Site A) is down, user will still be able to connect to their mailbox at the other site (example: Site B) through the wan link.
    - If data center and user network at one site (example: Site A) are down, user at that site (example: Site A) will not be able to access their mailbox

    To achieve the above do we need one DAG or two DAG ?

    Monday, June 1, 2020 9:35 AM

Answers

  • Hello,

    This can be achieved with one DAG. Add 3 more exchange servers in Site B. Segregate the Site A & Site B user's mailbox databases. Mount the Site A users mailbox databases in Site A Exchange servers and add the passive copies in Site B. Similarly, mount the Site B users mailbox databases in Site B and add the passive copies in Site B.

    Make use of all 6 exchange servers to host the active databases to distribute the load. This way, Site A users connect to the exchange servers in Site A and Site B users to Site B servers. 

    This will also address the 3 points which you have mentioned.

    https://docs.microsoft.com/en-us/exchange/high-availability/deploy-ha?view=exchserver-2016



    Thanks,
    Ashok M My blog
    ________________________________________________________________
    Please mark the reply as an answer if you find it is helpful :-)
    ________________________________________________________________

    • Marked as answer by bloss ev Tuesday, June 9, 2020 12:58 PM
    Monday, June 1, 2020 2:31 PM
  • Hi,

    Agree with Ashok, and you can deploy a cross-site DAG. When the datacenter in site A is down, datacenter failover occurs and passive db copies can be mounted in Site B.

    Additionally, please pay attention to the number of DAG members. A majority of voters must be able to communicate with each other to get the quorum. If you add 3 DAG members in Site B and the witness server is in Site A, an alternate witness server is needed in Site B. You can check this for more details about: Database availability group quorum models.

    Regards, 

    Lydia Zhou


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    • Marked as answer by bloss ev Tuesday, June 9, 2020 12:57 PM
    Tuesday, June 2, 2020 4:51 AM
    Moderator
  • Hi Lydia, Ashok,

    With 1 DAG, if the wan link between Site X and Site Y is down, are we able to achieve the following?

    -User in Site X still be able to connect to the Exchange Server at Site X and user in Site Y still able to connect to the Exchange Server at Site Y

    Thank you

    • Marked as answer by bloss ev Tuesday, June 9, 2020 12:57 PM
    Friday, June 5, 2020 3:30 AM
  • Hi BlossEv,

    If the WAN Link is down between the sites in the exchange server, then from exchange standpoint, it is considered as a site failure and data-center switchover needs to be initiated. So, all the databases will be activated on the secondary site. So all users will be connected to the Site Y.

    


    Thanks,
    Ashok M My blog
    ________________________________________________________________
    Please mark the reply as an answer if you find it is helpful :-)
    ________________________________________________________________

    Friday, June 5, 2020 6:26 AM

All replies

  • Hello,

    This can be achieved with one DAG. Add 3 more exchange servers in Site B. Segregate the Site A & Site B user's mailbox databases. Mount the Site A users mailbox databases in Site A Exchange servers and add the passive copies in Site B. Similarly, mount the Site B users mailbox databases in Site B and add the passive copies in Site B.

    Make use of all 6 exchange servers to host the active databases to distribute the load. This way, Site A users connect to the exchange servers in Site A and Site B users to Site B servers. 

    This will also address the 3 points which you have mentioned.

    https://docs.microsoft.com/en-us/exchange/high-availability/deploy-ha?view=exchserver-2016



    Thanks,
    Ashok M My blog
    ________________________________________________________________
    Please mark the reply as an answer if you find it is helpful :-)
    ________________________________________________________________

    • Marked as answer by bloss ev Tuesday, June 9, 2020 12:58 PM
    Monday, June 1, 2020 2:31 PM
  • Hi,

    Agree with Ashok, and you can deploy a cross-site DAG. When the datacenter in site A is down, datacenter failover occurs and passive db copies can be mounted in Site B.

    Additionally, please pay attention to the number of DAG members. A majority of voters must be able to communicate with each other to get the quorum. If you add 3 DAG members in Site B and the witness server is in Site A, an alternate witness server is needed in Site B. You can check this for more details about: Database availability group quorum models.

    Regards, 

    Lydia Zhou


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    • Marked as answer by bloss ev Tuesday, June 9, 2020 12:57 PM
    Tuesday, June 2, 2020 4:51 AM
    Moderator
  • Hi Lydia, Ashok,

    With 1 DAG, if the wan link between Site X and Site Y is down, are we able to achieve the following?

    -User in Site X still be able to connect to the Exchange Server at Site X and user in Site Y still able to connect to the Exchange Server at Site Y

    Thank you

    • Marked as answer by bloss ev Tuesday, June 9, 2020 12:57 PM
    Friday, June 5, 2020 3:30 AM
  • Hi BlossEv,

    If the WAN Link is down between the sites in the exchange server, then from exchange standpoint, it is considered as a site failure and data-center switchover needs to be initiated. So, all the databases will be activated on the secondary site. So all users will be connected to the Site Y.

    


    Thanks,
    Ashok M My blog
    ________________________________________________________________
    Please mark the reply as an answer if you find it is helpful :-)
    ________________________________________________________________

    Friday, June 5, 2020 6:26 AM
  • It's great that you can get useful information here. If you have any other issues about Exchange, please feel free to post in our forum.

    Have a nice day.

    Regards,

    Lydia Zhou


    Please remember to mark the replies as answers if they helped. If you have feedback for TechNet Subscriber Support, contact tnsf@microsoft.com.

    Wednesday, June 10, 2020 1:23 AM
    Moderator