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DAG : FSW Failed Query

    Question

  • Hi Team

    In my test lab, there are two mailbox server which under DAG configured. My FSW has been configured in my Hub Transport server.

    I was being tested like to remove the share in the FSW folder directory and removed the shared in the HUB transport server and obioulsy MBX servers lost the quorum

    All good up to this

    Again i was shared the FSW folder in hubstransport server and given the  full control permision to everyone and administrator

    All back to working again, i can able to move the databse between the servers, but whenever i use the command and i was getting the below WARNING saying

    Get-DatabaseAvailabilityGroup -Identity KBDAG -Status

    WARNING: Database availability group 'KBDAG' witness is in a failed state. Thedatabase availability group requires the witness server to maintain quorum.Please use the Set-DatabaseAvailabilityGroup cmdlet to re-create the witnessserver and directory.

    Name             Member Servers                                      Operational Servers
    ----             --------------                                      -------------------
    KBDAG            {KBLABMBX02, KBLABMBX01}                            {KBLABMBX01, KBLABMBX02}

    so i issued the below command to rectified in the HUB Server

    Set-DatabaseAvailabilityGroup -Identity kbdag -WitnessDirectory C:\Dagfsw

    Now coming to the query, Even Though the witness was in failed state, how the database can move between the servers. I would like to know this

    Please help me. all working fine now, but i would like to know, howcome the database was moved between the servers even though the witness was failed


    ramakrishnan

    Saturday, June 02, 2012 3:06 PM

Answers

  • Hi,

    Yes, you are correct. If cluster service is online, client can communicate with Exchange Servers.

    Please understand that when we create DAG, it will initially use the Node Majority quorum model. When the second Mailbox server is added to the DAG, the quorum is automatically changed to a Node and File Share Majority quorum model. When this change occurs, the DAG begins using the witness server for maintaining a quorum. If the witness directory doesn't exist, Exchange automatically creates it, shares it, and provisions the share with full control permissions for the cluster network object (CNO) computer account for the DAG.

    The quorum model change should happen automatically. However, if the quorum model doesn't automatically change to the proper model, you can run the Set-DatabaseAvailabilityGroup cmdlet with only the Identity parameter to correct the quorum settings for the DAG.

    Exchange 2010 – File Share Witness oddities…

    http://blogs.technet.com/b/timmcmic/archive/2010/07/13/exchange-2010-file-share-witness-oddities.aspx


    Xiu Zhang

    TechNet Community Support

    • Marked as answer by rush2ramki Wednesday, June 06, 2012 3:34 PM
    Tuesday, June 05, 2012 6:29 AM
  • HI Leif

    Thanks leif, is there any documnet for cluster failover between Even and Odd number DAG Member sever

    I mean, i would like to know the behavaiour of Even and Odd Numbers DAG member servers in DAG

    How they work in evan and odd and what is the difference between them

    Currently am having 2 DAG members in my test laband iwould like to add more after know this

    Thanks in advince.


    ramakrishnan

    • Marked as answer by rush2ramki Wednesday, June 06, 2012 3:34 PM
    Sunday, June 03, 2012 7:48 AM

All replies

  • Hi,

    The witness directory has nothing to do with moving databases.

    You can always move active databases between 2 MBX servers if cluster service is running on these and they are part of a DAG.

    The sole purpose of the witness directory is to make sure that one of the MBX servers can get quorum and thereby mount the databases if the other MBX server is dead.

    In addition: the FSW is not needed as long as both MBX servers are running and they can communicate with each other

    Leif


    Saturday, June 02, 2012 4:11 PM
  • Hi Leif

    Thanks for your info.

    Coming to this Scenario, if FSW and One of the MBX servers (mbx1) (mbx1 and Mbx2) server went offilne.

    I belive Database  from MBX1 cannot move to MBX2 server which is onlince , Monted Server is Blank when MBX1 and FSW is down

    Users using MAPI and OWA in Database of MBX1 server  is being down right

    Correct me if am wrong


    ramakrishnan

    Sunday, June 03, 2012 7:19 AM
  • Hi,

    If the FSW server and one of the MBX servers are down no users would be able to access their mailboxes (the remaining MBX server can't get quorum and therefore the cluster goes down and all databases will be dismounted).

    In the above case you will need to perform manual some procedures as described here:

    http://technet.microsoft.com/en-us/library/dd351049.aspx

    Leif

    Sunday, June 03, 2012 7:25 AM
  • HI Leif

    Thanks leif, is there any documnet for cluster failover between Even and Odd number DAG Member sever

    I mean, i would like to know the behavaiour of Even and Odd Numbers DAG member servers in DAG

    How they work in evan and odd and what is the difference between them

    Currently am having 2 DAG members in my test laband iwould like to add more after know this

    Thanks in advince.


    ramakrishnan

    • Marked as answer by rush2ramki Wednesday, June 06, 2012 3:34 PM
    Sunday, June 03, 2012 7:48 AM
  • Hi,

    There is not a big difference in the behaviour of MBX servers in a DAG in an even or an odd number DAG.

    The difference is that in an even number DAG the FSW might be needed to form quorum (majority) where in an odd number DAG the FSW is not needed (or used) for that.

    Leif

    Sunday, June 03, 2012 12:08 PM
  • HI Leif

    So as per the update, odd numbers does not require to contact FSW regarless of members count like 1,3,7 9..etc...

    and database can move the between the servers eventhough the FSW is down in ODD numbers Dag Members

    Right


    ramakrishnan

    Sunday, June 03, 2012 1:13 PM
  • Hi,

    Yes, you are correct. If cluster service is online, client can communicate with Exchange Servers.

    Please understand that when we create DAG, it will initially use the Node Majority quorum model. When the second Mailbox server is added to the DAG, the quorum is automatically changed to a Node and File Share Majority quorum model. When this change occurs, the DAG begins using the witness server for maintaining a quorum. If the witness directory doesn't exist, Exchange automatically creates it, shares it, and provisions the share with full control permissions for the cluster network object (CNO) computer account for the DAG.

    The quorum model change should happen automatically. However, if the quorum model doesn't automatically change to the proper model, you can run the Set-DatabaseAvailabilityGroup cmdlet with only the Identity parameter to correct the quorum settings for the DAG.

    Exchange 2010 – File Share Witness oddities…

    http://blogs.technet.com/b/timmcmic/archive/2010/07/13/exchange-2010-file-share-witness-oddities.aspx


    Xiu Zhang

    TechNet Community Support

    • Marked as answer by rush2ramki Wednesday, June 06, 2012 3:34 PM
    Tuesday, June 05, 2012 6:29 AM
  • Thanks for all your updates


    ramakrishnan

    Wednesday, June 06, 2012 3:34 PM