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what is witness server in exchange 2010 dag RRS feed

  • Question

  • Hi 

    Can you explain about witness server,why we use witness server in exchange dag.

    Regards

    Surendhar.J

    Thursday, November 19, 2015 6:11 AM

Answers

  • Sure.  The Exchange DAG is a Windows cluster.  As such, if there are an even number of nodes, the witness server acts as the final voting member to determine if the cluster is healthy and can be online or not.  So if you have a cluster with an even number of nodes split between two datacenters, if the datacenters can't talk to each other (some guy with the back-hoe took out the network line between the two), your cluster will still be able to be online in the datacenter where the FSW is also running.  If you have an odd number of nodes, it won't come into play, but you define it just in case you add or remove a node.

    HTH ...


    Will Martin ...
    -join ('77696c6c406d617274696e2d66616d696c6965732e6f7267' -split '(?<=\G.{2})' | ? { $_ } | % { [char][int]"0x$_" })

    Thursday, November 19, 2015 10:20 AM

All replies

  • Sure.  The Exchange DAG is a Windows cluster.  As such, if there are an even number of nodes, the witness server acts as the final voting member to determine if the cluster is healthy and can be online or not.  So if you have a cluster with an even number of nodes split between two datacenters, if the datacenters can't talk to each other (some guy with the back-hoe took out the network line between the two), your cluster will still be able to be online in the datacenter where the FSW is also running.  If you have an odd number of nodes, it won't come into play, but you define it just in case you add or remove a node.

    HTH ...


    Will Martin ...
    -join ('77696c6c406d617274696e2d66616d696c6965732e6f7267' -split '(?<=\G.{2})' | ? { $_ } | % { [char][int]"0x$_" })

    Thursday, November 19, 2015 10:20 AM
  • Hi,

    As with all DAGs that contain an even number of members, a two-member DAG requires a witness server to maintain quorum. The witness server (not pictured) is a Windows server that isn't and will never be a member of the DAG. For example, smaller organizations that use this configuration may use a file server or a directory server as the witness server. Quorum is maintained as long as more than half of the quorum voters are available and in communication. A two-member DAG with a witness server provides three quorum voters.

    I suggest you can have a look at the following article to get more useful information:

    https://technet.microsoft.com/en-us/library/dd979781(v=exchg.141).aspx

    Regards,

    David 

    Friday, November 20, 2015 1:48 AM
    Moderator