DFS failover delay

Discussion in 'File Systems' started by systems, Jul 8, 2008.

  1. systems

    systems Guest

    Hello

    I have configured DFS in a test environment with 3 DFS namespace hosts for
    fault tolerance. Replication groups have also been setup with the data
    replicating between each of the 3 hosts. Each host is located at a different
    site though they are connected by high speed links.
    Whilst all 3 DFS namespace hosts are online, access to the DFS folder
    structure works perfectly. However, if a host is taken offline, client pcs
    located on the same site experience 15-30 second delays in accessing the DFS
    root and folder targets (at another site), eg, \\contoso.com\public\example.
    This delay is repeated even once the client pc is connected and is browing
    sub folders. If the clients connect without using the DFS namespace eg,
    \\server\shared\example the connection is instantaneous. Client pcs located
    at the other sites are uneffected.
    As soon as the offline server is brough back online service resumes
    immediately. Any ideas what could be causing these delays?

    Many thanks
     
    systems, Jul 8, 2008
    #1
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  2. systems

    DaveMills Guest

    I have seen this sort of thing on a single site. The DFS client seems to query
    the servers in order and waits for a timeout before checking the next server.
    What's more Windows Explorer seems to lock up while it waits. This can be very
    frustrating for the users. (and the help desk)

    It is a bit like NT4 DNS looks were with 60 sec timeouts. In W2k DNS fired of
    the second request just a second or 2 after the first and then accepted the
    first answer to be returned. I think DFS would be vastly improved by a similar
    algorithm.
     
    DaveMills, Jul 8, 2008
    #2
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  3. systems

    systems Guest

    Thanks for the suggestion Dave.

    I configured another DFS namespace host at one site and then tested. It
    seems that whichever namespace host the client PC has as the first in it's
    referral list always needs to be online. If this host is taken offline then
    there is a delay in connection, even if there is another DFS host on the same
    LAN subnet.

    To see if there was a problem connecting to DFS hosts over a WAN I also
    removed all DFS hosts from a particular site. This forced the clients to
    connect over the WAN and there were no delays in connection.

    Any ideas why the client still tries to connect to the host that is forst in
    the referral list even if it is offline?

    Thanks

     
    systems, Jul 10, 2008
    #3
  4. systems

    DaveMills Guest

    That is my experience too.
    I guess because that is how it determines it is offline. It should be changed to
    wait only 2 seconds before trying the next in the list.
     
    DaveMills, Jul 13, 2008
    #4
  5. systems

    arkadja Guest

    i've your same problem.

    Someone know the solution?
     
    arkadja, May 5, 2009
    #5
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