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  • Moving to Exchange 2010

    Hi,

    We have a small environment (about 150 users) with single virtualized Exchange 2007 server running in 2 node VMware ESXi 4.1 cluster.

    Now we are planning to upgrade Exchange to 2010 -version.

    I was thinking that maybe it would be a good idea to use DAG and install two Exchange 2010 servers. That would give us more reliable email system.

    I have read that in this 2 member DAG configuration we are going to need a hardware load balancer to get things work. I see that there will be one major problem in this configuration. If that HLBL goes down then our email systems are down. It would be a single point of failure. Right?



    Thanks in advance!

  • #2
    Re: Moving to Exchange 2010

    The DAG is just for the databases.
    For client access, you would need to use a HLB because you cannot use WLB unless you have additional servers.

    Furthermore, the clients connect to the HLB via an internal only DNS record which points to a unique host name known as an RPC CAS Array. If your HLB was to go down then you can take that DNS record and point it at one of the CAS role servers directly.

    It is not a hard requirement to use a load balancer though. If you are simply replicating the data off site through the DAG, then you can have the clients follow later on by changing the DNS entry.

    Whatever you decided to do, configure the RPC CAS array right at the start, even if the DNS entry goes straight to a CAS role holder. Trying to retro-fit the CAS Array once you have done live is a lot of work (all clients have to be touched).

    Simon.
    --
    Simon Butler
    Exchange MVP

    Blog: http://blog.sembee.co.uk/
    More Exchange Content: http://exchange.sembee.info/
    Exchange Resources List: http://exbpa.com/
    In the UK? Hire me: http://www.sembee.co.uk/

    Sembee is a registered trademark, used here with permission.

    Comment


    • #3
      Re: Moving to Exchange 2010

      Originally posted by Sembee View Post
      The DAG is just for the databases.
      For client access, you would need to use a HLB because you cannot use WLB unless you have additional servers.

      Furthermore, the clients connect to the HLB via an internal only DNS record which points to a unique host name known as an RPC CAS Array. If your HLB was to go down then you can take that DNS record and point it at one of the CAS role servers directly.

      It is not a hard requirement to use a load balancer though. If you are simply replicating the data off site through the DAG, then you can have the clients follow later on by changing the DNS entry.

      Whatever you decided to do, configure the RPC CAS array right at the start, even if the DNS entry goes straight to a CAS role holder. Trying to retro-fit the CAS Array once you have done live is a lot of work (all clients have to be touched).

      Simon.
      Thank you Simon for your answer. That was very helpful.

      Why is that CAS Array so important?

      I think we dont need the HLB.

      If I install and configure 2 member DAG (e.g Exchange1 and Exchange2) and create CAS Array. Cas Array DNS will point to Exchange1. If Exchange1 goes down I can configure the CAS Array DNS entry to Exchange2?

      Comment


      • #4
        Re: Moving to Exchange 2010

        It is important because of the change of architecture of Exchagne 2010.
        The clients point to the CAS role server, not the mailbox role.
        If you have a DAG and fail over to the other server, the clients DO NOT follow. The CAS array allows you to change a DNS entry and the clients will then connect to the other server.

        This new blog posting explains more:

        http://blogs.technet.com/b/exchange/...ct-part-1.aspx

        Simon.
        --
        Simon Butler
        Exchange MVP

        Blog: http://blog.sembee.co.uk/
        More Exchange Content: http://exchange.sembee.info/
        Exchange Resources List: http://exbpa.com/
        In the UK? Hire me: http://www.sembee.co.uk/

        Sembee is a registered trademark, used here with permission.

        Comment

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