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Exchange 2010 CAS Array question

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  • Exchange 2010 CAS Array question

    I've been asked about setting up a CAS array in the following configuration --- can anyone see any potential issues?

    2 Physical Sites but both in single AD site
    1Gbps link between sites -- typical Ping <1ms
    Both sites on same subnet
    1 Mailbox server at each site -- members of same DAG
    3 CAS/HT servers total, 2 at one site, 1 at the other

    Since the speed of the site link is so high, I cannot see any issues with a single CAS array spanning both physical sites, but will bow to more expert opinion
    Last edited by Ossian; 22nd September 2011, 10:29.
    Tom Jones
    MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
    PhD, MSc, FIAP, MIITT
    IT Trainer / Consultant
    Ossian Ltd
    Scotland

    ** Remember to give credit where credit is due and leave reputation points where appropriate **

  • #2
    Re: Exchange 2010 CAS Array question

    What is the CAS array going to point to?
    A CAS array is just a DNS entry, so it points to a DNS record.

    Are you using a load balancer or anything? Otherwise all I can see is that you would have all CAS traffic either going to one or other of the servers, or if both servers were in DNS, completely random. For that I see zero point.

    What happens if the link drops? Some clients will work, some will not.

    Although I wouldn't have two physical sites in the same AD site, but I am funny like that.

    Simon.
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    Simon Butler
    Exchange MVP

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    • #3
      Re: Exchange 2010 CAS Array question

      Sorry, should have said -- Windows NLB between the 3 CAS servers

      I've been assured the link is "highly reliable"

      AD structure is existing and won't be changed
      Tom Jones
      MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
      PhD, MSc, FIAP, MIITT
      IT Trainer / Consultant
      Ossian Ltd
      Scotland

      ** Remember to give credit where credit is due and leave reputation points where appropriate **

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      • #4
        Re: Exchange 2010 CAS Array question

        If the connection between the two sites is anything other than a direct cable which involves no other party, then I am sorry, I don't consider it to be reliable.

        Previous behaviour is not an indication of future behaviour, particularly if BT are involved anywhere, or it uses cable and copper stays at the current high price.
        Too many people plan for everything working correctly all the time, rather than planning for things to break. While a CAS array will work correctly in the way that you have planned for probably 95% of the time, you can guarantee that some donkey with a JCB will break a cable and the person who's Outlook is connected to the remote side will be the one who signs the cheques.

        If they will not change the AD structure then I don't think you have any option but to use a single CAS array, as I think it is one CAS array per site. There is certainly a link between CAS array and AD site, but I haven't tried setting up two CAS arrays in the same site to know if that is an issue.

        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.

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        • #5
          Re: Exchange 2010 CAS Array question

          OK, thanks
          Will discuss further with the client.
          Tom Jones
          MCT, MCSE (2000:Security & 2003), MCSA:Security & Messaging, MCDBA, MCDST, MCITP(EA, EMA, SA, EDA, ES, CS), MCTS, MCP, Sec+
          PhD, MSc, FIAP, MIITT
          IT Trainer / Consultant
          Ossian Ltd
          Scotland

          ** Remember to give credit where credit is due and leave reputation points where appropriate **

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