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DAG and CAS array RRS feed

  • Question

  • Dear All,
    I have 2 mailbox servers with DAG installed.
    Do you know if i can install CAS array on these 2 servers?
    Thank you,
    Tom
    Friday, December 11, 2009 6:14 PM

Answers

  • heres a good link on the loadbalancing "all-roles-installed-dag-members" :)

     

    http://www.shudnow.net/2010/03/17/exchange-2010-rtm-high-availability-load-balancing-options/

     

     

    Wednesday, June 2, 2010 11:01 PM
  • You cannot have a CAS array on your DAG, as a CAS array is really an NLB cluster, and the DAG requires failover clustering.

    You cannot have both NLB and Failover clustering on the same server.  For this reason, Microsoft's guidelines recommend using an external hardware or software load balancer.

    chris
    Friday, December 11, 2009 6:44 PM

All replies

  • You cannot have a CAS array on your DAG, as a CAS array is really an NLB cluster, and the DAG requires failover clustering.

    You cannot have both NLB and Failover clustering on the same server.  For this reason, Microsoft's guidelines recommend using an external hardware or software load balancer.

    chris
    Friday, December 11, 2009 6:44 PM
  • Correct, DAG utilize components of Windows failover-clustering and as such should not be mixed with the NLB. In this case you can use ISA server to provide the load balancing functionality and have the CAS array point to it
    Elie B

    Friday, December 11, 2009 6:54 PM
  • Can somebody put some light, or a link on how to configure ISA to provide load balancing, and to configure CAS array to point to it. Does ISA provide failover solution, if one of mail servers goes down, to redirect users to the other ones.
    Is there any cheap solution to provide failover, since for us it is much more important than load balancing.

    Thank you
    Saturday, December 12, 2009 7:24 AM
  • I never tried it with ISA but maybe this link can help you:
    http://www.isaserver.org/tutorials/Configuring_Network_Load_Balancing.html

    Elie B.
    Saturday, December 12, 2009 9:46 AM
  • You cannot have a DAG with NLB, this is correct, but that does not mean DAG and CAS arrays cannot coexist.  In this case CAS arrays would be balanced by an external source such as a hardware load balancer.

    updated to remove inaccurate comment about ISA.



    Mike Crowley
    Check out My Blog!

    Wednesday, June 2, 2010 8:17 PM
    Moderator
  • heres a good link on the loadbalancing "all-roles-installed-dag-members" :)

     

    http://www.shudnow.net/2010/03/17/exchange-2010-rtm-high-availability-load-balancing-options/

     

     

    Wednesday, June 2, 2010 11:01 PM
  • great link

    Mike Crowley
    Check out My Blog!

    Thursday, June 3, 2010 2:15 PM
    Moderator
  • Good link and i can tell you that "the poor mans version" with two servers, DAG and CAS-Array (Without NLB of course) works.

    You create a CAS-Array, make two DNS Recors for both you CAS-Servers and reduce the TTL. In case of complete failure of one server, you just delete that DNS Record an wait for TTL. When the client needs to refresh the record, he will be ansered with only the active server.

    greetings

    Thursday, March 22, 2012 10:40 AM