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Exchange 2010 - No DAG - Still Need HLB?

    Question

  • I have an existing Exchange 2007 system and we are going to be transitioning to Exchange 2010 later this year. We are going to have multiple CAS\HUB\MB combo servers. But, initially there will only be one copy of each database (No DAG). We will eventually add the additional storage capacity to introduce a DAG.

    Will a HLB still be required to load balance the CAS traffic?

    Friday, April 27, 2012 5:48 PM

Answers

  • It is recommended to use a Load Balancer with the CAS role regardless, yes.

    Also, you should be creating a CAS Array entry and setting that on all the mailbox databases stores before you move mailboxes to them.

    Friday, April 27, 2012 6:09 PM
  • Also, remember since you are talking about setting up a DAG in the future, do not use Windows NLB.  Windows NLB will work for you in the beginning, but as soon as you introduce a DAG, Windows NLB is incompatible with MS Failover Cluster Services, so it won't work.  See the following article:http://technet.microsoft.com/en-us/library/ff625247.aspx

    Friday, April 27, 2012 6:14 PM
  • Thank you for the feed back. Because they are multi role servers, my thought is that if user 1 is on cas\hub\mb server 1 and the CAS role on server 1 is having problems, then user 1 can connect to a different CAS server to get to his mailbox, correct? 

    Thats why you want to use a good load balancer, so that can happen seamlessly. If the Client Access Array FQDN is set on the mailbox databases and points to the Load Balancer IP in DNS, it doesnt matter if a CAS fails, the load balancer will take care of routing those client connections to the other CAS in the array.

    Correct!

    For the OP - I think looking through this would be a good use of 10 mins. It will cover off multiple things, like the fact that a CAS Array itself provides absolutely no load balancing.  Some form of load balancing is required, be it Windows NLB or 3rd party.

    http://blogs.technet.com/b/exchange/archive/2012/03/23/demystifying-the-cas-array-object-part-1.aspx

    The load balancers that have gone through the validation programme can be found here:

    http://technet.microsoft.com/en-us/exchange/gg176682


    Cheers, Rhoderick NOTICE: My posts are provided “AS IS” without warranty of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.

    Tuesday, May 01, 2012 12:28 AM

All replies

  • It is recommended to use a Load Balancer with the CAS role regardless, yes.

    Also, you should be creating a CAS Array entry and setting that on all the mailbox databases stores before you move mailboxes to them.

    Friday, April 27, 2012 6:09 PM
  • Also, remember since you are talking about setting up a DAG in the future, do not use Windows NLB.  Windows NLB will work for you in the beginning, but as soon as you introduce a DAG, Windows NLB is incompatible with MS Failover Cluster Services, so it won't work.  See the following article:http://technet.microsoft.com/en-us/library/ff625247.aspx

    Friday, April 27, 2012 6:14 PM
  • Thank you for the feed back. Because they are multi role servers, my thought is that if user 1 is on cas\hub\mb server 1 and the CAS role on server 1 is having problems, then user 1 can connect to a different CAS server to get to his mailbox, correct? 
    Friday, April 27, 2012 6:27 PM
  • Thank you for the feed back. Because they are multi role servers, my thought is that if user 1 is on cas\hub\mb server 1 and the CAS role on server 1 is having problems, then user 1 can connect to a different CAS server to get to his mailbox, correct? 

    Thats why you want to use a good load balancer, so that can happen seamlessly. If the Client Access Array FQDN is set on the mailbox databases and points to the Load Balancer IP in DNS, it doesnt matter if a CAS fails, the load balancer will take care of routing those client connections to the other CAS in the array.

    Friday, April 27, 2012 6:51 PM
  • Thank you for the feed back. Because they are multi role servers, my thought is that if user 1 is on cas\hub\mb server 1 and the CAS role on server 1 is having problems, then user 1 can connect to a different CAS server to get to his mailbox, correct? 

    Thats why you want to use a good load balancer, so that can happen seamlessly. If the Client Access Array FQDN is set on the mailbox databases and points to the Load Balancer IP in DNS, it doesnt matter if a CAS fails, the load balancer will take care of routing those client connections to the other CAS in the array.

    Correct!

    For the OP - I think looking through this would be a good use of 10 mins. It will cover off multiple things, like the fact that a CAS Array itself provides absolutely no load balancing.  Some form of load balancing is required, be it Windows NLB or 3rd party.

    http://blogs.technet.com/b/exchange/archive/2012/03/23/demystifying-the-cas-array-object-part-1.aspx

    The load balancers that have gone through the validation programme can be found here:

    http://technet.microsoft.com/en-us/exchange/gg176682


    Cheers, Rhoderick NOTICE: My posts are provided “AS IS” without warranty of any kind, either expressed or implied, including but not limited to the implied warranties of merchantability and/or fitness for a particular purpose.

    Tuesday, May 01, 2012 12:28 AM