I have the hub transport, mailbox and cas roles on one server currently. We will be adding 1000 more users to our Exchange environment making a total of 1500 users for this server. I have been thinking about seperating the CAS/HT roles and putting them on their own server to off load the mailbox server load. I know this is a general question but does this seem like an acceptable practice? The opposite side of this is the possibility of providing some redundancy for the CAS/HT roles by using network load balancing and keeping these two roles on the mailbox server but also putting the CAS/HT roles on another server as well to do NLB. Opinions would be appreciated.Alex

Hi,Its better to offload the load on the mailbox server. So you should consider seperating the HUB and CAS role. And yes its good practise to have HUB and CAS role on different server, then the mailbox server.NLB is good option but i would say that you should consider seperating the mailbox server even if you are using NLB.Thanks.

Yes it is a best practise to separate out the Roles. Since the Org is growing i would suggest you to go for separate roles. Exchange will automatically load balance over the two HT roles. The combining of the CAS and the HT has no effect on your use of NLB for the CAS protocols and leaving the HT protocols (25/587)alone. Load Balancing Exchange 2007 Client Access Servers using Windows Network Load-Balancing Technology Part 1: Overview of Windows NLB Clusters http://www.msexchange.org/articles_tutorials/exchange-server-2007/high-availability-recovery/load-balancing-exchange-2007-client-access-servers-windows-network-technology-part1.html Load Balancing Exchange 2007 SP1 Hub Transport Servers using Windows Network Load Balancing Technology (Part 1) http://www.msexchange.org/articles_tutorials/exchange-server-2007/planning-architecture/load-balancing-exchange-2007-sp1-hub-transport-servers-windows-network-load-balancing-technology-part1.html Vinod |CCNA|MCSE 2003 +Messaging|MCTS|ITIL V3|

Hi,To offload the pressure on the mailbox server and keep the high availability, the best practice is separate the CAS/HT and Mailbox server into different server.http://technet.microsoft.com/en-us/library/bb124721.aspxThanksAllen

Thanks for the reply. I have a few more questions. Currently I have one server that has the CAS, HT, and mailbox roles. Would it make sense to keep the HT/CAS roles on the mailbox server, and then run CAS/HT on another server? I can then NLB the new CAS/HT server with the CAS/HT server on the mailbox server. I have heard that you can't load balance the HT role if you have one that is already on the mailbox server role since the HT role that is on the mailbox server will be the prefered path. Also:Does it makes sense at all to NLB(or failover for that matter)the CAS/HT roles when I am not even providing CCR or SCR for the mailbox server.Thanks,Alex

Hi,That is not NLB when the Hub server is installed on the same server as Mailbox. Since it's always the prefered path to route the email via the the local Hub which associated with Mailbox server.Thanks Allen