Hi everybody, I will be going through the process of implementing 2 x Exchange 2010 Enterprise servers and migrating things over from our Exchange 2003 server. I have a few questions though i would like to ask you all about. Facts of our current setup: - 1 x front end server for OWA - 1 x back end server for the rest - 400 users - 950+ mailboxes - 708 GB mail across 5 MB stores and 15 databases. My questions really relay to OWA, , ECP, CAS ARRAY and DAG. I was thinking to install CAS, HUB and MB on both servers. Both servers will be in our data centre. * If one server goes down, will clients use the other CAS automatically or is a CAS array needed? * I want to use OWA and ECP, but does this needs to be installed and configured on both servers? again i am thinking if one server goes down, let the other one take over. * I think i want to split the active users between the servers on each MB server role and then have copies on each server in case of one of them goes down. Any help is greatly appreciated. Ronnie

Maybe this How to move from a Single Server to High Availability with DAG primer will help from MSExchange.org: http://www.msexchange.org/articles_tutorials/exchange-server-2010/management-administration/how-move-single-server-high-availability-dag.html Also I believe in order to make CAS redundant you need to install and configure the Network Load Balancing Cluster feature of the OS. The CAS and HUB roles use that, where as the Mailbox role uses the Failover Cluster feature. I am not sure if you can run both Cluster types on one box, maybe someone can confirm that for us, but I think you can.

Also I believe in order to make CAS redundant you need to install and configure the Network Load Balancing Cluster feature of the OS. The CAS and HUB roles use that, where as the Mailbox role uses the Failover Cluster feature. Hello, you can't install the NLB feature and the Failover Cluster on the same box. You can use a hardware load balancer instead of the NLB feature (then you can have all roles on the same servers) or separate the Mailbox servers from the CAS/HUB servers. The HUB servers don't use the NLB feature, they are high available after installing them without any further configuration. Greetings, Toni

You can configure CAS Array with DAG on those two servers, but to make it works you should implement Haedware Load Balancing for CAS - e.g. http://www.kemptechnologies.com/us/loadbalancingresource/microsoft-exchange-2010.html Or you can try with DNS round robin (but if one server goes down, your client from time to time would try to connect with nonworking server). OWA and ECP must be on CAS role, so you can't turn it off.Regards, Konrad Sagala, MCT, MCSE+M, MCITP: Exchange 2007/2010

I am still not quite sure how it all works when i have 2 servers in one site. Do i understand this correctly that is i install CAS, HUB and MB on each server, the HUB roles will load balance each other without any further work. With CAS role installed on both servers, would i need a CAS array to load balance the 2? if i dont create a CAS array, then i take it if one server goes down you have to go to the other manually? Also from external access point of view, you would configure your external DNS to look for the CAS array? Do i need a DAG in order to have database copies? I seem to remember that you are able to create a database copy on a different MB server without the need of a DAG Regards R

HT - It's not exacly NLB, but it's true - you don't need to do anything for ha for transport role CAS - you must configure CAS Array and one of 3 possible load balancing option - HLB, NLB or DNS round robin MBX - you need DAGRegards, Konrad Sagala, MCT, MCSE+M, MCITP: Exchange 2007/2010

To sumup, you need both CAS array with NLB (or HLB) and DAG so that if one server goes down, clients can auto-switch to another server. Since DAG cannot setup on a server that is actting as NLB member, you should use HLB if you have only two servers. Or you may consider virtualization such as Hyper-V or Vmware. Refer to: http://technet.microsoft.com/en-us/magazine/ff626260.aspx Fiona Liao TechNet Community Support

To sumup, you need both CAS array with NLB (or HLB) and DAG so that if one server goes down, clients can auto-switch to another server. Since DAG cannot setup on a server that is actting as NLB member, you should use HLB if you have only two servers. Or you may consider virtualization such as Hyper-V or Vmware. Refer to: http://technet.microsoft.com/en-us/magazine/ff626260.aspx Fiona Liao TechNet Community Support Hi Fiona and Konrad, We are actually using VMware with everything sitting on a Fibre Channel San. Both of our new exchange 2010 servers will sit in our datacentre. You say i may should consider virtualization, could you please elaborate on this? have a missed something important in my idea for the design? My initial thinking was to have a much HA as possible so i can make sure that we are covered from a hardware or software failure. Obviously on the VMware side of things we are covered on the hardware side. but i want to make sure that OWA is always up, if a DB becomes corrupt or something that there is a copy of it. Could you comment on my design idea? 2 Exchange 2010 enterprise servers. on VMware with vmotion and disaster recovery enabled. Ronnie

Hi, To make sure that OWA is always up, we need DB high availability and the CAS server with load balancer. To achieve high availability for Client Access and Hub Transport server roles, some form of load balancing should be used between the clients and those server roles. Because these server roles are co-located with a Mailbox server that's a member of a DAG, Windows Network Load Balancing can't be used (because Network Load Balancing and Windows failover clustering can't be installed on the same server). That's why we can not use the existing hardware server to buid both CAS array and DAG. I think the documents below may help ur on the design: Understanding Database Availability Groups http://technet.microsoft.com/en-us/library/dd979799.aspx Database Availability Group Design Examples http://technet.microsoft.com/en-us/library/dd979781.aspx Microsoft Exchange 2010 CAS Array – Steps and Recommendations http://blogs.technet.com/b/omers/archive/2010/10/11/microsoft-exchange-2010-cas-array-steps-and-recommendations.aspx E2K10 + DAG + NLB > need advices for design http://social.technet.microsoft.com/Forums/nl-BE/exchange2010/thread/9a9beedd-3457-4911-9639-8e6c3b3f9415 Fiona Liao TechNet Community Support