My company is growing a lot the last couple years. Globally, I have offices in Romania, Spain, Vietnam, China, Singapore plus couple other small offices. We currently have 2 CAS/HUB Servers (VM) and 2 Mailbox Servers in a DAG (physical) installed in the US. In order to improve the performance to our users in different part of the world, I am planning for diversifications. So I am planning to deploy 2 CAS/HUb and 1 Mailbox server to Bucharest, Romania to take care of Europe and 2 CAS/HUB and 1 Mailbox server to Saigon, Vietnam to take care of Asia. My ping rate to Romania is 180ms and to Vietnam is 173ms over Sprint MPLS cloud. Since I have 2 Mailbox servers(in a DAG) in the US, I would like to hold the passive copy of databases of Vietnam and Romania in the existing two US servers. The Mailbox servers in Romania and Vietnam will be holding their own Active Copy of databases. Do I run into site issue with Mailboxes in different locations? If one mailbox server went down, how do the local cas server talk to the mailbox server located in the US? How do I configure the local cas servers for the local users in that country to access their email? I am thinking another domain name in the internet such as romania_cas.mycompany.com and vietnam_cas.mycompany.com. I heard something like affinity can take care of the CAS issue but not sure. If so, anyone can give me an example of how to configure affinity so that I only have to keep one URL for all my users? Thanks.

Hi Do I run into site issue with Mailboxes in different locations? If one mailbox server went down, how do the local cas server talk to the mailbox server located in the US? For configure MBX server High availability you need add MBX servers Romania and Vietnam into DAG from US. When one mailbox server went down, CAS server told clients where active copy database Understanding Active Manager Using a Database Availability Group for Site Resilience Best way use single RpcClientAccessServer value for all databases to configure quick clients reconnect. Designing a Site Resilient Exchange 2010 Solution How do I configure the local cas servers for the local users in that country to access their email? I am thinking another domain name in the internet such as romania_cas.mycompany.com and vietnam_cas.mycompany.com. You can add regional domain for each site. If you want to use Outlook Web App or Outlook Anywhere don`t forget add regional namespase in your SAN cerificate. I heard something like affinity can take care of the CAS issue but not sure. If so, anyone can give me an example of how to configure affinity so that Understanding Load Balancing in Exchange 2010 I only have to keep one URL for all my users? Configure External Client Access Namespaces Thanks.

Thanks Sergey for your answers. Can you clarify what do you mean by "add regional domain for each site"? Can you give an example? I do have site configured in my AD. Yes, I do want to use Outlook Web App and Outlook Anywhere? Do you recommend using differern URL for each site or use One URL for the whole corporation? What are the advantages and disadvantages? Thanks.

Hi I mean plan CAS Namespace first for whole organization include Cas Array name, Internal URL, External URL etc. for each regional site and add those names into SAN certificate Please read links below Robert's Rules of Exchange: Namespace Planning Demystifying the CAS Array Object - Part 1 Demystifying the CAS Array Object - Part 2

Thanks a lot for your direction. Take care!