“I have been reading for last couple of days about designing and deploying Exchange 2010 SP3 based – High Availability and Site Resiliency; in existing infrastructure. Currently we have Single AD Site (Primary Site) – Internet Facing with following Roles.

– 2 Domain Controllers with FSMO roles.

– Single CAS and Hub Transport server (marked as file share witness) on separate box.

– Single DAG (called DAG1) with two Mailbox Servers.

– Edge Transport Server in DMZ.

URLs For OWA/ ECP/ OAB…> WEBMAIL.DOMAIN.COM/*

URLs for Autodiscover > AUTODISCOVER.DOMAIN.COM

Note: we are using single name space and want to keep it as is.

First we want to add more exchange servers in Primary Site to achieve HA as following.

– 2 DCs will remain as is.

– Single DAG with two Mailbox Servers will remain as is.

– will be added another CAS server to make it CAS Array. (how to achieve this? what configuration will it require? can we use WNLB for CAS?)

– will be added another Hub Transport server to make it Highly Available. (Hub Transport Server does not require any configuration for making it HA, is that correct?)

Secondly, we want to add servers in DR Site to achieve Site Resiliency & HA in the event of primary site failure as following.

– Secondary AD site would be created and 2 DCs will be added. New AD site would be called secondary site.

– Two CAS servers will be added as CAS Array in secondary AD site.

– Two Hub Transport server will be added to make it Highly Available and one of Hub Transport will be made alternate File Share Witness.

– Two Mailbox Servers will be added in existing DAG (called DAG1)

– Single Edge Server will be added in DMZ

Question: is this correct order/ approach to introduce exchange servers in existing exchange organization?

We want to achieve following model.

– Users will remain connected/ functional with Primary Site as it is happening in the current scenario >> Users will be routed to DR site only in the event of Site Failure to restore connectivity of exchange users.

– Email flow would be through Primary Site as is but >> will be routed to DR Site only in the event of Site Failure.

– There will be no users connected to secondary site except in DR situation.

– We would want to use single name space as we are currently using (URLs For OWA/ ECP/ OAB…> WEBMAIL.DOMAIN.COM/*, URLs for Autodiscover > AUTODISCOVER.DOMAIN.COM).

– in DR event will be following below mentioned approach per article.

http://msexchangeguru.com/2012/10/25/exchange-2010-dag-dr/

http://msexchangeguru.com/2012/10/30/exchange-2010-dag-dr2/

Questions: Is the entire above stated approach going to work for us? or how can we make it even better?

please assist. Thanks.”