Hi All, We going have 2 Data Centers and have a requirement to host 50% of mailbox in each (basically a Active / Active setup). Using Exchange 2010. Most users will be using OWA so I will be setting up an CAS Array in each Data Center and Hardware Load Balance them. This will mean I will have 2 Hardware Load Balanced Virtual IP's (one for each CAS array). What I then want to do is give all my users a single name space to login to OWA e.g. webmail.domain.com rather than telling each user depending on which Data Centre their mailbox is located in to use either CAS-Array1.domain.com in data center 1 or CAS2-Array2.domain.com in data center 2 ... (which is not practical when you have thousands of users and also in the case of a Data Center Outage). What is the best way of doing this? Setup another Hardware Load Balancer to load balance CAS-Array1.domain.com and CAS2-Array2.domain.com. Then have webmail.domain.com set to this new Virtual IP? Then the users have a 50/50 chance of hitting the correct CAS Array 1st time? e.g. if a user is directed to CAS-Array1 in Data center 1 but their mailbox resides in Data Center 2, then the CAS-Array1 will proxy the user accross CAS-Array2? Is this correct and the best way to host 50% of users in each Data Center? P.S Some users will be using Outlook 2007 / 2010 and I presume the autodiscover should sort them out? Thanks ECL

Hi I think you can configure in setup Virtual IP two IP CAS array adresses for your Enviroment. HLB can understand where all CAS array and detect where stored user`s database If Data Center one will be shutdown, you must edit Hardware Load Balancer Virtual IP on the CAS array in Data Center two. http://technet.microsoft.com/en-us/library/dd638104.aspx - Namespace Planning Also you must use San Certificate, or Wildcard Certificate for configuring all certificate names.

Thanks for the link it is useful. The requiremnet I have is both data centers must be Active (i.e. Data center 2 is not a standby and both Data Centers will host 50% of users and on any site failure 50% of the users will failover to the other site). I spoke to the network team and they said it will be better if I provide the users with separate Data Center 1 and data center 2 name space. Otherwise when I use the HLB it could hit either data center 1 or 2 and cause lot of un-nescessary traffic if it hits the wrong CAS Array. e.g. if using HLB a user is directed to CAS-Array1 in Data center 1 but their mailbox resides in Data Center 2, then the CAS-Array1 will have to redirect / proxy the user accross CAS-Array2 to find the correct mailbox. Basically I don't want the users transversing between the data centers too much in order to find their mailbox and not have to use multiple name space to keep things simple. I think I will need to do some testing :) Thanks

"if used HLB a user is directed to CAS-Array1 in Data center 1 but their mailbox resides in Data Center 2, then the CAS-Array1 will have to redirect / proxy the user accross CAS-Array2 to find the correct mailbox" Yes you`re right. Remember, CAS Array settings it`s object mailbox database. Every Mailbox Database have property "RpcClientAccessServer=FQDN of YourCAS Array" CasArray maybe only one per site.

Thanks for your input Sergey Regarding Outlook 2007 / 2010 clients I presume the autodiscover would automatically redirect users to the correct CAS Array even in the event of a Site failure? As for OWA users I am thinking of creating a vbs script that determine the users mailbox location on the users desktop e.g. by checking property of homeMDB. Then when they run the OWA icon (script) on the desktop it will either access cas-array1.domain.com or cas-array2.domain.com depending on which site the users mailbox resides in. And in the event of a Site failure it will access the working one only ...