Hello We are in the process to planning a two Datacenter solution with one DAG and 2 MBX Servers. The 2000 users are equaly shared about the two Datacenters and we have one CAS Array in each Datacenter and for the internet we use one entry point Should we work with two namespaces, one for each Datacenter and should we place the witness server in Datacenter one or use a third location for the FSW. Best regards BueschuBueschu

That arrangement will probably not work well for you if you're expecting to use it for high availability. Windows Clustering, upon which the DAG is built, simply doesn't handle geographically distributed clusters very well. You'll likely end up finding that one node or the other will have occasional problems talking to the file share witness or other node and will fail over its databases to the other node, if you're lucky, or will shut down the DAG if you're not. I feel compelled to advise you that if you want high availability, you should have at least two copies of data and the file share witness in each datacenter, and that means two DAGs and six mailbox servers. Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Further to Ed's advise, the design you proposed would work but it will most certainly going to have a WAN vulnerability & in the event of WAN outage, you'll see the service unavailability. I would recommend that you go through the article below http://technet.microsoft.com/en-us/library/dd979781.aspx#Two Since you have one internet facing site, I would rather recommend using Single Namespace but I would suggest you reading the article below also http://technet.microsoft.com/en-us/library/dd351198.aspx Also, in your proposed design model, placing the FSW to third datacenter wont add any resiliency so it wouldn't matter however MS suggests placing in the primary DC & in your case it could be either of the two primaries.

Thank's for the support, which I appreciate. I know the better plan would be to have 2 DAG's with 4 MBX Servers and 2 FWS Shares. The customer doesn't like to have 4 MBX Servers. If we have a fully redudant WAN connection, I think we could risk these scenario (1 DAG 2 MBX active active). Do you agree wtih me? Best regards BueschueBueschu

Yes you can but it is always nice to know pros & cons of any design... Also how ablout using additional(if possible) Mailbox Server that don't contain Databases in a DAG for Additional Votes to your seconday site(DC2) assuming you have placed the FSW to the DC1. See the last part in the first article that i have shared above please. Also I would recommend going through with the high availability misconception please & specifically read no. 2 please. http://blogs.technet.com/b/exchange/archive/2011/05/31/exchange-2010-high-availability-misconceptions-addressed.aspx Regards, Pushkal MishrA

I've read the article about additional voters without a MBX database for a DAG, for example a Hub Server. Does this scenario realy change the rules? I think we get more voters, but what does it help for. Maybe I don't understand this technet article. The key question is, what happens to the DC2 MBX databases if the WAN Link goes down. I think the databases get activated automaticvally on the MBX Server on DC1 - ist this assumption correct? Best Regards BueschuBueschu

Ignore my advice at your peril. My recommendation to you would be the following: If you want high availability, then you want two DAG members in the same datacenter. If you want off-site disaster recovery, then you want at least one DAG member at a remote datacenter, and I strongly recommend running in DAC mode. If you want both, you're looking at three mailbox servers, plus the ancillary servers for other roles. If you want mailboxes homed at both datacenters, you would be looking at six mailbox role servers. Depending on your load and whether or not you have hardware load balancing, you very well may be able to combine CAS and HT roles with your mailbox role servers. As to your question, the answer depends on whether you have DAC mode enabled. With DAC mode, databases are not automatically activated on a mailbox server in a remote AD site, you'll do it manually. You probably want to read up on Datacenter Activation Coordiation mode in TechNet. Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

The key question is, what happens to the DC2 MBX databases if the WAN Link goes down. I think the databases get activated automaticvally on the MBX Server on DC1 - ist this assumption correct? Hi Bueschu, In the event of a WAN outage, the DAG member in the primary datacenter will maintain quorum and continue servicing local users. And I think the databases in DC2 won't be actived automatically on DC1, thus the local users will lose the connections to Exchange server. And after WAN connectivity is restored, it will require manual intervention to restore to service on DC2. But If you have a fully redudant WAN connection, it should be OK. More information, please see: Exchange 2010 High Availability Misconceptions Addressed http://blogs.technet.com/b/exchange/archive/2011/05/31/exchange-2010-high-availability-misconceptions-addressed.aspx Frank Wang Forum Support Please remember to mark the replies as answers if they help and unmark them if they provide no help. If you have feedback for TechNet Subscriber Support, contact tnmff@microsoft.com.

Yes, please do post back in a few months if you choose to deploy cross-site high availability and let us know how it works for you.Ed Crowley MVP "There are seldom good technological solutions to behavioral problems."

Thank's for your help and information Best reards BueschuBueschu