I have thought of the following configuration with Exchange Server 2010
Main site:
1- two CAS/HUB servers(CAS1 & CAS2) with hardware loadbalancer in a CAS array(CASarray1)
2- two MBX servers(MBX1 and MBX2), all mailboxes divided over 4 mailstores per server, so 8 in total
DR site:
different AD site
1- single CAS hub server (CAS3), in CAS array(CASarray2)
2- one MBX server (MBX3)
I was thinking of to create one DAG over the three mailbox servers. All mailstores are replicated between MBX1 and MBX2, plus ALL mailstores are replicated to MBX3 in the DR site.
Now, when one of the mbx servers in the main site are going down, people can continue working since the DAG provides their data on MBX2 as well. When one of the CAShub servers in the mainsite is going down, I also have a second CAS/HUB.
But now, when both CAS/HUBs and/or both MBX1 and MBX2 are going down, so when the main site is unavailable, how do I switch over to our DR site?
If the MBX server 1 and 2 are down and the user is connected to MBX3, which is in the DR site, it will try to use the CAS3 server there, since it will look for a CAS/HUb server in the same site. And so on....
Could you please advise on how to set up a scenario on this or tell me whether the config I have in mind is correct?
Thanks in advance
Olaf