Friday, April 27, 2012 6:10 PM
I'm upgrading from Exchange 2007 to Exchange 2010. I'm planning HA DAG consisting of the primary site having 2 HUB/CAS servers and 2 MB servers and the DR site having 1 HUB/CAS server and 1 MB server. I will have 2 software load balancers (not microsoft) one at each site. I will have a CAS Array setup with DNS pointing to the virtual IP of the load balancer in the primary site and on failover I will change that to point to the virtual IP of the load balancer at the DR site.
My question is with software load balancers are exchange edge servers needed? Do they conflict with the network load balancers? In the current exchange 2007 environment we have an edge server. If I installed edge servers in the above scenario then that will add 2 additional servers one at each site. I'm a little confused on how to implement them with the load balancer and the CAS changes in exchange 2010.
Friday, April 27, 2012 6:29 PM
Edge servers have nothing to do with Client Access servers unless you have them installed on the same box. Internally, Exchange handles the balancing between Mailbox servers and Hub Transport servers. If you have more than one HT and more than one Edge, when you create the edge subscription, the SMTP routing is setup so that all servers can send to each other and if one goes down, it will try the other defined HT or Edge server. From the outside coming in, you technically could use a NLB to balance the ingress from the internet and if your exchange system is directly routing and receiving from the internet, you may want to do this, but you could accomplish a similar function with equal weighted MX records out on the internet.
Currently, I am supporting three CAS, two HT, and four MBX and the only thing the NLB points to are the CAS and HTs, and the only reason the NLBs are pointing to the HTs is to load balance authenticated SMTP connections for users that refuse to move to something other than POP3 or IMAP4.
I guess to answer your question though, it really depends. Do you have any other layers between your Exchange environment and the internet? A AV gateway or some such, like Barracuda spam filter or brightmail? If the answer is no, then you will want to keep the Edge role, if the answer is yes, it depends on how well your perimeter gateway is filtering your mail for you.