Hi, I have two sites running exchange 2003, and would like to extend this to a third site. My question is what is the best way for me to setup redundancy in this scenario using exchange 2007?The redundancy should include the fastest and easiest way to restore any failure in the chain (ofcourse), and each site will be active.Should I implement CCR at each site? Is there anything clever I can do here? Can I use SCR between sites?How should I build in redundancy for the edge,client,access and unified messaging servers?Thanks,

For other roles than mailbox you build redundancy with multiple servers. With mailbox role you can use CCR or SCC. CCR can be stretched out to physical localtions, but its limited to 2 nodes per cluster. This takes carefull planning though and isnot the intended way of using CCR even though its possible. SCC can also be stretched out geographically, but you must also stretch your storage at the same time. both CCR and SCC is automatic failover. with SCR there is not and the intention is to havea fast recovery site. http://technet.microsoft.com/en-us/library/aa998636(EXCHG.80).aspx

I roughly understand how CR works, but I have a problem seeing how to implement it across three sites.What is the configuration you would recommend?From what I understand the most redundant config would be to run CCR/SCC locally at each site, therefore not relying on the link in between sites. Is this possible? What would be the mailflow here?As all of my sites are "live" I guess I do not have a case for running SCR then?

what you can do is to have a CCR cluster in each site, this would give you 2 server in each site with automatic failover within the site. You can add servers in other sites acting as SCR targets, this would give you manuall failover if something bad happens in the SCR source site. ex. 2 servers with CCR and acting as SCR source, and then two servers acting as SCR targets from other sites this gives you 4 mailbox servers in each site, then you must also add CAS and HUB servers in each site. depending on your server load you may have to scale up with multiple servers this is just a simple suggestion and must be investigated carefully

Thanks for your reply. I was also thinking along those lines.Can you have multiple edge servers at two different sites for site resilience? If so can I have multiple edge servers at each site for redundancy?Can I NLB CAS and Hub servers for redundancy between sites? If not would I need to provide multiple CAS,HUB, AND UM servers at each site?

You can have one edge subscribed toi site A and another edge subscribed to site B. you can also have multiple Edge at each site. NLB cannot be used between AD-sites,NLB must use the same subnet. HUB is also "tied" to its own site, so you need multlple CAS and multiple HUB in each site for redundancy.