Exchange 2010 CAS Array and datacenter failover
Posted on 2011-05-09
We have 3 sites in our organization; a remote office, hq and dr. The hq office is connected to the remote office via t1 and to the dr site via 300Mbps link. I am tasked with architecting a redundant Exchange 2010 topology and migrate from our existing Exchange 2003 environment.
I have a mailbox server and a hub transport\CAS at my production and dr sites. At the remote office I have one server that runs all three roles. I want to create a DAG and plan on having copies of my hq database at the dr site and a copy of my remote office databases at my hq site.
My question is with regards to setting up a CAS array. I was thinking of creating a CAS array that has the client access servers in hq and dr. Although these sites are geographically dispersed I was planning on putting them in the same vlan. This way if my CAS in hq goes down clients can still access their mailboxes via the CAS in dr. I'm not sure if the clients in my remote office would default to their local CAS or use the CAS array. I'm also curious as to whether the remote office users will be able to access their OWA via the CAS array.
For external redundancy I was thinking of using a backup URL. Mail.company.com would point to the external IP of the CAS array at prod. Mail2.company.com would point to the external IP of the CAS array at DR. External failover wouldn't be automatic but I don't think it needs to be according to our SLA.
I'm looking for suggestions or reccomendations on to whether or not this design will work.