Cisco Application :: GSS 4492R Configuration With ACE4710?

I have to deploy the Cisco GSS in our 2 dataceters globally seprate IP ranges to loadbalance the exchange 2010 environment with Cisco ACE 4710 series SLBs.  The scenario is to deploy  one GSS + ACE on each datacenters and our nameserver will point to both GSS's IP addresses to get through. Incase primary site "site A" goes down name server will point the client's request to "site B".
 
What will be the physical setup of the GSS here and what configuration should on SLB ACE will make it work? Do GSS and ACE need to be in the same vlan? is this necessary to use Both interface of the GSS to get things working?  How the GSS will check the health check on ACE if they both are on different vlans/ip range? Our ACE will be in routed mode do we need to assign the Real server default gateway as ACE inside interface with the server farm or just do the SNAT of the client IPs so the request can come back to ACE?