Cisco Security :: Mini Data Center Design For 6500

I have some doubts about the best solution for the design of a mini data center.In the data center there is a 6500 with FWSM module installed, there are some vlans created, all of them in the fwsm module. For example, a back end server to communicate with a server in the front end must always pass through the firewall. My question is, all these flows passing in the firewall does not degrade the speed of communication?What is the best practice, just pass the communications with the WAN in the firewall, and the vlan communication between front end and back end is only set up in 6500?