Performance & Scalability Considerations

I am designing a small load balanced system of web servers which will each be running a single web application that is database search intensive. My initial thoughts are to have single multiprocessor machine with a large striped raid array handling the data mining and several less expensive front end boxes serving the requests (and static data) in a load balanced configuration.

Am I correct in assuming that since a networked high performance share would be handling the intensive file i/o that the cpu's in the front end servers would benefit from noticeably lower loads? Or would the difference be offset by network traffic overhead?

Furthermore, how much of a performance loss will I take reading from a network share raid as opposed to a local one of the same configuration?

For example, lets assume a dual processor machine and a hardware raid stripe w/out partity reading from multiple SATA 3.0 drives? Assuming a GB(1000) nic/switch, at what point does the speed of the network transfer limit the transfer from the raid and diminish the speed gained by reading from the stripes?