I have already selected httperf as the load testing tool to use. I'm trying to figure out some realistic parameters to use, and if I need to use multiple machines to create more simultaneous connections, etc. I've done some basic load testing before but nothing very sophisticated.
The only information I have about the estimated load is that I'd like to be able to handle 3 million hits in a day. Part of my problem is that I don't have a good rule of thumb for how web traffic is "bursty". Clearly, it depends on the specific site and is never the same twice. But, maybe there is a rule of thumb that says, if your average load for a day is X requests per second, then you should plan for Y simultaneous connections and a peak rate of Z requests per second.
I've done a fair bit of searching around, and while I've found a number of explanations of the various load testing tools and their parameters, I've never seen a decent write up of how you can come up with realistic values to use for the parameters.