Deployment Platform Suggestions?

I’m going to be deploying a rails app in the near future, and am
deciding which web server to go with. It seems like all the cool kids
are using mongrel, which is not a proper web server, behind some other
app. People are also talking about litespeed, and lighttpd was the first
server platform for Rails apps I heard about.

Our site gets around 500,000 reqs/day. We’re planning on a 2-server
cluster behind a hardware load balancer, with a mySQL server and a file
server behind the web servers. The plan is to deploy the app code to the
two webservers, but serve statics such as images/videos from the file
server through a network share on the web servers.

Is there any reason not to use lighttpd in this setup? I’ve benchmarked
both lighttpd and litespeed, and they’re both extremely fast, but I
haven’t delved into setting up Mongrel at all.

I can’t wait to deploy this site. The current site running on Apache
with a Java backend, besides being ugly as sin, runs at about 1.5
reqs/sec. I’ve had to restart apache on several occasions when the
app(whose author has moved on from the company, thank the lord) has
frozen it.

Any suggestions or guidance are welcome.

Thanks
Jason