So, it's no secret (or if it was, it's not any more) that we run Rails to provide the lion's share of our web content. Until recently, we've been pretty much exclusively using nginx + a cluster of mongrels to do this.
As a SysAdmin, I'm required by law to occasionally say, "That won't scale!" (even if it will). However, as someone who really digs the Rails platform, and is constantly hearing all of the FUD about how Rails won't scale, I hate saying that about Rails.
When we needed to mix Rails and PHP on the same server, it posed an interesting problem. But, with a little research, I was able to discover a shiny new gem in the Ruby world - Phusion Passenger.
Passenger got me kind of excited. I'm familiar with Apache, and know it's capabilities. I've run a lot of sites on Apache, and I trust it. And, to be honest, I've felt a little dirty having ditched it the way I have, running around with lighty and nginx behind poor Apache's back. Being able to cleanly use Rails via an Apache module, without a huge amount of configuration hassle, sounded too good to be true.
But, Phusion delivers on that promise with Passenger. Sure, I spent a little time getting up to speed initially, since I didn't want to break any production web apps. But, once you're deployed one site with Apache + Passenger, the rest are a breeze.
And, as far as all that "scalability" stuff goes, Passenger works differently than nginx + mongrel, and in a really good way. I could go on and on about it, but there's a nice write-up here that'll probably do a better job than my blathering.
Add Ruby Enterprise Edition (also from Phusion) to the mix, and you get an extra bit of scalability and performance. REE is an implementation of Ruby which has an enhanced garbage collector, an improved memory allocator, and various developer tools for debugging memory and GC that are not in "standard" Ruby. Combined with Passenger, a Rails app using REE uses a 33% lower memory footprint on average. The performance is also improved on most apps.
See their FAQ for more details.
Now, if only Engine Yard would support Passenger...