FastCGI over local network

[Igor Clark]

Hi there,

We're building a mainly Flash site which communicates with a PHP  
gateway via AMF over HTTP to get and set database information. The  
app's requests will be something like 50% flat files, and the other  
50% will be PHP. At the beginning of the project we expect a lot of  
SWF requests as we'll be serving rich ads trafficked via some big  
portal sites.

I'm planning an nginx front-end which serves flat content and passes  
PHP requests to a PHP app server(s) on a local network over FastCGI.  
The database will reside on a separate host. The idea is obviously  
that if the app server struggles we can add more, and possibly extra  
nginx servers to help take the load of image/SWF serving if necessary.

In the past, I've only done this with nginx and PHP residing on the  
same host.

Is FastCGI good to do this without introducing problems, or should I  
do something like:

nginx	<--HTTP reverse proxy-->	(nginx+PHP)

Intuitively it seems a bad idea to introduce extra processing, but we  
haven't done multi-box setups with FastCGI this way before, so I  
thought I'd check if that or some other approach might be better.

I'd be grateful for any opinions!
Igor