The Dreamhost wiki says you can save memory by disabling mod_php if all PHP-driven sites are already using FastCGI:
"If all domains are set to use FCGI or CGI for the PHP mode, you may safely deactivate mod_php in the PS configuration to save a good deal of memory. All modern PHP applications will run fine exclusively on fcgi."
Is this true?
In the VPS panel it sales the opposite:
"Removes mod_php from the Apache web server. This will save a significant amount of memory if your site serves a lot of static content. PHP-intensive sites may benefit more from setting all domains to use mod_php in Manage Domains and enabling a PHP cache."
I tried disabling mod_php yesterday and my image thumbnail resizer stopped working and gave internal server errors. I'm not exactly sure if this was the reason, or if it was something else going on as we were configuring the server. At the moment, all domains are set to a FastCGI variation of PHP.