As I have a few moments I thought I would share some of my experiences of running PHP as a Fast CGI script as oppossed to an Apache module. Some of you might be wondering why would I want to do that? Well....
I have been leasing and maintaining various Plesk based webservers for a while now (more info at www.loboweb.eu) and have noticed that in some circumstances, Apache memory usuage and subsequently the server memory overhead can be seriously reduced by switching running PHP from a Apache module to as a FastCGI script, as oppossed to the default of running as a Apache module. This can have the overall result of making the server more robust and less likely to use swap memory etc. The difference can be quite noticable if you are using Watchdog to monitor your memory usuage.
Enabling PHP as a FastCGI script is made fairly straightforward in Plesk for a while now. Simply select 'FastCGI support (required for Ruby on Rails) ' and ' PHP support run as Fast CGI Applicaton from your general Hosting Settings Account Control Panel.
However there were a few more things that may not be so clear so I thought I would share them with you here:
Enabling PHP as a FastCGI Script also creates a seprate php.ini in your /var/vhost/www/mydomain.com_folder/etc
So where as before you may have used the apache conf vhost.conf file in your /var/vhost/www/mydomain.com_folder/conf folder to say by adding 'php_admin_flag allow_url_fopen on' now you have to go to /var/vhost/www/mydomain.com_folder/etc/php.ini to make your adjustments.
More info here: http://kb.parallels.com/111697