I'm happily using ISPConfig3 with a pool of low-end VMs (2 core XEON and 512 MB RAM). These VMs mainly hosts Wordpress instances and a couple of Drupals. This is why the most applied PHP configuration is FastCGI.
I had many resources issues at the beginning (every 3 days the server was out of memory and killing processes randomly) then I deactivated clamd and amavisd and it got better. Also I tried and configured some options in /etc/httpd/conf.d/fcgid.conf
# This is the Apache server configuration file for providing FastCGI support
# through mod_fcgid
# Documentation is available at
LoadModule fcgid_module modules/mod_fcgid.so
# Use FastCGI to process .fcg .fcgi & .fpl scripts
AddHandler fcgid-script fcg fcgi fpl
# Sane place to put sockets and shared memory file
# Maximum requests a process handles before it is terminated
# Maximum number of PHP processes
But every 2-3 weeks I still have to restart httpd on one VM with 2 Wordpress instances (about 200 unique visitors per day the first one, 10 unique visitors per day the second) as the most visited Wordpress sometimes becomes unreachable (timeout).
I got only this error:
PHP Deprecated: Function eregi() is deprecated in /usr/share/phpmyadmin/libraries/select_lang.lib.php on line 147
and this warning:
mod_fcgid: can't apply process slot for /var/www/php-fcgi-scripts/web23/.php-fcgi-starter
Is there anything else I can do to improve the configuration? Well, maybe I didn't improve it at all with my configuration, but I'd really appreciate some advice.