Very slow performance on ubuntu/apache2/mysqli when database is on a different server

I'm on Ubuntu where mpm-prefork is the only way Apache can run with PHP (i.e. if I install php5 it automatically installs mpm-prefork even if I wanted worker.)

My problem is that each Drupal page takes a minimum of 5 seconds to load (more than 10 if I request more than one page at once.) An example outline line from the Devel plugin:

Executed 37 queries in 30.5 milliseconds. Queries taking longer than 5 ms and queries executed more than once, are highlighted. Page execution time was 5286.25 ms.

If I start a new mysql console on the web machine, it takes around 5 seconds to login to mysql on the database machine. This didn't seem like a coincidence to me, so with a bit of poking around (ps and netstat) I managed to confirm that a fresh connection to the mysql database was being established for every single request.

I'm using mysqli so using pconnect to try and dodge the problem doesn't appear to be a viable solution (though maybe switching back to mysql is, there is plenty of documentation saying that mysqli is "better".) I have attempted to set up FastCGI, and have in fact succeeded in setting it up but it has not improved the problem. Now what happens is, the php5-cgi processes *do* sit around, but they still connect to mysql every single page hit.

So what I'm looking for is a way around this problem. More than likely this is not Drupal's fault, but something wrong with how Ubuntu's Apache config is managing its child processes.

My mpm-prefork config in apache2.conf looks like this (the default?):

<IfModule prefork.c>
StartServers         5
MinSpareServers      5
MaxSpareServers     10
MaxClients          20
MaxRequestsPerChild  0
</IfModule>

My virtual host config:

<VirtualHost *:443>
    ServerAdmin sysadmin@drupal
    DocumentRoot /var/www/drupal
    ServerName drupal
    ErrorLog /var/log/apache2/drupal_ssl_error_log
    CustomLog /var/log/apache2/drupal_ssl_access_log common

    SSLEngine on
</VirtualHost>

<Directory /var/www/drupal>
    Allow from 192.168.222
    Order allow,deny
    SSLRequireSSL

    # Next three lines added to enable FastCGI - original attempt lacked these.
    AddHandler fcgid-script .php
    Options +ExecCGI
    FCGIWrapper /var/www/cgi-bin/php-wrap .php
</Directory>

The php-wrap script mentioned up there looks like this:

#!/bin/sh
PHP_FCGI_CHILDREN=4
export PHP_FCGI_CHILDREN
PHP_FCGI_MAX_REQUESTS=5000
export PHP_FCGI_MAX_REQUESTS
exec /usr/bin/php5-cgi "$@"

I should add that there is a Ruby on Rails application on the same server using the same database server and that there are no performance issues with that application, which is also using FastCGI.