I recently down-scaled the server which hosts this blog (one among a few). Being a Ubuntu server, it was trivial to install the LAMP stack, including Apache 2. However, I quickly discovered a problem with the default configuration on a server with a lesser amount of memory (in this case 512MB). The server would work just fine for a short while and then grind to a near halt, where even a SSH session becomes unusable. When I eventually got into the server, I listed the processes and found the ‘apache2’ process running several dozen times!

The default configuration for the Pre-fork MBM (Multi-Processing Module) reads as follows:

# prefork MPM

   StartServers          16
   MinSpareServers       16
   MaxSpareServers       32
   ServerLimit           400
   MaxClients            400
   MaxRequestsPerChild   10000

To something more reasonable to a server with limited memory, such as:

# prefork MPM

   StartServers         4
   MinSpareServers      4
   MaxSpareServers      8
   MaxClients           35
   MaxRequestsPerChild  10000

I found this has made my server much more stable – and I’ve not noticed any performance decrease from the new configuration.