I have a VPS running a web application served using Apache, that on average deals with 20-50 requests per second. It's usually above this point (50 requests per second) that the amount of memory that Apache uses is too high for the VPS and errors start occuring - web pages crash and VPS falls over for a minute or two before going back to normal levels.
I believe that MaxClients is the best way to reduce the amount of RAM that Apache uses and I am planning to reduce MaxClients from 256 (default value) to around 100. Each Apache process uses ~15MB and the server has 1900MB of ram in total - the server does nothing else other than run Apache and a few crons.
Current setting are:
# prefork MPM
# StartServers: number of server processes to start
# MinSpareServers: minimum number of server processes which are kept spare
# MaxSpareServers: maximum number of server processes which are kept spare
# ServerLimit: maximum value for MaxClients for the lifetime of the server
# MaxClients: maximum number of server processes allowed to start
# MaxRequestsPerChild: maximum number of requests a server process serves
I tried reducing MaxClients before which lead to massive slowness, so I need some other options as well.
Does my suggestion of reducing MaxClients to ~100 seems sensible? What are my options if the server experiences slowness again - optimise the application? What's the best way to reduce memory usage - move images to another web server?
Any suggestions gratefully received!