I'm helping some folks who have a CentOS 3 i386 server with 512MB of RAM. The output of 'free' looks like:
$ free total used free shared buffers cached Mem: 511428 497956 13472 0 29868 178280 -/+ buffers/cache: 289808 221620 Swap: 2040244 120644 1919600
The box does not even have X installed... it's basically a web application and email server. They would like to upgrade to CentOS 4, but are concerned that it could be considerably more "memory hungry" and lead to memory starvation (they don't want to add more RAM to the box at this time, although that could be an option down the road).
I ran some tests under VMWare with fresh installations of CentOS 3 and CentOS 4 (both using a "minimal install", the same as the server in question) and CentOS 4 seemed to only use 10-25MB more memory. However, it's hard to know how this will translate into real-world performance over time and with the application installed.
Does anyone have any experience that would suggest how much more memory a non-X server like this might require? If the application(s) on the server stay the same, do you think we would run into issues where memory would be depleted to a level that would cause concern?
Many thanks, KC