Hi, this is my first post in this forum, and I would like to take this opportunity to ask anyone who has a dedicated CentOS5 x64 server about how much memory is needed for apache php processes.

Please take a look at the two screenshot with the output of the top command. One if from a CentOS5 x64 Dual Opteron server with 4 GB of RAM, the other is from a CentOS Dual Xeon server with 4 GB of RAM too:

Click to view attachment

Ooops, no more attachemt space for this post, so I will upload the second screenshot in another post.

Anyway, do you see that while apache processes in the Opteron spend around 1.7% MEM. in the Dual Xeon, they just take and average 0.5% MEM.

Of course they are both running the very same software: phpBB2 forums. Why does the x64 Opteron triples the amount of memory the Dual Xeon uses?

Any advise would be much appreciated, especially because it happens that memory for the Opteron is 100% more expensive...

This is the second screenshot:

You look alright. You could probably get away with some optimization before absolutely needing to increase the memory.
Also, keep in mind that Linux is sometimes deceiving when it comes to memory reporting. While it might say you only have about 350MB free, it's usually a bit higher due to the way linux handles the memory allocation to different processes. I can't find my usual reference, however the following URL explains it pretty good.

http://virtualthreads.blogspot.com/2006/02...e-on-linux.html

One thing I'd like to recommend is to add --skip-name-resolve to your MySQLd startup line, especially if there are no outside servers hitting this db. This'll result in a pretty big performance gain since MySQL isn't going to have to do a DNS lookup on every new connection!

There's a million and two optimization guides out there, but if you need any assistance, our Prof Serv guys should be able to help you out.