Web Hosting Talk : Web Hosting Main Forums : Dedicated Server : CPU load low, server slow, need more ram?

[Tertsi]

Hey,

My server gets 300 - 600 concurrent connections to http port 80, has a CPU load of 1 - 2%, has practically all RAM of 1 GB used, is running apache 2 and centos 5.

It tends to get slow and when I ban IPs that use many connections to my server (raping it), it becomes fast again. But soon after that new ******* users come which I again ban and the process repeats itself

I'm starting to think that maybe I just don't have enough RAM to handle them because it seems at least some of those users are legit. I don't however have even that much content that needs to be cached so I'm not sure what good RAM would do but perhaps apache just needs more.

So what should I do?

[cristibighea]

You need to optimize your Apache; RAM on Linux will appear all used because of how it works, but are you using a lot of swap?

[Tertsi]

Practically no swap is being used. I have looked at optimizing apache but just don't seem to find anything to optimize. Care to help me get started on that? My cpu is pentium D 3.0 ghz or so.

[Tertsi]

For example now it has been fast since that server raping ended for 20+ minutes.. But why is it so easy to rape the server, making it very slow? Seems like 11 concurrent connections will do it in some cases? Are successful dos attacks from a single IP address possible with such a low amount of connections?

[AcuNett]

If you are not swapping at all, it is unlikely you are utilizing all of your free RAM. What is the output of free -m?

[Tertsi]

My errorlog says that I reached the MaxClients limit.. so I now increased it to 512 along with the ServerLimit setting and it seems I only get these problems during the evenings so we'll see how it goes this evening.

[Xandrios]

Well if you increase your MaxClients limit more connections will be allowed, and thus more loaad will be generated.

Is the problem that your server load becomes too high, or that browsing your website(s) is slow? In the last case it could be that indeed you were just maxing out MaxClients, and that things seemed slow due to the 'waiting' for a client connection.

Another thing you can try is turning off keep-alive. That will free connections directly, and not keep them open. Thus less waiting time when the MaxClients limit is reached.

[Tertsi]

browsing my website becomes slow.. CPU usage remains at 1 - 2 % or so, certainly not near 100 % and swap isn't really used either, ever. Thanks for that keepalive tip, I wonder how big I can set that MaxClients setting? (How much do you guess my server that serves APC cached php pages could handle?)

[joelin]

Originally Posted by Tertsi

My errorlog says that I reached the MaxClients limit.. so I now increased it to 512 along with the ServerLimit setting and it seems I only get these problems during the evenings so we'll see how it goes this evening.

Hi,can i ask where do you get the errorlog file about MaxClients limit?


thanks

[w00ts!te]

It depends whether you run the standard installation or a customized control panel installation.

[agnivo007]

Huge concurrent connections and still 1GB RAM usage...something fishy! Avg. apache process is ~15MB AFAIK.

Probably your're maxing out maxclients and banning IPs produce more checks for every connection and low performance. Try increasing RAM and tune your maxclients, timeout etc. Enable keepalive to 1sec.