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Kyle
Asked: 2010-04-02 11:58:51 +0800 CST

How many requests should my apache server be able to take?

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So I just got a nice new VPS service. I was wondering what a good number of 'MaxClients' would be, for a server that will host a personal website, some blogs, etc, and your experiences with one server maxclients stuff! The default of Ubu server is 150.

ubuntu apache-2.2 load-balancing

3 Answers

  1. Best Answer

    How long is a piece of string? :)

    For the most part the limiting factor is going to be memory. Particularly if you are using apache and have a lot of modules installed (mod_php, mod_perl etc); Some of the factors which are going to determine the maximum number of concurrent connections that you can service will include:

    • Amount of RAM in the machine
    • Amount of RAM required to service each http request
    • What else is running on the machine?
    • Nature of the requests and the content being served

    For the most part, 150 is considered a reasonable number. My recommendation would be to leave it as is. If it ain't broke, why try fix it?

    If you do find that your hitting MaxClients consistently then you have a problem which needs addressing.

    I know the answer is a bit vague but there is no real firm figure that can be provided without more knowledge of the environment

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  2. The rough rule is MaxClients = approximate RAM available to Apache ÷ average RAM per Apache process. 150 would probably be way more than your average 256MB VPS slice can handle.

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  3. Assuming it's apache prefork...

    Look at the output of "top" on the system and pay attention to the RSS size of the apache processes. Lets say it's 30M. Then, 512MB RAM / Apache RSS size... suggests a MaxClient setting of around 17.

    If you have over 17 apache processes running your machine will start using swap space for sure... once starting to use swap it can get out of control quickly if it's a busy server.

    However, as it's probably not a busy webserver (you've gone for VPS and it's a personal website) the MaxClient setting is probably on the most part irrelevant as you probably won't be getting many concurrent connections.

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