Hints on Running a High-Performance Web Server

Running Apache on a heavily loaded web server, one often encounters problems related to the machine and OS configuration. "Heavy" is relative, of course - but if you are seeing more than a couple hits per second on a sustained basis you should consult the pointers on this page. In general the suggestions involve how to tune your kernel for the heavier TCP load, hardware/software conflicts that arise, etc.

A/UX (Apple's UNIX)

If you are running Apache on A/UX, a page that gives some helpful performance hints (concerning the listen() queue and using virtual hosts) can be found here

BSD-based (BSDI, FreeBSD, etc)

Quick and detailed performance tuning hints for BSD-derived systems.

Digital UNIX


The most common problem on Linux shows up on heavily-loaded systems where the whole server will appear to freeze for a couple of minutes at a time, and then come back to life. This has been traced to a listen() queue overload - certain Linux implementations have a low value set for the incoming connection queue which can cause problems. Please see our Using Apache on Linux page for more info on how to fix this.


Solaris 2.4

The Solaris 2.4 TCP implementation has a few inherent limitations that only became apparent under heavy loads. This has been fixed to some extent in 2.5 (and completely revamped in 2.6), but for now consult the following URL for tips on how to expand the capabilities if you are finding slowdowns and lags are hurting performance.

SunOS 4.x

More information on tuning SOMAXCONN on SunOS can be found at http://www.islandnet.com/~mark/somaxconn.html.

More welcome!

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