Apache capacity

I hear a lot about servers being knocked down because the server can not handle the number of hits.
What does it mean the server is knocked down? Does the computer crash or something? Does Apache have a limit?
How can one find out what the approximate number of hits their server can supply? How does one remedy this problem?

There are a few things that can happen - the main issue is running out of bandwidth. Computers have so much processing power these days, and are so cheap and simple to upgrade, it's not often that you'd run into problems with RAM or CPU speed. Obviously, if you're running a large, dynamic, heavily trafficed site, then the circumstances are different.

Apart from the bandwidth the limiting factors of a web server is the amount of disk access and memory.

If there is a lot disk access the server becomes extremely slow, not a problem with plain web pages because disk access is faster than ethernet. Typically, database requests can generate a very large number of disk access so the organisation/indexing is the way to improve 'capacity' of traffic a server can candle.

If a server runs out of physical memory and has to swap continuely, it behaves as if it has 'hung', having more memory would help but better programming that makes more efficient usage of memory is the issue.

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Sharon White

If you're worried about apache, check out Apache Benchmark, which I think ships with apache and which I know can be executed (if it's installed) at a Linux command prompt by typing "ab" with the appropriate parameters. It allows you to specify a number of connections, a number of hits per connections, and to start hammering the server. And it returns a bunch of data about connection times, dropped connections, etc. Pretty useful stuff.