On 11/4/07, Darryl Miles wrote:
> Usually most setups that need to use a reverse proxy need at least 3
> backend servers.


I think you're missing the purpose of the reverse proxy. Any mod_perl
system will be able to run fewer mod_perl processes if you run a
reverse proxy. It helps with buffering and with the lingering close
problem. There's some discussion here:
http://modperlbook.org/html/12-7-3-B...g-Feature.html

> If you need a reverse proxy then it presumes you have plenty of traffic.


It just presumes you would like to run fewer large mod_perl processes
in total to serve your traffic. It's advisable even with a single
machine to save memory.

> Maybe what you mean is you don't need nearly this many servers if you
> don't have availably targets to meet.


No, I read the original message as saying that the servers were needed
in order to run enough large mod_perl processes to serve the site. A
reverse proxy helps with that by reducing the number of processes
needed.

> A 32bit Linux kernel can access memory > 4Gb (I think this mechanism is
> called PAE and was even a feature of older Pentium 3 CPUs).


I've never seen anyone actually use PAE. It may be because of the
performance hit, or because it requires compiling your own kernel, in
an age where that's no longer very common. Even getting 4GB of RAM to
work in 32-bit Linux was fairly tricky until recently.

There's a summary of information about memory limits in 32-bit Linux here:
http://www.spack.org/wiki/LinuxRamLimits

- Perrin