[TriLUG] clustering or server mirroring

[David McDowell]

One in the same?  Here's my idea.  I'd like to use CentOS 4 if
possible to do this.  I would like to have my webserver mirrored on
another machine so that if one goes down, the site continues to run. 
If I change a config on one machine, the config should change on the
mirrored machine.  Is this running a cluster or is this some other
kind of setup?  Basically I have some time at work to play.  Any good
resources for this kind of information?  Basically I want 2 servers to
be identical mirrors of one another so that if one of the 2 goes down,
I'm still online.  And, if I repair the broken one, it can resync
itself so that the mirror of the 2 machines is identical again. 
Suggestions, links, etc?

thanks,
David McD