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From "Christopher D. Harrison" <charri...@doit.wisc.edu>
Subject Re: [users@httpd] multiple apache instances load balancing
Date Tue, 03 Feb 2004 16:40:01 GMT
Pete,
I have a couple of suggestions but have not tested all, listed  
inversely according to risk.

First, (this one I tested, promise) is to set  L4 (redundent) switches  
in front of the two apache instances (I would use two machines).   Have  
the L4 do heath checks on the apache instances and fail one out if it  
does not respond.   Simple L4 redundancy.

The second option I would try is using mod_backhand.   This allows for  
the apache instances to talk to one another, if one apache is down,  
then the other one takes over seamlessly (in theory).   This would  
likely work with an L4, and would be needed if you need to preserve  
apache sessions.   The idea here is to have a hot-spare.

My last option would be to setup two machines that front your tomcat  
and configure them to be clustered.   Therefore, if one machine fails  
the other one could pick up without any outage.   The down side to this  
is complexity and a bit of performance.   Here you need to make sure  
your systems are properly configured so that both machines are tied  
together, but they are not so intrigued such that if one fails, then  
the other does not fail too.   The idea here is to Cluster machines for  
maximum redundancy.

Something to ponder.
	-Chris
On Feb 3, 2004, at 8:48 AM, Pete Stokes wrote:

> Hi.
>
> I've finally got Apache load balancing with Tomcat, but want to  
> provide redundancy to the Apache instance, is there a way to do this  
> so if one goes down the second one takes over seamlessly / works  
> concurrently ?
>
> Thanks,
> Pete.
>
>
>
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