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From Guy Hulbert <>
Subject Re: load balancer "cluster" set
Date Mon, 31 Jul 2006 17:56:35 GMT
On Mon, 2006-31-07 at 19:34 +0200, Graham Leggett wrote:
> Users of mod_backhand (for httpd v1.3) would disagree, it's a similar


Asks the right question:

	How are load balancers actually built?

and suggests: zeus, mod_backhand, and router solutions but unfortunately
does not give a direct answer.

However, two paragraphs down:

        Failover from a broken load balancer to a working one is
        essentially a network configuration challenge, beyond the scope
        of this textbook. Basically what is required are two identical
        load balancers and cooperation with the next routing link in the
        chain that connects your server farm to the public Internet.
        Those upstream routers must know how to route requests for the
        same IP address to one or the other load balancer depending upon
        which is up and running. What keeps this from becoming an
        endless spiral of load balancing is that the upstream routers
        aren't actually looking into the TCP packets to find the GET
        request. They're doing the much simpler job of IP routing.

This points up the difficulty of trying to solve the problem at the
application level.

My point was that free routing solutions to this problem were already
available since 1997.

> solution that has been around for years. The lb support in v2.x will

The mod_backhand site seems to date since 2000 and Greenspun's article
is dated 2003, which also seems to be the latest release of
mod_backhand  ...

> hopefully eventually allow users of mod_backhand to migrate to v2.x
> from
> v1.3.

... it certainly seems to be important to create the migration path but
you have yet to convince me that the scalability is the same.

However, you have certainly convinced me to try the apache solution once
it is available ... I have a customer who might need it in a year or so.


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