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From: Joe Greco <jgreco@brasil.moneng.mei.com>
Message-Id: <199511141700.LAA28800@brasil.moneng.mei.com>
Subject: Re: Multiple http servers - howto ?
To: terry@lambert.org (Terry Lambert)
Date: Tue, 14 Nov 1995 11:00:19 -0600 (CST)
Cc: luigi@labinfo.iet.unipi.it, hackers@FreeBSD.org
In-Reply-To: <199511141527.IAA19839@phaeton.artisoft.com> from "Terry Lambert" at Nov 14, 95 08:27:58 am
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> > I have read that some http servers (probably some machines at NCSA)
> > are actually a cluster of servers attached to the same ethernet. Client
> > transparently contact one of the servers. I would like to know how this
> > is achieved, e.g.
> > 
> >   i) by supplying different IP translations for the same name;
> >  ii) by a clever use of ARP
> > iii) by some other technique which I do not know
> 
> #1.  Via DNS.  The requesting hosts are rotored through a list of the
> addresses.
> 
> It isn't a very good scheme, mostly because caching exists.

Which is why you lower the TTL  :-)  or maybe just not worry about it,
because when you start examining the Bigger Picture, you realize that a site
large enough to require multiple servers is receiving zillions of requests,
and different data will be cached by each domain server, still effectively
spreading the load over multiple servers.

The case where you might lose is if a hundred workstations at the same site
suddenly decide to all run Netscape on a particular URL at once, all hundred
workstations receive the same cached answer from the local domain server,
and they proceed to pound the box into oblivion.  This is the "University
Intro to CS class" problem.  It's worse if they are pounding on your news
server  :-(  which HAS happened to me.

... JG