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Date:      Thu, 6 Mar 2003 10:57:42 -0800
From:      "Aaron Burke" <aburke@nullplusone.com>
To:        "Jonas Fornander" <jonas@netwood.net>, <freebsd-questions@freebsd.org>
Subject:   RE: Mirroring/load-balance two servers
Message-ID:  <AMEMKJNMFLJCJDLFIEDBKEDDCKAA.aburke@nullplusone.com>
In-Reply-To: <029001c2e3ac$6133f3f0$0800a8c0@master>

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> Does anyone know if there is a "simple" way to mirror two servers
> without spending $$$$$ on hardware? I'm NOT talking about mirroring the
> OS and the files, I'm talking about sending http requests to a second
> server if the first server is down/un-reachable. This is sometimes
> referred to as load-balancing.
>
> The second server doesn't have to be updated in realtime, it just needs
> to have a fairly current version of the data files of the main server.
> So, for example if the main server goes off line for any reason, then
> web pages would be served up from the second server instead.
>
> Can this be accomplished with DNS?
To my knowlege, yes. Lets say you had a server called www.
You would just give it two addresses in your domain configuration
files.

www	IN	CNAME	12.34.56.78
www	IN	CNAME	9.10.11.12
www	IN	CNAME	65.4.3.21

The DNS standard will give out a different address for every
query. To get the address 12.34.56.78 twice, you would have
to make 4 unique queries for the server records.

One good example of this is to look at www.yahoo.com in nslookup.
	Default Server:  localhost.jupiter.sol
	Address:  127.0.0.1

	> www.yahoo.com
	Server:  localhost.jupiter.sol
	Address:  127.0.0.1

	Non-authoritative answer:
	Name:    www.yahoo.akadns.net
	Addresses:  216.109.125.73, 216.109.125.70, 64.58.76.223, 216.109.125.72
	          216.109.125.67, 216.109.125.65, 216.109.125.66, 64.58.76.227,
64.58.76.228
	          216.109.125.71, 64.58.76.230, 216.109.125.69, 64.58.76.225
	Aliases:  www.yahoo.com


>
> Jonas Fornander - System Administrator
> Netwood Communications, LLC - www.netwood.net
> Find out why we're better - 310-442-1530
>
>
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