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Re: LVS with DNS?

To: lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Subject: Re: LVS with DNS?
From: Dan Trainor <dan@xxxxxxxxxxxxxx>
Date: Wed, 28 Sep 2005 19:03:15 -0600
Hello, all -

Sorry to not reply with the correct headers here; I just signed up for
this list, and it just so happened that Jacob Coby asked a question that
was similar to the one which I wanted to ask, so here goes.

What I'm most concerned with here is this.  We are developing a piece of
software in-house which will need to rely on any number of server(s) on
the 'net for some given information.  This system will eventually be
handling financial and transaction data, so complete system integrity is
an absolute must.

Here's what I had rolling around in my head here, hopefully it'll make
things more clear.  Said application will query auth.domain.com.
auth.domain.com first resolves to one of several nameservers listed as
authorative for this domain.  Each of those authorative nameservers are
themselves part of a load balanced cluster, which will then resolve that
auth.domain.com to one of several more load balanced clusters which
actually handle, manipulate, and then return the data to the client
application.  The TTLs for these resolutions would be very very low,
somewhere on the order of 900 seconds.

I really, really don't want to rely on DNS to do my load balancing.  DNS
in itself is a very fragile system, and if I can leave it alone, that'd
be great.  Another reason for this is because I have known DNS servers
in the past to completely ignore TTL wishes, which kindof blows up my
whole solution here.

My ultimate goal is complete redundancy, so that if said client
application cannot eventually contact one of the cluster servers that
handle, manipulate, and then return data to the client, the client would
simply hop to the next cluster, as if nothing happened.   The reason why
I'm taking this approach is because even though DNS resolution may work,
there still may be a broken route between the client and the endpoint
server, which would render the whole situation, well, just plain retarded.

I don't have much experience with load balancing.  From what I've read
about LVS, I'm very impressed.  I am in the process of setting up a lab
to play with it a bit, and from there, I'm sure I'll answer most of my
own questions.  However, I want to stay on the right path, and I'm
hoping that a few of you can enlighten me, since I'm sure that a
situation like this does arise once in a while.

Thanks again for your time.  I greatly appreciate it.
-dant

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