[Sunhelp] DNS Roundrobin?

[Kalusniak, Jeff]

Thanks Dale!  You've given me the reassurance I was looking for.

This will be strictly a test environment to evaluate the performance gains
of a cacheing engine that we are lloking at.  It will be a controlled test
(by me) and will be for about 1 week.  So, it sounds as of the DNS
round-robin may be the best method.  Our web brokers distribute the load to
our app servers with horrible balance as it is, so this can't hurt that much
:)

And, I would never consider incorporating this into any long-term
architecture.  As I said, it's solely for testing and solely for one week.

-----Original Message-----
From: Dale Ghent [mailto:daleg at elemental.org]
Sent: Friday, October 20, 2000 4:00 PM
To: 'sunhelp at sunhelp.org'
Subject: Re: [Sunhelp] DNS Roundrobin?


On Fri, 20 Oct 2000, Kalusniak, Jeff wrote:

| We are trying to balance web requests to 8 different servers for testing.
| Ideally, we'd put a LoadDirector or BigIP unit in front of it. However, we
| cannot get this accomplished in the time-frame required.  
| 
| Does anyone know what the best solution would be to accomplish this with
| softeare?  Perhaps some DNS round-robin?

Well, DNS round-robin would certainly be the quickest and easiest
implementation for load sharing. The only problem with it is that it does
not guarantee that you'll get anywhere near equal distribution of
connections among your 8 servers. As a stopgap measure, I'd use it, but I
wouldnt want it to be a part of my site archetecture for long. You're at
the whims of web clients and other name servers regarding which of your
servers gets hit, and plus, if one server goes down, you'll have to take
it's IP out of the rotation and hope that not many people try to hit it as
it expires out there in DNS land (so this means, keep your zone's TTL
down. Side effect: your DNS server gets hit much more)

There's a perl-based named front-end out there called lbnamed (there's a
link to it off of isc.org's BIND page I think) that tries to make the load
spread more even and controlled, but in my experience it's kludgy at best,
and I wouldnt want to put it in a place where DNS lookup times are
important.

The next step up from doing it DNS-style, and with out using something
like a Alteon or LocalDirector, is to get a box running the ipfilter
package. You can configure this to do stateful transparent redirection to
your cluster of 8 servers. I've worked with this in the past and it was
pretty good at doing that.

Hurrah for L3/4 switches.

/dale

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