[buug] hardware load balancing vs software

Michael Paoli mp at rawbw.com
Wed Sep 1 22:53:24 PDT 2004

Well, actually, BIND (generally) hands out all the IPs each time, but 
round-robins the order each time it hands out the IPs.

Generally speaking if the client doesn't get a response from the first of
multiple IPs, it eventually times out and goes on to subsequent IPs, until
it gets one that responds, or exhausts trying the various IPs.

Note however if the server does "respond" - such as with connection
refused (server being brought up or down, or server up but service down),
the client doesn't bother trying other IPs.

So, in short, BIND DNS round-robin can do some crude "load balancing"
of sorts, and it may be adequate for some scenarios, but in many situations,
at least by itself, it may not be sufficient.

Quoting johnd <john at jjdev.com>:

> our system (hardware and software) knows not to send traffic to boxes
> that our down

> if I did this and a server went down, bind would still give the ip
> out and teh client would get a error

> On Tue, Aug 31, 2004 at 07:40:15PM -0500, Neal Samarakkody wrote:
> > John de la Garza wrote:
> > >I'm not asking if we should use tomcat or apache

> > >Im asking if we should use a hardware loadbalancer or apache to load 
> > >balance

> > >apache will be used regardless

> > the easiest way to do load balancing between webservers is to have dns 
> > do the work.  having the same name like www point to different ip's will 
> > cause dns to cycle through the list of ip's for a certain name as 
> > requests arrive.  actually, this is the manner in which bind behaves.  i 
> > am assuming most other dns daemons behave similarly.

> > so you do not need a hardware load balancer or apache to do load
> balancing.

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