Re: Conceptual questions...

[Chris <cditri@xxxxxxxxxxxx>]

Thank you Joe,

Things are becoming clearer for me.  I guess what screwed me up in the 
first place is when I looked at the diagram on Ultramonkey for a highly 
available load-balancing service.  I this schema there are two load 
balancers.  That got me questioning:  'What balances the load blancers?'
How do you do this?  What associates the VIP with the appropriate 
machine?  Do the load balancers balance themselves, or do they need to be 
balanced from above?
For example the address I want the world to point their browsers to is 
63.232.103.54 (fictitious).  That machine is my iptables firewall 
machine.  My firewall would Dnat to the directors' VIP, then the director 
would send it to one of two real servers serving the website.
Can I have my load balancers balance themselves?  Does Piranha do this?  Or 
do I need something else?  It seems to me that the VIP can only be 
sponsored, so to speak, by *one* machine (based upon what I have been 
reading).  I know that can't be right though!  Can the balancers balance 
themselves and share a VIP without having it sponsored by another machine 
"above" it?
This would really help me get my head on straight!

Thanks again!

chris




At 01:22 PM 1/11/2002 -0500, you wrote:
> On Fri, 11 Jan 2002, Chris wrote:
>
> > Q:  is the VIP an actual IP address configured on an actual interface (or
> > alias for an interface) that resides on the load-balancer?
>
> yes
>
> >       So traffic routed to that VIP would then be subject to some 
> balancing
> > algorythm or another (performed by the load balancer), and sent to (via
> > dnat or tunnel etc) a real ip address of a real machine serving a real 
> service?
> yes
>
> > If this is
> > the case then the VIP is really a real IP, right?
>
> yes
>
> > I had thought, that the
> > VIP was a floating address between two or more machines, meaning that
> > machine A and machine B can share 10.10.10.10 (for example), and then took
> > turns, so to speak, taking responsibility for that address.  I am now
> > thinking that this is not the case.
>
> if you have 2 boxes to act as directors, to guard against director
> failure, then only one of them can be the director at a time and only
> one can have the VIP. In this case, the software that is controlling the
> failover will have to move the VIP from one of these boxes to the other.
>
> Joe
>
> --
> Joseph Mack, mack@xxxxxxxxxxxx
> Linux Virtual Server project
> http://www.linuxvirtualserver.org
>
>
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