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Re: The Two Server Distance Problem (Re: DNS Trick??)

To: "LinuxVirtualServer.org users mailing list." <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>
Subject: Re: The Two Server Distance Problem (Re: DNS Trick??)
From: Joseph Mack <mack.joseph@xxxxxxx>
Date: Wed, 30 Apr 2003 10:04:48 -0400
Joel Webb wrote:
> 
> On Wed, 30 Apr 2003, Roberto Nibali wrote:
> 
> Roberto,
> 
> Maybe I am just ingorant with LVS.
> 
> What I need is redundancy between just two computers that is on the
> internet at two different locations.
> 
> I was thinking of doing a cluster with load balancing, but then I would
> have to have a router at one location to balance it which is a failing
> point.

this is not an easy problem. The routing infrastructure has to be
able to find the VIP again when the machine carrying it suddenly appears
on the other side of town. Whether you own the routing infrastructure or your 
ISP owns
it doesn't really matter, but the routing infrastructure has
to have its own redundancy.

> Is there any way to have the load balancers running on both machines that
> the web services are being published??

yes. Have each machine be a director (and realserver) 
and also a realserver for the other machine. Have failover
(Linux-HA or vrrpd) arrange for one machine to be the active
director and the other the backup director.
 
> The only problem that arises with this scenario is if the website is using
> a database. I don't know if the MySQL daemons would be able to handle the
> traffic with the databases not being in close proximity to each other.

actually it's the other way around. You need to know the latency and bandwidth
on the link between the databases to get the performance the customers want.
If they want high availability they have to know that it costs money and they
have to pay for it. 

> And
> all of the database queries that are getting written to them would need to
> be secure as well.

secure connections are standard. They are a bother to set up, but they're
doable.

Joe


-- 
Joseph Mack PhD, Senior Systems Engineer, SAIC contractor 
to the National Environmental Supercomputer Center, 
ph# 919-541-0007, RTP, NC, USA. mailto:mack.joseph@xxxxxxx
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