recommendations on redundancy/fallover methods for IP addresses andDNS names.

Hi,

I have a redundancy issue with an application being written and I am
looking for some recommendations on the simplest ways to achieve a
suitable fall-over for an Internet server.

A quick description.

We have two applications - one running on a portable symbian device and
another on a PC (Windows/Borland).

They both communicate with Linux based Internet servers.

1. The Symbian app connects to Apache/PHP using URL posts to transfer
data into a database via PHP - eg. http://w.x.y.z/insert.php?value=abc

2. The windows app talks to the mysql database via ODBC on port 3306


What we want to use is multiple servers so that if one were to fall
over, the others could continue providing the server facilities to the
apps until it came back. One important fact is that these server
databases do not need to be synchronised in any way, they can be
completely seperate and housed in different locations. All we need is
that both apps can hit one of the servers when required.

For the windows app, it's fairly straightforward. The app could poll the
servers in turn, downloading the appropriate data when it finds it on
any of the machines.

The issue we have is with the Symbian app. With specific requirements of
the app and also distribution. upgrading and configuration of the app to
the phones being more difficult, we would want the app to just try to
access ONE IP address or ONE DNS server name.

So this is the redundancy requirement. We need to use just on IP address
- or alternatively a DNS name - but have it redirect to any of 'x'
number of server depending on what is available. Ideally, these servers
will not be installed at the same location so that there is redundancy
for the network connections to these server-provider locations.

Any thoughts folks?

Thanks,

Steve