Adding an extra server for mail services.

[nonexistentera]

Hello.
I have one server so far for everything, web mail and other things. I am wanting to get another server for load balancing, so that if one server is too overloaded, that it will redirect to the second/third server, finding the one with the lowest load.

Im not to sure how I would do this, but while searching I remember looking over http://www.linuxvirtualserver.org/. Would this be the way to go.

Im a little confused on this, so any help is good.
--nonexistentera

[giggins]

I will try a give a simple sounding answer to a vague question...

I would suggest you setup an additional server, share required data using NFS (mail directories, htdocs, etc), and use Round-Robin DNS (http://en.wikipedia.org/wiki/Round_robin_DNS)to make users utilize both servers.

The link you suggested utilizes virtual servers on a cluster of real servers. Seems like a great concept, but I think Ubuntu 9.04 server already offers something like this through its cloud computing (http://www.ubuntu.com/products/whatisubuntu/serveredition/cloud/uec) stuff. Not really sure which is better, but I've heard good things about Ubuntu's use of Eucalyptus (https://help.ubuntu.com/community/Eucalyptus). Not sure if any of this is really necessary for what you're trying to achieve though.

[nonexistentera]

What one issue I am wondering about is sessions.
What I am trying to do is allow a spread out server layout,
1+ for apache
1 for mysql
... and so on.

So I am wondering how to have the user request sent to the other web server if the others have to high of a load.
I guess what I am trying to do is like what Mininova has.
Like if you visit this page http://www.mininova.org/s it will show like (server-14) and if you refresh the page it will show (server-2).

should I have one main machine to act as a load balancer?

--nonexistentera

[giggins]

DNS is most often cached. This means that using a round-robin DNS configuration will allow sessions to continue working, because once your client machine has looked up the DNS record for www.domain.tld, it will cache it for as long as the TTL is set for.

That said, if you want an actual load balancer for apache, you can use a seperate apache instance, and mod_proxy_balancer (http://httpd.apache.org/docs/2.2/mod/mod_proxy_balancer.html).