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Old 19th October 2010, 09:12
matty matty is offline
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Originally Posted by satimis View Post
Referring to;
The UltraMonkey Solution;

Still I can't understand why it needs 4 servers?

I suppose the 2 "Ultra Monkey (Linux Director+Backup)" represent Real Server 3. What does N on "Real Server N" represent? Whether in this example it is 4. Is it the number of servers on this setup? I can add more than 4 Real Servers?
I think you might be not quite catching on to what is happening in that diagram, and in the original howto. The "real servers" are the application servers, such as webservers, that provide the content. Behind those can be servers that provide data storage and database functions if desired. The Real Server 1, Real Server 2, ... Real Server N means minimum of two real servers, up to any number of real servers. The reason you want a minimum of two real servers is because if you only had one real server, you wouldn't need a load balancer. So, that's two of the servers you need. The other two are for the load balancer (the LinuxDirector in the diagram) and it's Backup in case of failure. The load balancer has the IP address for the application you are serving (say, The real servers have the actual website for The load balancer gets the request from someone browsing the site, and connects it to one of the real servers. The next person that comes along gets connected to the other real server, and so on. This spreads the load amongst however many real servers you have. If the load balancer (LinuxDirector) fails, the standby load balancer (Backup in the diagram) takes over the IP address and things continue with a minimum of interruption.

I need "REAL TIME" redundancy for the load balancer.
If you follow the guides, the loadbalancer will failover automatically in a small amount of time. It would be impossible to have no downtime, as the failure first has to be detected and then acted on, which will take a little time.

But I'm not sure whether the 4 Real Servers need to be identical on packages installed?
It's best if the servers are configured the same way. Two for real servers and two for load balancing. There's no reason you couldn't create a basic VM as a template, clone that out, then configure the servers with whatever packages as necessary.
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