using mongrel cluster

Can someone explain to me what is the purpose o开发者_如何学运维f using a mongrel cluster for a single application? If you have three instances of mongrel running, I assume that you use apache to load balance and the user connects to a single instance. But is there any possible improvements to using it for a single application??

Thank you

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Without a cluster (i.e. just one single mongrel instance), you can only handle one request at a time. So if ten people try to access your site at the same time, they each have to wait. And if one user does something that triggers a long process, no one else will have access to your site until it's done. So clustering/load balancing is always a good idea.

About the only time I wouldn't think it necessary is if you're building a site where there would never be more than one person using it at a time (or if you are totally fine with the potential waits/slow-downs).