Can I have, just a single server dedicated for my needs initially and later on upgrade to a multi server setup
Yes. You can use the Enterprise Edition License initially to run a single standalone server. You can find out what limits you can push a standalone server to, and then even migrate the standalone server to a "Managed Server" with a single click in the Web Console on a need basis. Please note that you can migrate only one standalone server to a "Managed Server". Also the "Load Factor" should help you decide when its time to go for a distributed setup
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