Building right system for my needs [closed]-Collection of common programming errors

I will be providing “File-Hosting” service and I need something that works with me along the line and allow the project to expand. At first I was thinking about one big server with RAID 5 as a start-up, but then I thought using multiple servers would be better as it’s easier to expand in the future and should be cheaper, but I have absolutely no idea how these servers should/can be linked and if multiple servers would act as a single system.

Can you help me out with ideas and links for information on linking multiple servers together to make them act as one system so I can use all processors & disk space as if it was one server + if one server crashed what are the options available to recover its data? and will the other servers keep working normally?

I still have more questions about geographically different location for servers, and how to pass files from one location to another but it’s not a priority for now.

I’ve read about this feature on Google but they’re using their own file-system and other things that are not available for public.