What RAID should I use

Im going to have a server soon and i want to have a nas on it not going to have more then 4 drives, I been trying to figure out what RAID I should use I really dont want to lose anything so i been thinking about raid 6 im only going to use 1gig ethernet so i dont know how much performance loss there would be to using 6 over 5 i dont think i will be getting drives larger then 4 tbs each and thinking of using drive spindown since i really will only use it to back stuff up not to often really just want to know more about if what im planing to do is good and if there is somthing else i should do instead