storage solutions really depend a lot on how your system is set up, what kind of software you're using, how many people are working with the same files and if you can afford any data loss etc..
all that will make an influence on your best solution so i strongly suggest you'll ask an expert.
++ chris
ps: any sys admin worth his money will tell you that a Raid is not a back up.. its a good protection against down time but more often then notit wont save you from data loss.