Three comments:
1) USB sticks are not reliable as mid-term storage solution, neither are CDs/DVDs. USB sticks should only be used for transferring a copy from one location to another (temporary, short-term storage).
2) A RAID system with main drives is not an alternative to backing up data. Why? See, e.g., http://en.wikipedia.org/wiki/RAID#Data_backup
3) The paragraph about incremental and differential backup is not clear, not to say confusing.