Concerning the RAID part, it depends what security level you want, many things are possible.
A raid 5 with all 3 disks (safe).
A raid 1 with 2 disks and the last disk makes a daily backup (safe)
A raid 0 with 2 disks and the last disk makes a daily backup (not really safe, but better performance if you have many disk access)
Btw i don't know what kind of website you want to manage but 250 GB for a website is really huge even with a big database and many pictures