For that much space i can only see setting up a raid 1 on the two 6GB/s ports as a good back up way is there any down full on read and wright speeds doing this?
also is there any motherbords with more then 2 6GB/s ports?
On Intel you have a max of 2 6Gb/s (not GB/s) ports. But that is irrelevant - for anything but a C300 you won't see any difference, and in fact the ICH10R (SATA 3Gb/s) is faster than any integrated controller anyway, even with SATA 6Gb/s drives.
RAID1 will read and write pretty much like a single drive - so close in performance that you won't notice the difference (very slight decrease in read accesses, slightly longer write accesses, no change in sequential speeds). But RAID1 isn't backup, it is only protection for drive failure. If you get a virus, delete a file by mistake, have your pc stolen, knock over the case, get flooded, etc then RAID offers no protection, but a proper backup stored elsewhere means you can have your system up and running in very little time.