First, spend some time reading up on RAID levels
Here is a good start;
http://www.pcguide.com/ref/hdd/perf/...evels/tech.htm
For maximum security and uptime, I personally recommend RAID 5 (this is the raid level used at every datacenter I have ever seen) you can make this more robust by going RAID 5+1. Unfortunatly, while RAID 5 can work with as few as 3 drives, for better efficiency, I would recommend 5 drives. 6 if you want to do 5+1
You will also want to go with a high-end dedicated RAID card...preferably something with dedicated onboard cache of at least 256mb or higher. Even better if the card has battery backup...
While the other raids (1+0 will work) I don't recommend it except if redundancy is your only goal.
Ed
web/gadget guru