Questions Regarding RAID

Ok so I've had some trouble finding useful information on RAID so here's some questions I couldn't find answers to:
- For RAID do all drives have to be the same capacity? (or correspond the same, such as 2x80gb in RAID 0 with one 160gb in RAID 1)
- To set up RAID do all drives have to be formatted?

That's about all that I can think of at the moment
Thanks everyone!

-Nathan

 

1. RAID drives, AFAIK, need to be identical. In other words, same manufacturer and model number.

2. In my experience, they do need to be.

 

A RAID array can't be seen by the OS, the RAID controller makes an array and reports a single drive to the system BIOS. Nothing in the system besides the controller knows it's an array instead of a single disk. And since the filesystem is on a completely different layer the answer is:
No, no format. When you make an array all data on the disks is lost.

Ideally you do want identical disks but you could use different disks as well, the size of the smallest is effectively used. Also, performance won't be optimal.