Most south bridge integrated
software based RAID capable controllers will support at least the following modes: 0, 1, 5. Sometimes combinations are possibles, but they require an insane amount of drives: 01 (or 0+1), 10 (or 1+0), 50 (or 5+0, some call this 53, 5+3) and they will eat up some of your CPU cycles.
There are other RAID modes out there but you won't find them in the motherboard southbridges just yet.
The Intel ICH/R/DO/DH will support the so called MATRIX RAID mode that is capable of mixing up RAID modes on the same harddrives. For example you can have half of an array as RAID0 for speed and half of the array as RAID1 for a bit of extra security.
I am not a fan of RAID1 because you can only use the capacity of the smallest drive in the array, no matter how many drives you have.
You do need at least 2 of them. It does provide
some performance benefit for reading operation and
some performance hit when writing.
For your data to survive intact, at least one drive must survive intact. The more drives you add, the greater the performance hit you get. Personally I think it sux.
I am using RAID0 in my gaming system, since it doesn't contain sensitive data. In a RAID0 config, you can use the full capacity of the drives if they are of the same capacity (identical drives are recommended for RAID0), or multiply the smallest available capacity with the number of drives to get the usable capacity of the array.
You need at least 2 drives. If one of the drives in your array dies, you data is gone forever... eva... eva... eva... But the speed is great. Both the reading and writing speeds improve when adding another drive to the array. It is not always a linear improvement, but until you reach 4-6 drives you always get a healthy speed bump.
What I prefer to use in my work PC is a RAID5 array. It gives you comparable speeds to the RAID0 array, with the added security of the RAID1 array. But there is a catch.
You need at least 3 drives in the array. For N drives in the array you loose the capacity of 1 of the drives for
parity. The system is very smart, it is not just a specific drive used for parity, but all of the drives in the array, and you can loose one of the drives and your data is still safe. You need to replace the damaged drive as soon as possible, because at this time your array is vulnerable and loosing another drive before the rebuild will cost you all your data. RAID5 is just as speedy as a RAID0.
Now, if you have an Intel chipset, you cand go MATRIX style on your hard drives and setup a RAID0 partition for system data, in order to have speedy performance, and RAID1 the rest of the area in order to have that extra security for your precious, critical, sensitive data. This way you can better manage the space and speed of your array.
I hope this helps.
