Raid 0, or striping (as opposed to raid 1 mirroring) will make two physical drives into one logical drive. When reading or writing data to the drive, data is split between the two drives. Theoretically there would be double performance because when you are writing say 100 megs to the drive, 50 megs is written onto each. There is some overhead with raid which results in there not really being a true doubling in performance but it does provide significant performance increase over a single drive. I run two 36 gig raptors on my computer and I notice a difference.
The disadvantage is that if either drive goes bad (say a head crash) then you lose the data on both drives. For this reason, I only keep the OS and installed programs on my raid 0 drives. All my data, including my documents and settings folder is kept on another drive.
RAID 0 (Redundant Array of Indenpendent - or Inexpensive - Drives/Disks) is striping data across two or more drives, with no redundancy. RAID is a misnomer for this array, probably should be AID 0, but what can you do?
Your understanding regarding a striped array with two drives is correct: it performs quicker than just using one of those drives.
Cut and pasted from elsewhere:
"Since the data is spread out over multiple disks, the reading and writing operations can take place on multiple disks at once. (My bold and italics). This can speed up hard drive access time significantly. Multiple hard drives may not improve hard disk performace as much as multiple processors may enhance the CPU performance, but it is based on a similar logic."
"I want a redundant array of independent disks striping data across two drives for speed, so don't give me any redundancy!", is what some are asking without knowing it when they ask for RAID 0 on two drives. If you're aware that you're getting zero redundancy when you run RAID 0, then that's good.
When something goes belly-up with RAID 0, the array fails, all is lost.
At the very least, keep another non-RAID drive for backing up files. It is not uncommon to have 2 x 160-320GB drives in RAID 0 with another 250+GB drive as storage. Or if you do have 3 identical drives to start with, go with RAID 5 if you prefer.
I'm assuming you've got a bit of an idea about setting up the array in BIOS and loading the drivers for your operating system when you install it.
One last quick reminder. AID0 only works when you are accessing the drives. For example, it won't boost your FPS while gaming, because the game runs in RAM. Increasing your CPU or GPU (or increasing your ram to a point where it finally runs in ram) will provide a boost. You can run an AID0 setup, but your FPS will still be 45FPS.
It will provide an increase in the level load times, but shouldn't cut the time anywhere near half. Thats because loading a level is more then just reading info from the harddrive. Your CPU needs to uncompress the data, and send info to the GPU. Depending on the size of the maps, you could see only a second or two reduction in time.
If you do anything that causes you to read/write a lot to harddrives, AID0 can pay off bigtime. But as I said, most of us don't need it.