This is a huge topic, but I'll give you the reader's digest version.
RAID (Redundant Array of Inexpensive Disks) is a data storage method used to increase data rendundancy and/or access speed, essentially it allows you to access data more quickly, and/or implement data redundancy (backup). Here's a quick overview of popular schemes:
RAID 0 (Striping): One file is stored half on one disk, half on the second, so that both disks can be accessed simultaneously during read. Most desktop users wont see the performance increase from this. (All RAID schemes are mostly found in a server environment)
RAID 1 (Mirrored): One file is stored in its entirety on both disks, this way if one disk fails, you still have a working copy of the file on the other disk.
RAID 5: RAID 5 combines both aspects of RAID 1 and RAID 0 with striping and mirroring, via parity data (RAID 5 requires a minimum of 3 disks, and the usable storage space is equal to (n-1)*s, where n is the number of disks, s is the smallest disk in the array.) There's plenty of sites that really describe the details of all these schemes. So I wont recreate the wheel here, just google it.
JBOD is a term that's often thrown in with RAID. Just a Bunch Of Disks (JBOD) essentially creates one large drive consisting of many smaller drives. As with all RAID schemes this is transparent to the user.
Like I mentioned earlier, most people won't notice the benifit of RAID (Especially RAID 0) in a desktop environment. These were all developed as server technologies, to increase data security (redundancy) and access time (striping).
Hmmm...yeah, a google search would have been better than creating a thread asking what RAID is...but out of sympathy, here's a pretty good article explaining RAID and another also explaning RAID and it's uses. I recommend given them a read and then creating a thread to fill-in the blanks.
RAID (Redundant Array of Inexpensive Disks) is a data storage method used to increase data rendundancy and/or access speed, essentially it allows you to access data more quickly, and/or implement data redundancy (backup).
To my knowledge it does not increase access speed in itself, it allows to increase total bandwidth so larger file can be transfered more quickly. The access speed is determined mostly by the rotational speed of the disk (7200 RPM vs 10K RPM vs 15K RPM). Correct me if I'm wrong.
Unless you REALLY know what you want, I suggest ONLY the RAID 5 or NO RAID.
One large drive is more reliable than RAID 0 and RAID 5/ 6 has most of the reliability of RAID 1 with good performance (at the expence of using 3+ drives).
RAID 0 can be faster in some benchmarks.
What I personally do is have one C: small/fast (Raptor) drive at the system drive with the OS and all applications stored (all applications loaded from CDs). Then one large D: drive for all data/media/etc. Then if windows has a serious crash, all your data is safe on the larger drive.
Pros, please don't yell at my answers, I am just trying to make thing simple.
But here is one small but serious problem. Im a gamer, is a nice idea to have a Raptor as the main (windows) hard drive so windows will be faster. And the second one bigger so you can store data,media,movies,music etc.
Here is the problem, if any gamer like me wants to have the fastest game possible, you would have to install for example Doom 3 in the raptor. Thinking you have a 36Gb or even 74Gb Raptor, by 2 or 3 months you will see you dont have enough space remaining. Thats a little disavantage of the famous Raptor. the 150Gb still might run out of space in a short period of time. But I dont wanna imagine how much would cost the 300Gb version!!!