If you are building a PC you might decide to install two or more hard drives. If you link these drives in a RAID setup you can speed up your computers performance and even provide automatic protection against data loss from hard drive failure.
If you do decide to set up a RAID configuration, make sure you have an adequate power supply (PSU). Some RAID Adapters have been known to take more than the normal amount of power to function adequately.
There are many different RAID combinations involving just a few or many hard drives. What follows are three particularly useful RAID combinations that are ideal for businesses, gamers and experienced home users.
1. A RAID 0 setup increases hard-drive performance by spreading (or striping) data over two drives so that it can be read and written more quickly. Unfortunately, such an array provides no data protection. In fact, it actually increases the 
chances of data loss since the failure of any one drive results in the total loss of all the data stored on both hard drives.
RAID 0 setups are standard on high-end gaming and graphics PCs, and provide a measurable, although modest, performance boost for games, graphics applications, and other hard-disk-intensive programs.
2. A RAID 1 setup protects data from a hard drive failure by simultaneously writing data to two hard drives - a master drive and a backup (or mirror) drive. Since the second drive carries an exact copy of the first, it provides no usable storage capacity. RAID 1 offers no gain in drive performance.
3. By opting for RAID 5 you get both faster hard drive performance and full data protection. This set up requires a minimum of three hard drives.
Instead of using an entire hard drive as a backup, RAID 5 spreads redundancy information - called parity bits - across all of the array's hard drives, increasing the proportion of usable disk space. A three-drive RAID 5 setup provides two drives' worth of storage capacity, a four-drive array offers three drives for storage, and so on as extra drives are added to the array. If one of the hard drives fails, the data content of that drive can be recalculated from the redundancy information on the surviving drives and written to a new, replacement drive.
You probably already have a RAID adapter in your PC as many midrange and high-end motherboards come with a built-in RAID controller. Check your PC or motherboard documentation to find out if your motherboard supports RAID (and if so, which levels it supports), and consult any specific installation instructions.
If your PC doesn't have RAID support built in, you'll need an RAID Adapter Card. Adapters supporting RAID levels 0, 1 and sometimes 5 can be found online. Adaptec, Belkin and Promise offer a wide selection of RAID adapters.
In theory, most RAID 0 setups can be configured with hard drives of different sizes from different manufacturers. In practice, you'll save yourself a lot of time and grief by building your array with identical hard drives - meaning drives of the same make, model, and size.
If you plan to install Windows XP on your new array, you will need a floppy disk with your RAID adapter's Windows drivers, and a floppy drive to read it. A Windows' XP installation will not install the drivers from an optical drive. Thankfully, this is not a problem with Windows Vista or Windows 7 or 8, as you can use a CD to install the necessary drivers.
Here's how to install a RAID adapter card in your PC.
Unplug your PC and position the case so that you can comfortably reach into the interior. If you have a tower case, you'll find installing an expansion card easier if you lay the case on its side.
Protect your PC's delicate circuits from static electricity charges on your body by properly grounding yourself. If you don't have the patience or time to buy a grounding strap, at least make an effort to ground your body by touching your PC's case before touching the inside of your PC or any component.
Locate an open PCI or PCI Express expansion slot and remove the cover bracket that blocks the slot's access port on the back of the case. Typically, a single screw secures the bracket.
Remove the adapter card from its packaging and carefully align the card's connector with the expansion slot and gently but firmly push down on the top edge with even pressure until the card is securely seated in the slot. Now secure the card to the chassis with the existing screw or other clamping mechanism.
Once the card is installed, install and connect the multiple hard drives to be used in the array. See "Hard Drive Replacement and Addition" for help with drive installation.
Now reassemble the PC and start it up.
Each RAID adapter has a firmware configuration program, unique to that make or model, that lets the user select the type of RAID array to install and choose which hard drives to include in the array. Refer to your adapter or motherboard documentation to guide you thorough the specific installation steps for your adapter.
Typically, you launch the program by pressing Ctrl-R, Ctrl-A, or some other key combination during the PC boot process. Watch the screen for a prompt and check your adapter's documentation. (You may have to configure your SATA hard drives for use in a RAID configuration)
When asked to select a stripe size or chunk size for a RAID 0, RAID 1 or RAID 5 array, select the default size. Playing with these settings may increase performance for users with plenty of time and energy to experiment.
If you are installing Windows XP:
Carefully watch the bottom of the screen at the very beginning of the setup process for the prompt, and press F6 if you need to install a third-party SCSI or RAID driver. Be quick: You have only a few seconds to press F6 and launch the installation process.
Wait for the screen that says 'S=Specify Additional Devices' in the lower-left corner. Press S.
When prompted, insert the floppy disk with the adapter's drivers into the floppy drive and complete the driver installation.
Once that is done, Windows should continue the Windows installation routine.
Once it boots into the Windows desktop you can begin to install all your programs.
No extra steps are needed. Enjoy your new RAID set up.
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