Adding extra hard drives doesn't just increase your storage; it also speeds your PC and helps you recover from hard-drive failure. Drives configured as RAID deliver more than the sum of their parts.
Every RAID level balances performance and fault tolerance differently.
RAID 0: This level spreads--or stripes--data across two or more drives, which speeds data transfers. If you frequently move lots of data on and off drives, you'll notice a performance boost from a RAID 0 array; but if you mainly do standard PC tasks, you won't realize much speed gain. Backing up is critical, since RAID 0 doubles your chances of losing your data: If one drive fails, you lose the data on both drives.
RAID 1: Unlike RAID 0, RAID 1 provides no improvement in performance. Instead, this level offers bulletproof fault tolerance by generating an exact copy, or mirror, of your hard drive in real time. If either drive goes belly up, you can just use the other one until you have replaced the failed drive and rebuilt your mirrored copy. RAID 1 does not free you from the need to back up, however: Any data corruption, viral infection, or accidental deletion will affect both drives identically.
RAID 1+S (mirrored sparing): Certain RAID controllers support this technology for installing a third hard drive that lies dormant until the boot drive fails. At that point it automatically replaces the failed drive, repairing the array and protecting the data without your having to lift a finger. The downside of both RAID 1 and RAID 1+S, of course, is that you can't use the mirror drive to store data.
RAID 0+1 (aka 01) and RAID 1+0 (or 10): The former mirrors striped drives (creating a mirrored backup of data that has been placed on several different drives to improve reliability), and the latter stripes mirrored drives (moves mirrored backups onto several drives to improve performance). Both configurations require at least four hard drives. RAID 0+1 stores data on a pair of striped drives and mirrors them with a second pair of drives. RAID 1+0 places the mirrored pairs together and then stripes the two sets.
RAID 5: This level also provides striping and data protection, but it safeguards data far more efficiently than RAID 1. Instead of mirroring one drive with another, RAID 5 stripes data and parity information across three or more drives. The parity information helps to recover a failed drive, using data on the surviving drives. The downside: You need at least three hard drives for each array, and RAID 5 controllers cost more than their counterparts for other RAID levels. However, the RAID controllers built into many motherboards today--even some fairly low-cost models--support RAID 5.
Planning Your RAID
Installing a raid setup requires two or more hard drives and (if you don't already have one) an open SATA or IDE connector for each drive, which most new motherboards have integrated. Many high-end PCs sold in the last couple of years support RAID 0 and RAID 1, and some handle RAID 5. If yours doesn't, you can add RAID and SATA or IDE channels to any PC by installing a RAID adapter from a vendor such as Promise Technology, Highpoint Technologies, or Adaptec. A RAID 0+1 adapter that supports two hard drives costs less than $75, and a RAID 5 adapter for up to four drives is available at under $150.
Here are few RAID tips:
- If there's no room in your PC's case for additional drives, buy a RAID adapter with external SATA connectors, and place the drives in an external housing such as Addonics' $75 Saturn ExDrive.
- Windows XP Professional and Windows 2000 can act as a software RAID controller for striped RAID 0 configurations, but not for mirrored RAID 1 or RAID 5 setups. Though this may save the cost of a hardware controller, the Windows solution is slower, and Windows itself can't be installed on either striped volume. Browse to Microsoft's support page for more.
- Follow the hardware vendor's installation instructions carefully, and always back up before installing RAID devices; installation problems can destroy the drive's data. Check the vendor's Web site for driver updates and additional installation information before you start.
- If your RAID configuration uses parallel ATA drives, set each drive as a "master" on its own IDE channel to ensure peak performance.
- When installing Windows on a striped RAID 0 or RAID 5 array, you need a floppy drive to load your RAID drivers. For some reason, Windows looks for RAID drivers only on the A: drive.