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Once reserved for servers and high-end workstations, RAID technology for linking multiple hard drives is gaining favor with PC users looking to improve performance affordably. Tests by PC World show they're on to something: Two RAID-connected drives completed some tasks in 40 percent less time than one drive of the same type.

RAID (Redundant Array of Independent Disks) technology comes in many flavors, but two are finding desktop popularity, thanks in part to low-priced add-in PCI cards and to some system vendors (such as Alienware, Falcon Northwest, and Polywell) that offer PCs with the technology. RAID Level 1, or mirroring, writes all data to two drives at once, ensuring the information survives if one drive fails. More popular with performance buffs is RAID Level 0, or striping, which interleaves data between two drives to create a double-size drive with about twice the effective throughput.

Numbers Up

To measure the real-world performance boost striping provides, the PC World Test Center tested pairs of 7200-rpm IDE ATA hard drives from three vendors. Each drive had 80GB of storage and a 2MB cache; all were tested with Promise Technology's $109 (list) FastTrak TX2000 ATA RAID card. (With standard RAID cards, you must use same-size drives.) Expect Serial ATA RAID cards when more Serial ATA drives hit the market in early to mid-2003.

We tested each solo drive using the IDE adapter on the test PC's motherboard; then we linked each pair of matching drives to the Promise card and ran the tests again. In our Copy Files and Folders test, Maxtor's $149 (list) DiamondMax Plus 9 finished first, with 118 seconds (solo) and 80 seconds (striped drives)--about 32 percent less time. Seagate's $105 (street) Barracuda ATA V drive was slower than the Maxtor, but completed the test in 42 percent less time with RAID than it did solo, dropping from 174 to 101 seconds.

Western Digital's $129 (list) Caviar WD800BB drive was tops in our Copy Large Files test, completing it in 83 seconds solo and in 76 seconds striped, or about 8 percent less time. Again the Seagate improved most dramatically with RAID, plunging from 151 seconds to 84 seconds--about 44 percent speedier.

Despite also boosting scores slightly in the Photoshop and Quicken tests, RAID didn't get top marks in all our measures. In most cases, our file-find and Corel Photo Paint tests took more time with RAID, though typically by a scarcely perceptible 5 percent or less.

RAID doesn't offer across-the-board benefits, but it improves performance significantly, particularly on slower drives and for disk-access-heavy functions. So if you get a second drive, consider buying a RAID card, too. And if speed is a priority in your next PC, see RAID-friendly vendors like those mentioned above, or mainstream vendors such as Gateway in coming months.