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The competitors
ATI, Intel, NVIDIA, SiS, ULi, and VIA core logic chipsets all feature various flavors of RAID, but the only widely available options that offer support up to four drives and RAID 5 are Intel's ICH7R south bridge and NVIDIA's nForce4 family. ULi's new M1575 south bridge does support up to four-drive RAID 5, but it's only just becoming available on a small handful of ATI CrossFire motherboards—products that weren't available when we began our mammoth testing spree several months ago. VIA's VT8251 south bridge will also support four-drive RAID 5, but that chip currently exists only on reference boards, and even then without complete drivers.


Intel's ICH7R south bridge

When Intel revealed the ICH7R in May of this year, the south bridge was the first core-logic chipset component to support RAID 5. The ICH7R also supports RAID 0, 1, and 10, but arrays are limited to up to four Serial ATA drives. Those Serial ATA drives will enjoy support for Native Command Queuing (NCQ) and 300MB/s host transfer rates, though. The ICH7R also includes an interesting feature called Matrix RAID, which allows users to create RAID 0 and RAID 1 volumes spanning just two drives. We've looked at Matrix RAID's performance extensively in the past, so we won't be covering it today.


NVIDIA's nForce4 MCP SLI

Our second competitor is NVIDIA's nForce4 SLI MCP, the south bridge component of nForce4 SLI Intel Edition chipset. Like the ICH7R, the nForce4 chip supports RAID 0, 1, and 5. However, NVIDIA has elected to support RAID 0+1 instead of RAID 10. (We'd obviously prefer RAID 10 for its greater fault tolerance.)

While the ICH7R's RAID support is limited to Serial ATA drives, the nForce4 also supports RAID with plain old ATA drives. This capability allows the south bridge to handle arrays with up to eight drives (four ATA and four Serial ATA), although support for NCQ and 300MB/s host transfer rates will obviously be limited to the Serial ATA drives.

NVIDIA first made RAID 5 support available in its core logic chipsets with the nForce4 SLI Intel Edition, but the same RAID controller is used across the nForce4 Ultra, SLI, SLI Intel Edition, and SLI X16 chipsets. Only the latter two currently offer RAID 5, but according to NVIDIA, that capability can be added to the nForce4 Ultra and SLI chipsets with a motherboard BIOS update.

While we're on the subject of chipsets, it should be noted that there's a significant gap in interconnect bandwidth between the Intel and NVIDIA chipsets. The nForce4 SLI Intel Edition's interconnect between the north bridge and south bridge chips tops out at only 1.6GB/s, while the Intel chipset enjoys 2GB/s of bandwidth. 400MB/s isn't chump change, but our benchmark results should provide more insight on whether the discrepancy in interconnect bandwidth makes much of a difference.

Software RAID with Windows XP
Every time we do a RAID performance comparison, I get emails asking why we haven't included Windows's software RAID. Windows 2000, XP, and several flavors of Windows Server are capable of creating software RAID volumes, regardless of a system's chipset, using dynamic disks. However, several limitations keep us from directly comparing OS-level software RAID with chipset implementations. First, some array levels, such as RAID 5, are only available in server versions of Microsoft's operating systems. Support for these levels can be hacked into Windows XP with a hex editor, but they're not officially sanctioned. We wouldn't recommend relying on an OS hack to provide redundant storage. The creation of a Windows software RAID array also requires that the operating system already be installed, which prevents users from creating a striped system volume. That limitation doesn't exist for any of our chipset RAID implementations, which can easily be implemented for system drives.

1.6TB of Caviar
RAID arrays should be configured with identical drives for best results, and we've rounded up a quartet of Western Digital Caviar RE2 hard drives for this comparison. The Caviar RE2 is an enterprise drive that's apparently optimized for RAID environments, and its impressive single-drive performance has already earned it a TR Editor's Choice award. The RE2 also weighs in at 400GB, allowing us to configure RAID 0 and 5 arrays with over 1TB of total capacity. Sorry Paris, that's hot.


Four Western Digital Caviar RE2 400GB hard drives