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Intel's Matrix RAID explored

Your array is ready, Mr. Anderson

RAID HAS BECOME an increasingly popular feature on desktop motherboards over the years. The RAID revolution started with high-end boards that integrated third-party PCI RAID controllers, but as chipset manufacturers began integrating RAID capabilities into their core logic, RAID trickled down to more affordable price points. These days, it's hard to buy a motherboard that doesn't support RAID in one form or another.

Despite its popularity as a checkbox feature, RAID has remained a tricky proposition for those with only two drives. A two-drive RAID 0 array may offer better performance, but that comes at the cost of reliability. A two-drive RAID 1 array gives the peace of mind of a mirrored backup drive, but its performance benefits aren't quite as compelling as RAID 0's. RAID levels 10 and 0+1 combine the best of both worlds, but require at least four drives. If only there were a way to balance the benefits of RAID 0 and RAID 1 with only two.

Enter the Matrix. Err, Matrix RAID.

Intel's Matrix RAID technology allows users to combine RAID 0 and 1 arrays with only two drives, promising mirrored redundancy for important data and striped performance for speedy access. That sounds almost too good to be true, doesn't it? Read on to see if Matrix RAID really delivers the best of both worlds.

Matrix RAID: Performance and redundancy from only two drives

What is Matrix RAID?
Before delving into Matrix RAID, we should quickly go over its component parts: RAID 0 and RAID 1. In a two-drive RAID 1 array, data on one drive is replicated to the other in real time. Drives are mirror images of each other, so if one drive fails, no data is lost. RAID 1 arrays can also offer performance benefits since data can be read from both drives at the same time. However, because of the data mirroring, RAID 1 arrays offer only half of the total capacity of the two drives involved.

With a two-drive RAID 0 array, data is broken down into blocks that are striped across the drives. This striping allows RAID 0 to offer superior I/O performance because both read and write tasks are split between the disks. There's no mirroring of data, so the total storage capacity of the array is equal to the capacity of both drives combined. RAID 0's superior performance and capacity come at a price, though. If one drive in a RAID 0 array fails, all data stored on that array is lost. Since the failure of either drive will cause the array to fail, a RAID 0 array's Mean Time Between Failure (MTBF) is half that of a single drive.

To balance performance with redundancy, Matrix RAID allows users to split a pair of disks into two volumes, one for RAID 0 and one for RAID 1. The Matrix RAID scheme mirrors data on the RAID 1 volume of the disk while striping data on the RAID 0 volume. Since Matrix RAID volumes still span two drives, they can offer performance and redundancy benefits similar to traditional RAID arrays.

Matrix RAID's marriage of RAID 0 and 1 may sound a little like RAID 0+1 (or RAID 10), but there are a couple of key differences to note. First, a RAID 0+1 array can sustain a single drive failure without any data loss because its striped data is also mirrored. If a single drive fails in a Matrix RAID array, only data on the RAID 1 volume is preserved—any data on the RAID 0 volume is lost. RAID 0+1's added redundancy does require extra drives, though. You'll need at least four disks to create a RAID 0+1 array.

The vulnerability of Matrix RAID's RAID 0 volume requires care in distributing data to each volume. In a system with Matrix RAID, important data should be stored on the RAID 1 volume, leaving the RAID 0 volume free for data that needs to be faster rather than redundant. For instance, Intel suggests putting the operating system, business applications, and critical data on the RAID 1 portion of the array, while storing games, swap files, and digital media scratch space on the RAID 0 portion.

To Intel's credit, using Matrix RAID is a breeze. RAID volumes are easy to create and configure, and they appear as logical drives in Windows that can be partitioned and formatted as the user sees fit. There is a catch, though. Matrix RAID is currently only available in Intel's ICH6R south bridge. Non-Intel chipsets, including any chipset for the Athlon 64, can't do it.