RAID Implementation

Originally, RAID systems were available only with SCSI hard disks, which are quite expensive. In the past few years, companies like HighPoint (http://www.highpoint-tech.com), Promise (http://www.promise.com), SiliconImage (http://www.siliconimage.com) and ITE (http://www.ite.com.tw) released a series of RAID chips enabling RAID systems together with IDE hard disks, the most popular kind of hard disk around.

These chips can be found on add-on cards or on the motherboard itself. So, even if your motherboard doesn't have RAID function, you can simply install an add-on card to enhance your system speed and reliability. Some chipsets have RAID function embedded on them, as it occurs with the lastest chipset from Intel (for example, on the Intel 915P, but the south bridge must be ICH6R or ICH6RW to have this feature available) and VIA (VT8237 southbridge).

On Figure 1 you can see a real example of a motherboard with on-board RAID feature. It has four regular IDE ports, two controlled by the chipset (no RAID function as it occurs with the vast majority of motherboards available at the market) and two controlled by an extra chip from ITE called GigaRAID IT8212F, and also two Serial ATA ports controlled by SiliconImage SiI3112 chip. These two ports controlled by GigaRAID chip have RAID0, RAID1 and RAID0+1 functions. So if you want to use any of these functions, your hard disks must be installed to these ports. You can also not use the RAID funtions at all and use these extra ports just as regular IDE ports.

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Figure 1: Detail of the extra IDE ports from Gigabyte GA-SINXP1394 motherboard.

We gave all our examples using regular IDE hard disks, but RAID is available for Serial ATA devices as well. In the example of Figure 1, the Serial Ports available on this motherboard doesn't allow RAID function as SiliconImage's chip does not support it. But there are Serial ATA chips around that supports it.

Another option is RAID thru software. Instead of a special RAID chip controlling the hard disks, it is possible to enable a RAID system using a special RAID software. The advantage is that it is cheaper to use software-based RAID solutions. On the other hand, it is less reliable than hardware-based RAID solutions.

Below you will find a table with the most common RAID chips that come with motherboards that implement on-board RAID function.

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