Implementing RAID

The Redundant Array of Inexpensive Disks, or RAID, is being integrated into more and more new desktop motherboards, bringing greater hard disk performance and reliability to the home user without the need for a third-party device. A RAID setup allows you to install multiple hard drives in your system in various configurations, the two most supported desktop flavours being RAID 0 and RAID 1.

RAID 0

In a RAID 0 configuration, data is striped across more than one hard drive. For example, if you install two 80GB hard drives in a RAID 0 configuration, you will end up with one single drive of 160GB in Windows. This type of configuration will help boost your PC's performance when reading large files, as access and seek times theoretically can be halved due to the fact that both hard drives can be used to read the same file. It is mostly beneficial for applications that rely on fast hard disk performance, such as video editing, which can involve the accessing of many gigabytes of data per file. The downside of this type of configuration is reliability: there is no redundancy of data, so if one of the hard disks in the RAID 0 array dies, then you will almost certainly lose all the data that had been striped over the two drives.

RAID 1

In a RAID 1 configuration, the hard drives will all be replicas of themselves. This means that each disk in your RAID 1 configuration will hold the same data and you will sacrifice total disk space. Following our example above, if you install two 80GB drives in this type of array, instead of getting access to a total of 160GB, as you would with a RAID 0 configuration, you will only get 80GB because the second disk will be used to mirror the first disk's data. This redundant configuration is used to improve data reliability - in the event that one of your drives fails (it can be either one), you will be able to continue using your computer as long as the other hard drive remains intact. Most servers rely on a version of this type of redundant setup, but they will often have hot-swappable drive bays (allowing the replacement of a drive without the need to turn off the server) to ensure maximum uptime of their service.

Case space

One thing you need to ensure when implementing a RAID array is that you have ample space in your case to physically accommodate all the drives you wish to install. A RAID configuration can increase the number of IDE devices that your system can handle up to a total of eight (in conjunction with your regular IDE ports), so a sufficient number of cooling devices will also need to be employed to disperse the heat that your drives will generate. Front and rear case fans are a good investment in this type of scenario, and you will also need to space your drives adequately so that they have breathing room. A hefty power supply is also recommended.

Connections

When installing a RAID configuration, make sure all the drives in your array are correctly jumpered. If you will be using two drives, with one connected to each controller, then both your drives will need to be set up as Master drives. If you will be setting up two drives on the same controller via the same cable, then one will have to be set up as a Master and the other as a Slave. Peruse the markings on your drives or the documentation that came with them to find out which jumpers must be closed.

Once they are correctly jumpered, connecting your drives is very easy. Simply locate the RAID IDE ports on your motherboard, which will generally be a different colour to your standard IDE ports and will be labelled IDE3 and IDE4. Use 40-pin, 80-conductor type cables to attach your drives, placing the coloured end of the cable in the IDE port and connecting the other end to the Master drive.

Defining the array

Most motherboards ship with the popular Promise FastTrak133 Lite RAID controller and this will be the basis for our article. The controller's BIOS can be accessed by hitting a combination of keys during the bootup process, so keep your eyes on the screen to see how yours can be accessed (it is usually -F).

The main screen will give you a menu consisting of about six options. To build an array, you will need to go into the first one, which is the Auto Setup option. From here you can elect to optimise your array for performance (RAID 0) or security (RAID 1). Use the left and right arrow keys to select and press -Y to save your chosen array.

TIP: Some motherboards may require you to go into their BIOS to enable the RAID controller; others may require a jumper setting to be changed. Refer to your motherboard manual for the specifics of your system.

RAID 0

To implement a RAID 0 array, create an array for performance. Save the changes and reboot your computer from your CD-ROM drive or a boot floppy, depending on the operating system you will be installing. Make sure you have the drivers for your RAID controller handy on a floppy disk. If you didn't receive any RAID drivers on a floppy, consult your motherboard manual to find out in which directory on your CD-ROM driver disk they reside, and proceed to copy to a floppy all the directories they advise.

If you will be installing Windows XP or 2000, boot from your CD-ROM and press when the message asking you to hit F6 if you need to install a third party device driver is displayed on the bottom of the setup screen. A little while later you will be asked to specify other storage devices, so press and make sure your RAID drivers are in the floppy drive. Once they are found, you will be able to format the drive and proceed to install Windows as normal.

TIP: If you will be installing a version of Windows 9x on your RAID 0 setup, download the Free FDISK utility from www.23cc.com. Copy it to your boot disk (confirming that you want to replace the existing file) and proceed to partition your drive as you see fit.

When formatting a RAID 0 array for Windows 9x, don't be alarmed if the total space shown is nowhere near what is actually installed in your computer. When Windows is loaded, you will be able to access the full combined space that your RAID 0 array has to offer. Once Windows 9x has installed, though, don't forget to install the RAID controller drivers from your floppy or CD-ROM. Simply go to the Device Manager, double-click your RAID controller entry, go to the Driver tab, click the Update Driver button and specify the location of your driver files.

RAID 1

In a RAID 1 array, where your data will be mirrored, you will have to install your operating system while your primary hard drive is connected to the IDE 1 controller on your motherboard. Make sure that there are no drives connected to the RAID controller yet, and boot via a boot disk or your CD-ROM then proceed to install Windows normally.

Then, from the Device Manager, make sure that you install your RAID controller software. This is a crucial step; if the RAID controller software for your operating system is not installed, you will run into problems when trying to boot the system from your RAID controller.

TIP: If you have two drives of different sizes that will be used in a RAID 1 array, make the smaller one the mirrored (source) disk.

When the driver has been installed and there are no problems, power down your system and attach your prepared hard drive as the Master on IDE 3 and the one that will mirror it as a Master on IDE 4. Boot up your PC, enter the RAID controller's BIOS and proceed to build a mirrored array. When asked if you would like to duplicate a disk image, select yes and proceed to select your source disk (which will be the first on the list). Depending on how big your source drive is, this could take a long while, so consider going for a walk.

TIP: If you run into problems booting from your RAID device, enter your BIOS and make sure that your first boot device is your RAID controller.

If one of your hard drives ever fails, a message will appear upon bootup that will ask whether you want to rebuild the array or continue booting. If you don't have a replacement disk, continue booting to use your computer normally.

When you've sourced and attached a new drive, then the next time you boot up, go into your RAID controller's BIOS and opt to rebuild the array.

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Elias Plastiras

Elias Plastiras

PC World

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