Setting up hard drives in a RAID array has become very common lately, with most mid and high-range motherboards including a RAID controller onboard, usually with Serial ATA interface. So it has become easier than ever before. But is it worth the trouble and expense?

Although your motherboard has a RAID controller built-in, a standalone controller card is still a much better option for a serious setup. The onboard RAID on most motherboards gives very average performance, and usually only supports RAID levels 0 and 1, despite the fact they come with eleventy-million SATA connectors, as they don’t have the power to rebuild a more complex RAID array when it goes down, or handle driving it in the first place.

Today we’re going to look at the different versions of RAID most commonly used in desktop PCs and see which one is right for you, if any at all.

What is RAID?

RAID stands for Redundant Array of Inexpensive Devices. And in practise refers to when multiple drives are converted into a single array, either for extra speed, data redundancy or both. When an array is created and being used on a PC, all the drives in the array are only seen as a single ‘virtual’ Hard Drive, so the way that your computer sees and uses the hard drive doesn’t change at all.

The different types of commonly used RAID systems:

RAID 0 – Uses two or more drives, and the controller will ‘stripe’ the data across them. Striping means that the data is spread across all the drives in the array, in the case of a 2-drive array, half the data would be written to each drive, in a 4 drive array, a quarter of the data is written onto each drive etc... This type of array gives no loss of disk space and a big increase in speed. In theory a 2 drive array should give double the speed of a single drive, unfortunately it just doesn’t work this well. You’ll get an average increase of about 25% with a 2 drive array, although certain actions, such as reading large files can bring close to a 100% speed increase.  There is no data redundancy with this setup, so if one drive in the array fails, you will lose all of your data. All of the drive space is usable in this array.

RAID 1 – Uses two drives in a mirrored setup. The same data is written to each drive. This is done solely for data redundancy, if one of the drives in the array fails, the array will continue to function with only the remaining drive, and you won’t lose any of your data. You may see a performance increase when using a RAID 1 array, as the same data is on each drive, they have the ability to be reading in two places at once. This is however controller and operating system dependant, with Windows XP and a basic controller card, you will most likely see a small decrease in performance when compared to a single drive. 50% of your total drive space is lost when using a RAID 1 array.

RAID 10 – A combination of RAID 0 + 1, using a minimum of 4 drives. It is a pair of drives striped for speed, then mirrored onto another pair of drives for data redundancy. In theory performance should be the same as a RAID 0 array, but only if the controller card can handle it. 50% of your drive space is lost with this array.

RAID 5 – Minimum of 3 drives, data is striped across 2 drives with the third drive receiving a parity bit. The drive receiving the parity constantly rotates around the 3. The array can survive a failure of a single drive, but it must be replaced before the array will be functional again. This setup provides an increase in performance slightly less than RAID 0, but is more efficient with your drive space, a 3-drive array is 66% efficient, and the more drives you have in the array, the more space efficient it becomes. This array also allows the use of a ‘hot spare’, a drive that is not used until another drive fails. The controller will automatically rebuild the array using the hot spare and continue to operate, and then when the faulty drive is replaced, it will take on the role of being the hot spare.

JBOD – ‘Just a Bunch Of Drives’ or ‘Drive Spanning’ – Not actually a RAID array, but a common feature of RAID controller cards. It comprises of two or more drives made into a bulk storage array, there are no performance or data redundancy advantages to this setup, but unlike RAID arrays, the drives do not need to be all the same size. Data is written progressively across the drives, once one drive is full it starts writing to the next drive. If one drive fails, only the data on that drive is lost, though it can cause data corruption on the other drives if files and folders were spanned over the working and failed drives. All of the drive space is usable in this array.

There are many more complex RAID array types out there, but these are the most common, and these are the ones we will be performance testing today.

Average user rating