Using RAID for Speed and Safety

Don't miss our guide on choosing hard disks.

RAID - or Redundant Array of Independent Disks - comes in different flavours from RAID 0 and RAID 1 to combination of those two, and going up to RAID 5 and RAID 10.

For the purposes of this article we will confine ourselves to RAID 0 and RAID 1. You can use either IDE, Serial ATA or SCSI disks in RAID configurations, but not a mixture of any of them (see our guide to hard disks if you have queries not answered on this page). 

RAID 0

RAID 0 is simply the combination of two or more hard disks to appear to the computer as one large hard disk. It's also called striping. You could take two 250 GB hard disks, set them up as RAID 0 and the PC will see them as a single 500 GB hard disk. Once that is configured and setup for all practical purposes the PC will behave like there is only one 500 GB hard disk in the machine. 

The main advantage of striping is the extra speed that you will get. Writing to hard disks is the bottleneck in most modern PCs. However with RAID 0 the writing is split across two drives, and the PC is writing  simultaneously to both; that does speed things up. You won't get 100% speed increases but 20-30% is quite possible.

The main disadvantage is that there is double the risk of a hard disk failure. You need only one of your two drives to go faulty and you've lost all your data.

RAID 1

RAID 1, also called mirroring, is setting up the two disks such that the second one mirrors the first providing you an up to the minute backup if something ever goes wrong with the first disk. Should the first hard disk fail you simply remove it, put the second disk in it's place and carry on where you left off.  

RAID 0 + 1

You could have a combination of RAID 0 and RAID 1 to provide both the speed and the security. You will, of course, need several hard disks for this.

RAID 1.5

A new concept but the jury is still out on this one. It may give you slightly higher read speeds but write speeds don't benefit.

What you need to setup RAID 0 or RAID 1

You need to have a motherboard that has a RAID controller on it. If the motherboard does not have a RAID controller you will need to add a PCI RAID controller card. Check that the RAID facility it offers covers the type of hard disk you want to use (IDE/SATA/SCSI).

While it is not mandatory to have identical hard disks it is very highly recommended not just that you have similar sized disks but also exactly the same make and model.

Tips:

• RAID 0 + 1 will give you the best of both worlds.
• You do not need to have your operating system on the RAID drives. It is quite possible to have Windows on a 40 GB drive called C and have two 250 GB hard disks setup in RAID 0 as your drive D for video clips
• If going for SCSI RAID note that RAID cards that have dedicated hardware on the card to control the RAID data handling are superior to the software based RAID controller cards.
• When buying a motherboard ensure that it supports not just IDE RAID but Serial ATA RAID as well. When buying a server motherboard you can get SCSI RAID on board.
• Check that your RAID controller has support both for RAID 0 and RAID 1 AND that it has support for RAID 0 + 1; you never know when you may want to add more disks to your RAID. 
• If you want the drive containing Windows to be in a RAID array, setup the RAID prior to installing Windows.
• Don't panic when an IDE or SATA RAID appears as a SCSI device in Windows because that's what it does :-)