Setting up a pair of hard disks to work in tandem helps keep your data safe and can improve performance
RAID 0 uses a technique called striping and requires at least two disks. All files that are written to the disk are split up into small chunks that are distributed over the disks in turn.
This reduces the work that each disk has to do and can substantially improve performance. The disadvantage of this system is that all the information is lost if one disk fails, reducing the reliability of the volume as a whole.
If all the disks are the same size, the total of the combined capacity is available for use, for example two 200GB disks would give a total of 400GB. If the disks are not the same size, the size of the array will be determined by using the capacity of the smallest disk as the basis for the total. So if there are two disks, one with 50GB and the other with 100GB, the size of the array would be 100GB (50GB times two).
The second form of RAID, known as mirroring, offers much greater security but at the cost of capacity. Everything written to one disk is automatically written to another.
This means only the capacity of the smallest disk is available but no information is lost if one of the disks fails. There is sometimes a small performance improvement because one disk may find information before the other, but don’t expect to see a radical improvement.
Other forms of RAID
There are many other forms of RAID but most are beyond the scope of home users and based on variations on the two kinds mentioned above. However, we will mention two others that may be available on your computer.
If the RAID controller on the computer is quite advanced, it may offer RAID 5. This is based on striping but adds special information called parity data so that if one of the disks fails, the information on it can be restored. This requires a minimum of three disks, with one being used for the parity data. So if there are three disks of 200GB used in a RAID 5 array, there will be 400GB available for Windows to use.
It is even possible to combine RAID 0 and 1 to have a striped array with each stripe mirrored for security. This requires four disks with the capacity of two available to Windows.
A final kind of RAID does not have a number but is called Just a Bunch of Disks (or JBOD). A number of disks are connected to the RAID controller and appear to Windows as a single disk. The total of the disks capacity is available to use. See JBOD explained, at the end of this article, for more information.
Which to use
Once you have decided to take advantage of RAID, the next step is to decide which form to use. There is no right or wrong answer, but it depends more on what the computer is used for.
Anyone wanting to store family photos, videos or other important information should choose RAID 1 for the extra level of security it offers. Mirroring with RAID 1 provides an automatic back-up, but the material you most value should always be backed up to an external hard disk or a DVD.
Video-editing and games would benefit from RAID 0 and the performance increase it offers. This means less time spent waiting for effects to be applied to video or for game levels to load. Remember that this form of RAID actually increases the chance of losing information from hard disk failure, so keep important data off the array or back up more often.
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