What is raid?

Basically, RAID began by allowing computer users an increase in storage because they could arrange their cheaper disks into an array, which then could hold more information.  Today, RAID covers any type of system which increases computer data storage.  Today, as software demands on computers continues to grow, there is a need for better retrieval and storage of programming information and data.  This is where RAID systems come into play.

RAID should provide better performance (as the information is being retrieved from more than one disk at a time) and greater reliability (as the information is spread out, so the chances of losing it all is lessened).   RAID technology is either mirrored (same information shared on multiple disks) or striped (information broken into pieces and each disk holding its own piece).  The RAID array is how the disks are connected to one another (usually your computer’s operating system will do this for you, although there are RAID controller software programs available).  Mirroring is more reliable (since you have a complete copy of all the information), but it can also be slower.  Striping is definitely faster (since all the various pieces can be sent at once), but it’s less reliable, since one disk failure will result in the entire set of information not working as it should.

Parity is the solution to the weaknesses in striping and mirroring.  Parity works as an extra disk in the array.  When striping occurs, as each of the other disks takes on a piece of information, complementary information is added to the parity disk.  This way, if one of the other disks should fail, the missing piece can be compared to the parity disk, and then it’s easily discovered exactly what the missing part is so it can be reproduced and added in once again.  Although most RAID technology built into computers are mirrored or striped, for great cost, computer users can also buy RAID parity.