What is RAID?

RAID is an acronym that stands for "Redundant Array of Inexpensive (or Independent) Disks." RAID stores data on more than one drive to make sure nothing gets lost. It also allows recovery of data from failed disk drives without shutting the system down.

There are many different levels of RAID, each having their own specific method of protecting the data stored on each hard drive.

RAID 0:
Uses data striping, simplest RAID level, involves no redundancy

• Increases the speed of the reading and writing process
• Best to have drives of the same size when using striping
• By giving up redundancy, this RAID level has no loss of disk space.

RAID 1:
Uses mirroring or disk shadowing

• Requires a minimum of two drives that are exactly the same size
• Mirroring - when a drive has its data duplicated on two different drives using either a hardware RAID controller or software
• If one drive fails, the other continues to function as a single drive until the failed drive is replaced.
• Lose half of your disk capacity

RAID 5:
Accomplishes both techniques of RAID 0 and RAID 1

• Requires a minimum of 3 drives
• The more drives on the server, the better RAID 5 will perform
• More expensive; price ranges from $1000 to $5000 depending on the total number of drives, type of drives and controller required

• Loss of disk space is 100 divided by number of drives (i.e. 5 drives, 20% loss of disk space)