TABLE 1: RAID Levels and Definitions
RAID Level	RAID Definition
RAID 0 Disk Striping	RAID 0 stripes disk activity across two or more disks. This logical layout provides the advantage of better performance for read, write, random, and sequential environments. The tradeoff is RAID 0 doesn't provide any fault tolerance; if you lose one disk in your array, you lose the data for the entire array. You can increase the number of disks in a RAID 0 environment and improve the random I/O performance.
RAID 1 Disk Mirroring	RAID 1 mirrors disk activity across two or more disks. This logical layout provides for better read performance than one disk (especially in a multiuser environment), but lower performance in a write-intensive environment. RAID 1 provides complete data redundancy, even if you use only two disks. However, this redundancy lowers the capacity of a RAID 1 mirror by 50 percent. For example, if you have two 9GB disks in a RAID 1 mirror, you can use only 9GB of storage space.
RAID 5 Disk Striping	RAID 5 stripes disk data with parity information across three or with Parity more disks. This logical layout provides for better read performance than one disk (especially in a multiuser environment), but significantly lowers performance in a write-intensive environment. This RAID level provides fault tolerance through the use of parity information, allowing for the loss of one RAID 5 member disk without the loss of any data. This redundancy lowers the capacity of a RAID 5 striping with parity by a factor of 1/(number of member disks). For example, if you have three 9GB disks in a RAID 5 array, only 18GB is usable storage space.