"RAID can provide several advantages; the degree to which each comes into play depends on the RAID level you implement. These advantages include:

Speed—Writing data to and reading data from multiple physical drives decreases transfer times.
Reliability—Many RAID levels provide data redundancy to varying degrees.
Storage—Combining hard disks can increase overall storage space, although various data redundancy schemes can eat into that bonus.

RAID comes in a number of levels; each represents a different combination of physical drives, fault tolerance, and storage schemes. Current levels of RAID include:

RAID 0
RAID 1
RAID 2
RAID 3
RAID 4
RAID 5
RAID 6
RAID 7
RAID 10
RAID 53
RAID 0+1"