Raid Stands for Redundant Array of Independent Disks.It is 
a set of Technology standards for Teamingup DiskDrives to 
improve Performence and FaultTolerance. Totally there are 6 
levels in Raid
0 - stripping
1 - Mirroring
2 - Stripping and Mirroring
3 - Onfficially Not Defined
4 - Striping with Differential Parity
5 - Striping with Distributional Parity

Raid stands for redundant array of inexpensive disk. there
are two types of raid : software raid and hardware raid.
most of mnc used hdd raid. this is the techonolgy used for
faulttorance and increase perfomance!
there software available raid are raid 0, 1 ,2,3,4,5,6
in which 5 is most used.

redundant array of inexpensive disk, this is used for data
distribution and data redundancy.
levels
0 data distributed (no redundancy)
1 data distributed across disk and having a mirror of each
disk, its expensive
5 data distributed with parity

Raid is Redundant Array of Independent Disks/Device.It is 
Technology to improve Disk read & write Performence and 
FaultTolerance., By adding new disk u can recover data if 
one of disk goes down / fails. parity is a calculated 
technique to rebuild data from disk fails.
levels in Raid
0 - stripping
1 - Mirroring
3 - Striping with Parity
5 - Striping with Parity with more fault tolerant widley 
used.