what is raid levels

1) RAID0 - just striping and concatenation

2) RAID1 - mirroring

3) RAID2 - data is striped in all disks where as parity is
stored on different disk. the data is striped at bit level

4) RAID3 - same as RAID2 but the data is striped at byte
level

5) RAID4 - same as RAID2 & RAID3 but the data is striped at
block level

6) RAID5 - the data and parity both are striped at block
level across all the disks.

7) RAID6

8) RAIDZ