Describe the different RAID levels.  Discuss the choices of the different RAID levels for different applications.        

 Ans:   There are several combinations of these approaches giving different types of trade offs of protection against data loss, capacity, and speed. RAID levels 0, 1, and 5 are the most generally found, and cover most needs.

1. RAID 0 (striped disks) distributes data across various disks in a way that gives enhanced speed and full capacity, although all data on all disks will be lost if any one disk fails. 

2. RAID 1 (mirrored disks) could be explained as a backup solution, by using two (possibly more) disks that each store the same data so that data is not lost so long as one disk survives. Total capacity of the array is just only the capacity of a single disk. The failure of the one drive, in the event of a software or hardware malfunction, does not raise the chance of a failure nor decrease the reliability of the remaining drives (second, third, etc).

3. RAID 2 It employs memory style redundancy by using Hamming codes, which consist of parity bits for distinct overlapping subsets of components.

4. RAID 3 It employs a single parity disk relying on the disk controller to figure out that disk has failed.

5. RAID 4 It employes block-level data striping.

6. RAID 5 (striped disks with parity) combines three or more disks in a way which protects data against loss of any one disk; the storage capacity of the array is decreased by one disk. 

7. RAID 6 (less common) can recover from the loss of two disks by P + Q redundancy scheme by using Reed- Adoman codes.