Raid Levels

Provides improved performance, but no redundancy.
Data is written in blocks across the entire array.
Disadvantage: Low reliability

Provides 100% redundancy, and good performance.
Two matched sets of disks contain the same data.
Disadvantage: Cost

Consists of a set of data drives, and a set of Hamming code drives.
Hamming code drives provide error correction for the data drives.
Disadvantage: Poor performance and relatively high cost

Stripes bits across a set of data drives and provides a separate disk for parity.
Parity is the XOR of the data bits.
Not suitable for commercial applications, but is good for personal systems

Like adding parity disks to RAID Level 0.
Data is written in blocks across the data disks, and a parity block is written to the redundant drive.
Would be feasible if all record blocks were the same size.

RAID Level 4 with distributed parity.
With distributed parity, some accesses can be serviced concurrently, giving good performance and high reliability.
Used in many commercial systems

Carries two levels of error protection over striped data: Reed-Solomon and parity.
It can tolerate the loss of two disks.
Write-intensive, but highly fault-tolerant

Employs pairs of over-lapping parity blocks that provide linearly independent parity functions.
Can tolerate the loss of two disks.
The use of simple parity functions provides RAID DP with better performance than RAID 6.
Somewhat degraded performance from RAID 5.