Standard RAID Levels, RAID0, RAID2, RAID3, RAID4, RAID5, RAID6

RAID0 – stripped volume

1. Splits data in two or more disk
2. Has zero parity information, no redundancy or fault tolerance
3. It contributes to improved performance sometimes. – not guaranteed can be lower performance at times
4. Increases logical volume when you have two or more physical volumes

If there are two hard disks a 120GB and 320 GB RAID0 will return 120GBx2 = 240GB

RAID 2

Rarely implemented, involves stripping data at bit rather than block level

It utilizes hamming code for error correction

Offers little advantage over parity, combined with the complexity of hamming code and fact that all the disk need to be in sync as they are controlled by the controller denying it ability to serve simultaneous requests – made it unpopular

RAID 3

Similar to RAID 2 but strips at byte level

RAID 4

Similar to RAID 2 but strips at Block Level

RAID 5

Consist of block level stripping and distributed parity

It can work even if all except one drive were not available

In case of failure of one drive, the reads are calculated from distributed parity to ensure no data loss.

RAID 5 requires at least 3 drives to work.

Has improved performance since all the raid members serve the write requests.

RAID 6

Advancement of RAID 5

It is just like RAID 5 with block level stripping but with double parity block distributed across all disk of the RAID

It can execute Reads and Write request even with two concurrent disk failures.

It has been implemented using several methods including dual check data computation, Reed-Solomon, diagonal parity check data, orthogonal parity check data

RAID6 has great read performance – no penalty

RAID6 has write performance penalty due to parity calculations overheads.

RAID 10

RAID10 basically means RAID1 + RAID0

Combines disk mirroring and disk stripping to protect data.

RAID10 requires a minimum of 4 disks. It strips data across a mirrored pair.

As long as one disk in functional in the pair data can always be retrieved.