About RAID Technology
RAID (Redundant Array of Independent Disks) is a technology for data storage, which combines multiple Hard Drives into a single logical storage unit. Data is distributed across the Hard Drives according to the RAID configuration (Level), depending on what level of redundancy and/or performance is required.
Basically there are some standard RAID levels/schemes which are well known such as RAID0, RAID1, RAID2, RAID3, RAID4, RAID5, RAID6, but many more variations (combinations of two or more standard levels or non-standard levels) have evolved because of the need of more efficient and reliable storage. Some standard level configurations are shown in the table below:
| Level | Description | Minimum # of HDD | Fault Tolerance |
|---|---|---|---|
| RAID 0 | Block-level striping without parity or mirroring. | 2 | 0 HDD |
| RAID 1 | Mirroring without parity or striping. | 2 | n−1 HDD |
| RAID 2 | Bit-level striping with dedicated Hamming-code parity. | 3 | 1 HDD |
| RAID 3 | Byte-level striping with dedicated parity. | 3 | 1 HDD |
| RAID 4 | Block-level striping with dedicated parity. | 3 | 1 HDD |
| RAID 5 | Block-level striping with distributed parity. | 3 | 1 HDD |
| RAID 6 | Block-level striping with double distributed parity. | 4 | 2 HDDs |
Most common RAID Levels (standard)
RAID Level 50 (combination of RAID 5+0)
