Definition:
- Clone data across multiple disks to have redundancy
- Two different designs manage RAID arrays: hardware and software.
- Hardware RAID uses a dedicated controller attached to the motherboard. This is usually faster, more flexible, and more expensive.
- Software RAID relies on the operating system to manage the storage, which is usually slower, less flexible, and less expensive
- Parity bit:
- Algebrac on other disks to have the equivalent bit → used to find info of 1 disk when its lost
- example: parity of XOR
- disk 1: 1, 0, 1
- disk 2: p, p, p
- parity: 1, 1, 1
- → disk 2: 0, 1, 0
Hardware RAID:
| RAID Level | Minimum Drives | Capacity | Fault Tolerance | Performance | Explain |
|---|---|---|---|---|---|
| RAID 0 (disk stripping) | 2 | Total of all drives | No | High | Striping data across multiple drives. |
| RAID 1 (disk mirroring) | 2 | Capacity of one drive | One drive | Moderate, faster read | Mirroring data across multiple drives. |
| RAID 4 | 3 | Capacity of (n-1) drives | One drive | Moderate | Block-level striping with dedicated parity drive. |
| RAID 5 (disk stripping with parity) | 3 | Capacity of (n-1) drives | One drive | High | Block-level striping with distributed parity across drives. |
| RAID 6 | 4 | Capacity of (n-2) drives | Two drives | Moderate | Block-level striping with double distributed parity across drives. |
| RAID 0+1 | 4 | Capacity of half the drives | One drive in a stripe | High | Mirroring striped disks. |
| RAID 1+0 | 4 | Capacity of half the drives | One drive in a mirror | High | Striping mirrored disks. As same as RAID 1 but 2x amount of disk |