RAID configurations
by Kyluke McDougall on 19 January 20151 min readWhat does it all mean, when do I use what?
What Is RAID?
RAID stands for redundant array of inexpensive disks; or now more commonly redundant array of independent disks.
The idea of RAID is to use multiple disk in conjunction with each other to create 1 logical Volume. For example, you would use RAID to couple together 4x1TB hard drives to create what looks like 1 4TB hard drive. Each RAID configuration has it's own purpose and will be used for completely different applications.
For instance, RAID 1 would be used for backup purposes and redundancy while RAID 5 would be used to create larger logical volumes out of many smaller hard drives.
Have a look at the table below. It breaks down each configuration by it's name and description.
| Level | Description | Minimum Drives | Fault tolerance | Read perf. | Write perf. |
|---|---|---|---|---|---|
| RAID 0 | Block-level striping without parity or mirroring | 2 | 0 (none) | n× | n× |
| RAID 1 | Mirroring without parity or striping | 2 | n-1 drives | n× | 1× |
| RAID 2 | Bit-level striping with dedicated Hamming-code parity | 3 | One drive | (Varies) | (Varies) |
| RAID 3 | Byte-level striping with dedicated parity | 3 | One drive | (n-1) | (n-1) |
| RAID 4 | Block-level striping with dedicated parity | 3 | One drive | (n-1) | (n-1) |
| RAID 5 | Block-level striping with distributed parity | 3 | One drive | n | (n-1) |
| RAID 6 | Block-level striping with double distributed parity | 4 | Two drives | n | (n-2) |
| RAID 1+0 | Mirroring without parity, and block-level striping | 4 | One or more drives per span | (n/spans) |