RAID
RAID (Redundant Array of Independent Disks) is a way of storing the same data on multiple hard disks or solid-state drives (SSDs) to protect data in the case of a drive failure. There are different RAID levels, however, and not all have the goal of providing redundancy. Let’s discuss some commonly used RAID levels:- RAID 0: Also known as striping, data is split evenly across all the drives in the array.
- RAID 1: Also known as mirroring, at least two drives contains the exact copy of a set of data. If a drive fails, others will still work.
- RAID 5: Striping with parity. Requires the use of at least 3 drives, striping the data across multiple drives like RAID 0, but also has a parity distributed across the drives.
- RAID 6: Striping with double parity. RAID 6 is like RAID 5, but the parity data are written to two drives.
- RAID 10: Combines striping plus mirroring from RAID 0 and RAID 1. It provides security by mirroring all data on secondary drives while using striping across each set of drives to speed up data transfers.
Comparison
Let’s compare all the features of different RAID levels:| Features | RAID 0 | RAID 1 | RAID 5 | RAID 6 | RAID 10 |
|---|---|---|---|---|---|
| Description | Striping | Mirroring | Striping with Parity | Striping with double parity | Striping and Mirroring |
| Minimum Disks | 2 | 2 | 3 | 4 | 4 |
| Read Performance | High | High | High | High | High |
| Write Performance | High | Medium | High | High | Medium |
| Cost | Low | High | Low | Low | High |
| Fault Tolerance | None | Single-drive failure | Single-drive failure | Two-drive failure | Up to one disk failure in each sub-array |
| Capacity Utilization | 100% | 50% | 67%-94% | 50%-80% | 50% |