What is RAID?
RAID stands for "Redundant Array of Independent Disks". Discover the different RAID types and how they work. SOS Data Recovery recovers your RAID data with a free 3-hour diagnosis.
How does RAID work?
The history of RAID dates back to 1987 when the term RAID was introduced in an article published by the University of Berkeley.
The word RAID is actually an acronym for "Redundant Array of Independent Disks," which can be translated to French as "Regroupement redondant de disques indépendants."
Implementing a RAID system allows achieving several essential objectives:
SOS Data Recovery, a Swiss laboratory based in Ins, has been recovering data from all RAID systems since 2006. Over 11,300 media processed for more than 8,000 clients. Free diagnosis within 3 hours. CyberSafe certified.
Software RAID or hardware RAID?
A RAID system can be managed in two ways:
Software RAID — managed by the operating system (Windows, Linux, macOS). The machine's processor handles parity calculations and data distribution. Cost-effective solution but CPU-intensive with lower performance.
Hardware RAID — managed by a dedicated RAID controller (PCIe card or onboard controller). The controller has its own processor and cache memory with backup battery (BBU). Optimal performance and independence from the operating system.
In the event of a failure, the recovery method differs depending on the RAID type (software or hardware) and the controller used. SOS Data Recovery works with both types with the same free 3-hour diagnosis.
RAID level comparison
Redundancy, fault tolerance and performance — each RAID level has its own characteristics.
| Type | Principle | Min. drives | Redundancy | Fault tolerance | Performance |
|---|---|---|---|---|---|
| RAID 0 | Striping | 2 | No | 0 | ★★★ |
| RAID 1 | Mirroring | 2 | Yes | 1 | ★★ |
| RAID 5 | Striping + Parity | 3 | Yes | 1 | ★★ |
| RAID 6 | Striping + Double Parity | 4 | Yes | 2 | ★★ |
| RAID 0+1 | Stripe + Mirror | 4 | Yes | 1 | ★★★ |
| RAID 1+0 | Mirror + Stripe | 4 | Yes | 1* | ★★★ |
| JBOD | Spanning | 1 | No | 0 | ★ |
* RAID 1+0 tolerates 1 failure per mirror pair. If both drives of the same pair fail, the volume is lost.
RAID levels in detail
Click on a RAID type to discover how it works, its advantages and common failures.
RAID 0
StripingData distribution (striping) across multiple drives with no redundancy. Maximum performance, but the loss of a single drive causes total data loss.
Learn moreRAID 1
MirroringComplete data duplication (mirroring) across two or more drives. Full redundancy: if one drive fails, the mirror takes over.
Learn moreRAID 5
Distributed ParityData distribution with distributed parity across at least 3 drives. Combines performance and security, tolerates the loss of one drive.
Learn moreRAID 6
Double ParitySimilar to RAID 5 with double parity. Tolerates the simultaneous failure of two drives, ideal for critical environments.
Learn moreRAID 0+1
Mirror + StripeRAID 0 + RAID 1 combination: data is first distributed by striping, then duplicated in a mirror. Performance and redundancy.
Learn moreRAID 1+0
Stripe + MirrorRAID 1 + RAID 0 combination: each pair of drives is mirrored, then the pairs are striped. Better fault tolerance than RAID 0+1.
Learn moreJBOD
No RAIDJust a Bunch Of Disks — drives are concatenated into a single volume with no redundancy or striping. No protection against failures.
Learn moreSpare
Hot SpareA hot spare drive waits in reserve. When an active drive fails, the spare takes over automatically and starts a rebuild.
Learn more